JP4525836B2 - Optical device, wavelength tunable filter, wavelength tunable filter module, and optical spectrum analyzer - Google Patents

Description

  The present invention relates to an optical device, a wavelength tunable filter, a wavelength tunable filter module, and an optical spectrum analyzer.

As an optical device, for example, a wavelength tunable filter (Optical Tunable Filter) that separates only light having a specific wavelength from light having a plurality of wavelengths is known (for example, see Patent Document 1).
For example, in the wavelength tunable filter according to Patent Document 1, a movable portion that is plate-shaped and is displaceable in the thickness direction is disposed substantially parallel to the support substrate, and the surface of the movable portion on the support substrate side is arranged. A reflective film is provided on each of the movable substrate side surface (opposing surface) of the support substrate.

  In addition, a drive electrode is provided on the support substrate, and by generating a potential difference between the drive electrode and the movable part, an electrostatic attractive force is generated therebetween, and the movable part is displaced. The distance between the two reflecting films is variable due to the displacement of the movable part. When light having a plurality of wavelengths enters the gap, only light having a wavelength corresponding to the distance of the gap is emitted to the outside due to the interference action.

  In order to suitably generate such an interference action, it is necessary to accurately set the distance between the movable part and the support substrate or to increase the parallelism between the movable part and the support substrate. . Therefore, a plurality of drive electrodes are provided, and a plurality of detection electrodes are provided on the support substrate so as to correspond to the drive electrodes, and the movable portion and the support substrate are parallel based on the capacitance between the detection electrodes and the movable portion. It is necessary to detect the degree and the distance between the movable part and the support substrate.

However, in the wavelength tunable filter of Patent Document 1, since the surface of the support substrate on the movable part side is a plane, the detection electrode must be provided on the same plane as the drive electrode, and the drive electrode and the detection When the distance between the electrodes is small, the coupling capacitance generated between them becomes large, and it is difficult to accurately perform the detection.
If the distance between the drive electrode and the detection electrode is increased in order to reduce the coupling capacitance generated between the drive electrode and the detection electrode, the area of the drive electrode must be reduced accordingly. The driving voltage becomes high.

US Pat. No. 6,747,775

  An object of the present invention is to provide an optical device, a wavelength tunable filter, a wavelength tunable filter module, and an optical spectrum analyzer that have excellent optical characteristics while reducing drive voltage.

Such an object is achieved by the present invention described below.
The optical device of the present invention includes a fixed portion having a first light reflecting portion,
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. It is characterized by that.

Thereby, the distance between the drive electrode and the detection electrode can be increased. As a result, the coupling capacitance generated between the drive electrode and the detection electrode is reduced, and the electrostatic capacitance between the movable portion and the detection electrode is detected with high accuracy, and the movable portion is desired based on the detection result. Can be accurately displaced to the position and posture. At that time, it is possible to arrange the drive electrode and the detection electrode so as to overlap each other in plan view, so that the drive electrode is increased in area, the drive voltage is reduced, and the detection electrode is increased in area. Therefore, the detection accuracy can be improved. Thus, the optical device of the present invention can obtain excellent optical characteristics while reducing the driving voltage.
Further, the movable part can be displaced both on the first electrode side and on the second electrode side. Therefore, it is possible to increase the movable range of the movable part while reducing the stress generated in the movable part. As a result, an optical device that can be used for light having a wavelength in a wide range can be provided.
Further, when changing the position and / or posture of the movable part, it is possible to easily set the drive voltage.

Further, the electrostatic capacitance between the one electrode and the movable part is detected, and based on the detection result, a potential difference is generated between the other electrode and the movable part. and causing electrostatic attraction, more varying the position and / or orientation of the movable part may be in use, and the position and orientation of the movable portion more accurately desired.

In the optical device of the present invention, it is preferable that each of the first electrode and the second electrode is composed of a plurality of electrodes.
As a result, the distance between the first light reflecting part and the second light reflecting part and the parallelism between the first light reflecting part and the second light reflecting part are controlled with high accuracy, so that the optical The optical characteristics of the device can be made excellent.

In the optical device of the present invention, the number of electrodes constituting the first electrode and the number of electrodes constituting the second electrode are the same, and each of the electrodes of the first electrode and the second electrode It is preferable to make a pair with each electrode.
Thereby, when changing the attitude | position of a movable part, the setting of a drive voltage can be made easy.
In the optical device according to the aspect of the invention, it is preferable that the shape of the first electrode is similar to the shape of the second electrode.
Thereby, when changing the attitude | position of a movable part, the setting of a drive voltage can be made easier.

In the optical device according to the aspect of the invention, it is preferable that the size of the first electrode is the same as the size of the second electrode.
Thereby, when changing the attitude | position of a movable part, the setting of a drive voltage can be made still easier.
The optical device of the present invention includes a support portion for supporting the movable portion, and a connecting portion for connecting the movable portion and the support portion so that the movable portion can be displaced with respect to the support portion. And it is preferable that the said movable part, the said support part, and the said connection part are integrally formed.
Thereby, the attitude | position of the movable part with respect to a board | substrate can be stabilized more.

In the optical device according to the aspect of the invention, the first substrate on which the movable portion, the support portion, and the connection portion are formed, and one surface side of the first substrate is fixed to the support portion. A second substrate, and a third substrate fixed to the support portion on the other surface side of the first substrate, the first substrate, the second substrate, and An airtight space is formed between each of the third substrates so as to allow displacement of the movable portion, and the first electrode and the first light reflection are formed on the second substrate. It is preferable that a portion is provided, and the second electrode is provided on the third substrate.
Thereby, with a comparatively simple structure, a contact with a movable part and external air is interrupted | blocked, and a movable part can be driven stably.

In the optical device of the present invention, a concave portion is formed on the surface of the second substrate on the first substrate side, and the first light reflecting portion and the first light reflecting portion are formed on the bottom surface of the concave portion. It is preferable that an electrode is provided.
Thereby, without providing a member such as a spacer between the first substrate and the second substrate, the number of components is reduced, and an airtight space is formed between the first substrate and the second substrate. be able to.

In the optical device according to the aspect of the invention, the recess includes a first recess and a second recess formed on the bottom surface of the first recess, and the first electrode includes the second recess. It is preferable that the outer surface is provided on the bottom surface of the first recess, and the first light reflecting portion is provided on the bottom surface of the second recess.
Thereby, even if the distance between the first light reflecting portion and the second light reflecting portion is increased and the wavelength of light causing interference is increased, the distance between the first electrode and the movable portion is increased. The drive voltage can be reduced by reducing the driving voltage.

In the optical device according to the aspect of the invention, it is preferable that the first electrode is provided so as to surround the first light reflecting portion.
Thereby, the attitude | position of the movable part with respect to a board | substrate can be detected easily and correctly.
In the optical device of the present invention, it is preferable that the first substrate is made of silicon as a main material.
As a result, stable driving is possible, and optical characteristics and durability can be further improved.

In the optical device of the present invention, it is preferable that at least one of the second substrate and the third substrate is made of glass as a main material.
Accordingly, light is incident from the outside between the first light reflecting portion and the second light reflecting portion via the second substrate and / or the third substrate, or the light is incident on the first light reflecting portion. And the second light reflecting portion can be emitted to the outside via the second substrate and / or the third substrate. Furthermore, visibility can be improved, and defects such as contamination of foreign matter inside the device can be easily determined.

In the optical device according to the aspect of the invention, it is preferable that at least one of the second substrate and the third substrate is composed mainly of glass containing alkali metal ions.
Thereby, when the first substrate is composed of silicon as a main material, the first substrate and the second substrate and / or the third substrate can be easily and firmly bonded to each other by anodic bonding. .

In the optical device according to the aspect of the invention, it is preferable that the first substrate is formed by processing one Si layer of the SOI wafer.
Thereby, a movable part, a support part, and a connection part can be made more highly accurate comparatively easily.
In the optical device according to the aspect of the invention, it is preferable that at least one of the first light reflecting portion and the second light reflecting portion is formed of a dielectric multilayer film.
Thereby, loss of light at the time of light interference between the first light reflection part and the second light reflection part can be prevented, and the optical characteristics can be improved.

In the optical device of the present invention, in the state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode, the first electrode and the first electrode It is preferable that the second electrode is provided symmetrically via the movable part.
Thereby, when changing the position and / or attitude | position of a movable part, the setting of a drive voltage can be made easier.

The wavelength tunable filter of the present invention includes a fixed portion having a first light reflecting portion,
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. It is characterized by that.

  Thereby, the distance between the drive electrode and the detection electrode can be increased. As a result, the coupling capacitance generated between the drive electrode and the detection electrode is reduced, and the electrostatic capacitance between the movable portion and the detection electrode is detected with high accuracy, and the movable portion is desired based on the detection result. Can be accurately displaced to the position and posture. At that time, it is possible to arrange the drive electrode and the detection electrode so as to overlap each other in plan view, so that the drive electrode is increased in area, the drive voltage is reduced, and the detection electrode is increased in area. Therefore, the detection accuracy can be improved. Thus, the wavelength tunable filter of the present invention can obtain excellent optical characteristics while reducing the drive voltage.

The wavelength tunable filter module of the present invention includes a fixed portion having a first light reflecting portion,
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. It is characterized by that.

  Thereby, the distance between the drive electrode and the detection electrode can be increased. As a result, the coupling capacitance generated between the drive electrode and the detection electrode is reduced, and the electrostatic capacitance between the movable portion and the detection electrode is detected with high accuracy, and the movable portion is desired based on the detection result. Can be accurately displaced to the position and posture. At that time, it is possible to arrange the drive electrode and the detection electrode so as to overlap each other in plan view, so that the drive electrode is increased in area, the drive voltage is reduced, and the detection electrode is increased in area. Therefore, the detection accuracy can be improved. Thus, the wavelength tunable filter module of the present invention can obtain excellent optical characteristics while reducing the drive voltage.

An optical spectrum analyzer of the present invention includes a fixed portion having a first light reflecting portion,
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. It is characterized by that.

  Thereby, the distance between the drive electrode and the detection electrode can be increased. As a result, the coupling capacitance generated between the drive electrode and the detection electrode is reduced, and the electrostatic capacitance between the movable portion and the detection electrode is detected with high accuracy, and the movable portion is desired based on the detection result. Can be accurately displaced to the position and posture. At that time, it is possible to arrange the drive electrode and the detection electrode so as to overlap each other in plan view, so that the drive electrode is increased in area, the drive voltage is reduced, and the detection electrode is increased in area. Therefore, the detection accuracy can be improved. Thus, the optical spectrum analyzer of the present invention can obtain excellent optical characteristics while reducing the drive voltage.

It is a disassembled perspective view which shows embodiment of the optical device (wavelength variable filter) of this invention. It is a top view which shows the optical device shown in FIG. It is the sectional view on the AA line in FIG. It is a figure for demonstrating the drive electrode and detection electrode of the optical device shown in FIG. It is a block diagram which shows the structure of the control system of the optical device shown in FIG. It is a figure for demonstrating the manufacturing method of the optical device shown in FIG. It is a figure for demonstrating the manufacturing method of the optical device shown in FIG. It is a figure for demonstrating the manufacturing method of the optical device shown in FIG. It is a figure for demonstrating the manufacturing method of the optical device shown in FIG. It is a figure for demonstrating the manufacturing method of the optical device shown in FIG. It is a figure which shows embodiment of the wavelength tunable filter module of this invention. It is a figure which shows embodiment of the optical spectrum analyzer of this invention.

Hereinafter, an optical device, a wavelength tunable filter, a wavelength tunable filter module, and an optical spectrum analyzer according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
1 is an exploded perspective view showing an embodiment of the optical device of the present invention, FIG. 2 is a plan view of the optical device shown in FIG. 1, FIG. 3 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a diagram for explaining drive electrodes and detection electrodes of the optical device shown in FIG. 1, and FIG. 5 is a block diagram showing a configuration of a control system of the optical device shown in FIG. In the following description, the upper side in FIG. 1 is referred to as “upper”, the lower side is referred to as “lower”, the front side in FIG. 2 and FIG. 4 is “upper”, the rear side in FIG. The right side is called “right”, the left side is called “left”, the upper side in FIG. 3 is called “upper”, the lower side is called “lower”, the right side is called “right”, and the left side is called “left side”.

The optical device 1 shown in FIG. 1 is, for example, a wavelength tunable filter that receives light and emits only light (interference light) corresponding to a specific wavelength among the wavelengths of the light by interference action. The optical device 1 can also be used as other optical devices such as an optical switch and an optical attenuator.
In such an optical device 1, as shown in FIGS. 1 and 3, the second substrate 3 and the third substrate 4 are bonded via the first substrate 2. Between the first substrate 2 and the second substrate 3, there is a first gap G1 for causing light interference, and an electrostatic for generating an electrostatic attractive force when the first gap G1 is reduced. A second gap G2, which is a gap, is formed. On the other hand, a third gap G3, which is an electrostatic gap for generating electrostatic attraction when the first gap G1 is enlarged, is formed between the first substrate 2 and the third substrate 4. ing. Here, each of the second gap G2 and the third gap G3 can also function as a detection electrode for detecting the capacitance between the second gap G2 and the third gap G3.

In such an optical device 1, when the light L is incident on the first gap G1, only light having a wavelength corresponding to the size of the first gap G1 is emitted due to the interference action. Hereinafter, each configuration of the optical device 1 will be sequentially described in detail.
The first substrate 2 has light transparency and conductivity, and is made of, for example, silicon. The first substrate 2 supports the movable portion 21, the support portion 22, and the movable portion 21 for making the first gap G1 between the first substrate 2 and the second substrate 3 variable. It has the connection part 23 which connects these so that it can displace to the up-down direction with respect to the part 22. FIG. These are integrally formed by forming an opening 24 having a different shape in the first substrate 2.

The movable portion 21 has a plate shape and is located in a substantially central portion of the first substrate 2 in a plan view and has a circular shape. Such a movable part 21 is opposed to the second substrate 3 with a gap, and is provided so as to be displaceable in the thickness direction. Needless to say, the shape, size, and arrangement of the movable portion 21 are not particularly limited to the illustrated shapes.
The thickness (average) of the movable portion 21 is appropriately selected according to the constituent material, application, and the like, and is not particularly limited, but is preferably about 1 to 500 μm, and more preferably about 10 to 100 μm.

  Further, the movable part 21 is a movable part that reflects light with a relatively high reflectance as a second light reflecting part on the surface facing the second substrate 3 (that is, the lower surface of the movable part 21). A reflective film (HR coat) 25 is formed, and a movable antireflection film (AR) that suppresses reflection of light on the surface opposite to the side facing the second substrate 3 (that is, the upper surface of the movable portion 21). Coat) 26 is formed.

  As shown in FIG. 3, the movable reflective film 25 allows light incident on the first gap G1 from below the optical device 1 to pass through the fixed reflective film 35, which is a first light reflecting portion described later, a plurality of times. It is for reflection. As shown in FIG. 3, the movable antireflection film 26 reflects light incident on the first gap G1 from below the optical device 1 downward in the figure at the interface between the upper surface of the first substrate 2 and the outside air. It is for preventing.

  The movable reflective film (dielectric multilayer film) 25 and the movable antireflection film 26 are not particularly limited as long as necessary optical characteristics can be obtained, but those made of a dielectric multilayer film are preferable. That is, the movable reflective film (dielectric multilayer film) 25 and the movable antireflection film 26 are preferably formed by alternately laminating a plurality of high refractive index layers and low refractive index layers. Thereby, loss of light at the time of interference of light between the movable reflective film 25 and the fixed reflective film 35 can be prevented, and optical characteristics can be improved.

The material constituting the high refractive index layer is not particularly limited as long as it can obtain the optical characteristics necessary for the movable reflective film 25 and the movable antireflection film 26, but in the visible light region and the infrared light region. When used, Ti ₂ O, Ta ₂ O ₅ , niobium oxide, and the like can be used. When used in the ultraviolet region, Al ₂ O ₃ , HfO ₂ , ZrO ₂ , ThO _{2, and the} like can be given. In the present embodiment, since the first substrate 2 is made of silicon, infrared light is used for the optical device 1. Therefore, Ti ₂ O, Ta ₂ O ₅ , niobium oxide, or the like is preferably used as a material constituting the high refractive index layer.

The material constituting the low refractive index layer is not particularly limited as long as it can obtain the optical characteristics necessary for the movable reflective film 25 and the movable antireflection film 26. For example, MgF ₂ , SiO _{2, and the} like are used. Can be mentioned. In particular, as a constituent material of the low refractive index layer, a material mainly composed of SiO ₂ is preferably used.
The number and thickness of the high refractive index layer and the low refractive index layer constituting the movable reflective film 25 and the movable antireflection film 26 are set according to the required optical characteristics. In general, when a reflective film is composed of a multilayer film, the number of layers required to obtain its optical characteristics is 12 or more, and when an antireflection film is composed of a multilayer film, the number of layers necessary for the optical characteristics is About 4 layers.

When the movable reflective film 25 has insulating properties, a short circuit due to contact between the movable portion 21 and the first electrode 33 can be prevented. That is, when an insulating film is provided on the surface of the movable portion 21 on the second substrate 3 side, a short circuit due to contact between the movable portion 21 and the first electrode 33 can be prevented.
In this case, since the movable reflection film 25 also serves as an insulating film, a short circuit due to contact between the movable portion 21 and the first electrode 33 can be prevented with a simpler configuration. Further, since the movable antireflection film 26 also serves as an insulating film, a short circuit due to contact between the movable portion 21 and the second electrode 43 can be prevented with a simpler configuration.

A support portion 22 is formed so as to surround such a movable portion 21, and the movable portion 21 is supported by the support portion 22 via a connecting portion 23.
A plurality (four in the present embodiment) of the connecting portions 23 are provided at equal intervals in the circumferential direction around the movable portion 21 described above. The connecting portion 23 has elasticity (flexibility), so that the movable portion 21 is spaced substantially parallel to the second substrate 3 in the thickness direction (up and down). Can be displaced. The number, position, and shape of the connecting portions 23 are not limited to those described above as long as the movable portion 21 can be displaced with respect to the support portion 22.

The first substrate 2 is provided with openings 27a and 27b for accessing later-described extraction electrodes 38a and 38b from the outside. The openings 27a and 27b also function as pressure release openings that prevent the occurrence of a pressure difference with the outside in the space between the first substrate and the second substrate in the manufacturing process of the optical device 1. To do.
In such a first substrate 2, it is preferable that the movable portion 21, the support portion 22, and the connecting portion 23 are integrally formed. Thereby, the attitude | position of the movable part 21 with respect to the 2nd board | substrate 3 can be stabilized more.

In that case, if the movable part 21, the support part 22, and the connecting part 23 are each composed of silicon as a main material, the optical characteristics and the durability can be further improved.
In particular, when the movable portion 21, the support portion 22, and the connecting portion 23 are formed by processing one Si layer of the SOI wafer, the movable portion 21 and the supporting portion 22 are relatively easily connected. The part 23 can be made more accurate.

The second substrate 3 is bonded to the first substrate 2 on the lower surface of the support portion 22.
The second substrate 3 has optical transparency, and the second substrate 3 has a second gap between the first substrate 2 and the second substrate 3 on one surface side. A first recess 31 for forming G2 and a second recess 32 for forming a first gap G1 between the first substrate 2 and the second substrate 3 inside the first recess 31. And are formed.

The constituent material of the second substrate 3 is not particularly limited as long as it has light transmittance with respect to the wavelength of light to be used. For example, soda glass, crystalline glass, quartz glass, lead glass, potassium Examples thereof include various glasses such as glass, borosilicate glass, sodium borosilicate glass, and alkali-free glass, and silicon.
Among these, as a constituent material of the 2nd board | substrate 3, the glass containing alkali metals (mobile ion) like sodium (Na) or potassium (K) is preferable, for example. Thereby, when the 1st board | substrate 2 is comprised, for example with silicon | silicone, the 1st board | substrate 2 and the 2nd board | substrate 3 can be joined simply and firmly by anodic bonding.

In particular, when the first substrate 2 and the second substrate 3 are bonded by anodic bonding, the difference between the thermal expansion coefficient of the first substrate 2 and the thermal expansion coefficient of the second substrate 3 is as small as possible. More specifically, it is preferably 50 × 10 ⁻⁷ ° C. ⁻¹ or less.
Thereby, even if the first substrate 2 and the second substrate 3 are exposed to a high temperature during anodic bonding, the stress generated between the first substrate 2 and the second substrate 3 is reduced, and the first substrate 2 and the second substrate 3 are reduced. Damage to the substrate 2 or the second substrate 3 can be prevented.

Therefore, it is preferable to use soda glass, potassium glass, sodium borosilicate glass, or the like as the constituent material of the second substrate 3. For example, Pyrex glass (registered trademark) manufactured by Corning, Inc. is preferably used.
In addition, the thickness (average) of the second substrate 3 is appropriately selected depending on the constituent material, application, and the like, and is not particularly limited, but is preferably about 10 to 2000 μm, and more preferably about 100 to 1000 μm. .

  The first concave portion 31 has a circular outer shape, and is disposed at a position corresponding to the movable portion 21, the connecting portion 23, and the opening portion 24 described above. On the bottom surface of the first recess 31, an annular first electrode 33 and an insulating film 34 are stacked in this order at a position corresponding to the outer peripheral portion of the movable portion 21. In this way, the first electrode 33 is provided on the installation surface of the second substrate 3 on the movable part 21 side.

  The first electrode 33 has a substantially annular shape as a whole, and is composed of two first electrodes 33a and 33b which are divided into two. The first electrodes 33a and 33b are connected to the energization circuit 10 as shown in FIG. Thereby, it is possible to generate a potential difference between the first electrode 33 and the movable part 21 and to detect the capacitance between the first electrode 33 and the movable part 21. . The energization circuit 10 will be described in detail later.

Each of the first electrodes 33 a and 33 b is provided so as to surround the second recess 32. Thereby, the electrostatic attractive force between each 1st electrode 33a, 33b and the movable part 21 can be balanced easily. As a result, the posture of the movable portion 21 with respect to the second substrate 3 can be further stabilized.
The constituent material of the first electrode 33 (each of the first electrodes 33a and 33b) is not particularly limited as long as it has conductivity. For example, Cr, Al, Al alloy, Ni, Examples thereof include metals such as Zn and Ti, resins in which carbon and titanium are dispersed, silicon such as polycrystalline silicon (polysilicon) and amorphous silicon, silicon nitride, a transparent conductive material such as ITO, and Au.
The thickness (average) of the first electrode 33 is appropriately selected depending on the constituent material, application, and the like, and is not particularly limited, but is preferably about 0.1 to 5 μm.

The insulating film 34 has the same shape as the first electrode 33, and has a function of preventing a short circuit due to contact between the movable portion 21 and the first electrode 33.
A second gap G <b> 2 is formed as an electrostatic gap (drive gap) for driving the movable portion 21 in the space in the first recess 31. That is, the second gap G <b> 2 is formed between the movable portion 21 and the first electrode 33.

The size of the second gap G2 (that is, the distance between the movable portion 21 and the first electrode 33) is appropriately selected according to the application and the like, and is not particularly limited, but is about 0.5 to 20 μm. Is preferred.
The second concave portion 32 has a circular outer shape, is substantially concentric with the first concave portion 31 described above, and has an outer diameter smaller than the outer diameters of the first concave portion 31 and the movable portion 21. A fixed reflection film 35 having a substantially circular shape is provided on the bottom surface of the second recess 32 (the surface of the second substrate 3 on the movable portion 21 side).

  As described above, the fixed reflection film 35 reflects light incident on the first gap G1 from below the optical device 1 with the movable reflection film 25 a plurality of times as shown in FIG. It is. That is, the fixed reflective film 35 corresponds to the size of the first gap G1 (that is, the distance between the fixed reflective film 35 and the movable reflective film 25) in cooperation with the movable reflective film 25 described above. Wavelength light can be made to interfere. The size of the first gap G1 is larger than the size of the second gap G2 described above.

The size of the first gap G1 is appropriately selected according to the application and is not particularly limited, but is preferably about 1 to 100 μm.
As described above, when the fixed reflective film 35 is provided on the bottom surface of the second recess 32, the depth of the second recess 32 is independent of the distance between the first electrode 33 and the movable portion 21. The usable wavelength band can be set according to the size. Therefore, the drive voltage can be reduced even when various usable wavelength bands are set.

  Note that the second recess 32 may be omitted. In this case, as long as the optical characteristics of the optical device 1 are not impaired, the first electrode can be provided over almost the entire bottom surface of the first recess 31, and the fixed reflective film 35 can be provided thereon. Thereby, the area of a detection electrode or a drive electrode can be enlarged, the detection accuracy of the electrostatic capacitance between the movable part 21 and a detection electrode can be improved, or a drive voltage can be reduced. Further, the constituent material of the fixed reflection film is made of a conductive material, so that the fixed reflection film is provided almost over the entire bottom surface of the first recess 31, and the movable reflection film is the first electrode (detection electrode or drive electrode). Can also be used. This also makes it possible to increase the area of the detection electrode and the drive electrode, improve the detection accuracy of the capacitance between the movable portion 21 and the detection electrode, and reduce the drive voltage.

Further, the second substrate 3 has third recesses 37a, 37b, third recesses 37a, 37b, and first recess 31 in order to bring out the first electrodes 33a, 33b described above to the outside. Grooves 36a and 36b are formed to communicate with each other.
The depth of the groove 36a and the third recess 37a is substantially the same as the depth of the first recess 31, and a lead electrode 38a connected to the first electrode 33a is provided on the bottom surface thereof. It has been. Similarly, the depth of the groove 36b and the third recess 37b is substantially equal to the depth of the first recess 31, and is connected to the first electrode 33b on the bottom surface thereof. An extraction electrode 38b is provided.

  As the constituent material of the extraction electrode 38 (extraction electrodes 38a and 38b), the same material as that of the first electrode 33 described above can be used. For example, metal such as Cr, Al, Al alloy, Ni, Zn, Ti, resin in which carbon or titanium is dispersed, silicon such as polycrystalline silicon (polysilicon), amorphous silicon, silicon nitride, ITO, etc. Transparent conductive materials such as Au.

Further, the thickness (average) of the extraction electrode 38 is appropriately selected depending on the constituent material, application, etc., and is not particularly limited, but is preferably about 0.1 to 5 μm. The extraction electrode 38a is preferably formed integrally with the first electrode 33a described above, and the extraction electrode 38b is formed integrally with the first electrode 33b described above.
A fixed antireflection film 39 is formed on the other surface of the second substrate 3 (that is, the surface opposite to the surface on which the first concave portion 31 and the like described above are formed).

As shown in FIG. 3, the fixed antireflection film 39 reflects light irradiated from below the optical device 1 toward the first gap G <b> 1 downward in the drawing at the interface between the lower surface of the second substrate 3 and the outside air. This is to prevent the problem. The configurations of the fixed reflection film 35 and the fixed antireflection film 39 are the same as those of the movable reflection film 25 and the movable antireflection film 26 described above.
The third substrate 4 bonded to the first substrate 2 on the side opposite to the second substrate 3 also has light transmittance. The third substrate 4 is provided with a concave portion 41 for forming a third gap G3 between the first substrate 2 and the third substrate 4 on one surface side thereof.

  Thus, a space is formed between the first substrate 2 and each of the second substrate 3 and the third substrate 4 so as to allow the displacement of the movable portion 21. It can be formed as an airtight space. In this way, with a relatively simple configuration, the contact between the movable portion 21 and the outside air can be blocked, and the movable portion 21 can be driven stably. In the present embodiment, the portion other than the movable portion 21 of the first substrate 2 and the second substrate 3 and the third substrate 4 constitute a fixed portion, whereas the movable portion 21 is movable. ing.

In the present embodiment, since the fixed reflective film 35 and the first electrode 33 are provided on the bottom surface of the recess formed in the second substrate 3 as in the present embodiment, the first substrate 2 Without providing a member such as a spacer between the first substrate 2 and the second substrate 3, the number of components is reduced, and the airtight space as described above is formed between the first substrate 2 and the second substrate 3. be able to.
The constituent material of the third substrate 4 is not particularly limited as long as it has light transmittance with respect to the wavelength of light to be used, and the same constituent material as that of the second substrate 3 described above is used. be able to. Therefore, when glass containing an alkali metal is used as the constituent material of the third substrate 4, the third substrate 4 and the first substrate 2 can be joined by anodic bonding in the same manner as the second substrate 3. it can.

  When at least one of the second substrate 3 and the third substrate 4 is made of glass as a main material, light is fixedly reflected from the outside via the second substrate 3 and / or the third substrate 4. Incident light is incident between the film 35 and the movable reflective film 25, or light is emitted from between the fixed reflective film 35 and the movable reflective film 25 to the outside via the second substrate 3 and / or the third substrate 4. Can be.

The thickness (average) of the third substrate 4 is appropriately selected depending on the constituent material, application, etc., and is not particularly limited, but is preferably about 10 to 2000 μm, and more preferably about 100 to 1000 μm. .
The concave portion 41 has a circular outer shape, and is disposed at a position corresponding to the movable portion 21, the coupling portion 23, and the opening portion 24, similar to the first concave portion 31 described above. Further, the depth and the outer diameter of the recess 41 are substantially equal to the depth and the outer diameter of the first recess 31 described above. Further, an annular second electrode 43 (second electrode) and an insulating film 44 are laminated in this order on the bottom surface of the first recess 31 at a position corresponding to the outer peripheral portion of the movable portion 21. Yes. In this way, the second electrode 43 is provided on the installation surface of the third substrate 4 on the movable part 21 side.

  The second electrode 43 has a substantially annular shape as a whole, and is composed of two second electrodes 43a and 43b that bisect the same as the first electrode 33 described above. The second electrodes 43a and 43b are connected to the energizing circuit 10 in the same manner as the first electrodes 33a and 33b. Thereby, it is possible to generate a potential difference between the second electrode 43 and the movable part 21 and to detect the electrostatic capacitance between the second electrode 43 and the movable part 21. .

  As described above, when at least one of the first electrode and the second electrode is provided in plural, the posture of the movable portion 21 can be changed or the posture of the movable portion 21 can be detected. When changing the posture of the movable portion 21, for example, substantially the same voltage is applied to each of the first electrodes 33a and 34a or each of the second electrodes 43a and 43b, so that the fixed reflective film 35 and the movable reflective film 25 are The movable portion 21 can be displaced so as to maintain the parallelism of the first electrode 33a and the second electrode 43a and 43b by applying different voltages to the fixed reflection film 35. In contrast, the movable portion 21 can be displaced so that the movable reflective film 25 is inclined. Further, not only the position of the movable part 21 but also the posture of the movable part 21 can be detected.

  In particular, in the present embodiment, since a plurality of first electrodes and a plurality of second electrodes are provided, the posture of the movable portion 21 can be detected with higher accuracy. Further, for example, a potential difference is generated only in the first electrode 33a and the second electrode 43b, a part of the movable part 21 is displaced toward the first electrode 33, and the other part of the movable part 21 is moved to the second electrode. It can be displaced toward the electrode 43 side. As a result, the posture of the movable part 21 can be changed in a wider range.

Further, since the number of the first electrodes and the number of the second electrodes are the same, and each first electrode and each second electrode form a pair, the posture of the movable portion 21 is changed. At this time, the drive voltage can be easily set. Moreover, when detecting the attitude | position and position of the movable part 21, the structure and process of the detection part 12 mentioned later can be simplified.
Further, since the shape of the first electrode 33 is similar to the shape of the second electrode 43, the drive voltage can be set more easily when the posture of the movable portion 21 is changed. Moreover, when detecting the attitude | position and position of the movable part 21, the structure and process of the detection part 12 mentioned later can be simplified.
In addition, since the size (area) of the first electrode 33 is the same as the size (area) of the second electrode 43, the drive voltage can be set more easily when the posture of the movable portion 21 is changed. Can be. Moreover, when detecting the attitude | position and position of the movable part 21, the structure and process of the detection part 12 mentioned later can be simplified.

The constituent material of the second electrode 43 (each of the second electrodes 43a and 43b) is not particularly limited as long as it has conductivity, and the constituent material of the first electrode 33 described above can be used. Similar ones can be used.
The thickness (average) of the second electrode 43 is appropriately selected depending on the constituent material, application, and the like and is not particularly limited, but is preferably about 0.1 to 5 μm.

The insulating film 44 has the same shape as the second electrode 43 and has a function of preventing a short circuit due to contact between the movable portion 21 and the second electrode 43.
A third gap G <b> 3 is formed as an electrostatic gap (drive gap) for driving the movable portion 21 in the space in the recess 41. That is, the third gap G3 is formed between the movable portion 21 and the second electrode 43.

  In a state where no potential difference is generated between the movable part 21 and the first electrode 33 and the second electrode 43, the distance (second gap G2) between the first electrode 33 and the movable part 21 is The distance between the second electrode 43 and the movable portion 21 (third gap G3) is preferably substantially equal. Thereby, when changing the position and / or attitude | position of the movable part 21, the setting of a drive voltage can be made easy. Moreover, when detecting the attitude | position and position of the movable part 21, the structure and process of the detection part 12 mentioned later can be simplified.

  In this case, it is preferable that the first electrode 33 and the second electrode 43 are provided symmetrically via the movable portion 21 in a state where the potential difference is not generated. Thereby, when changing the position and / or attitude | position of the movable part 21, the setting of a drive voltage can be made easier. Moreover, when detecting the attitude | position and position of the movable part 21, the structure and process of the detection part 12 mentioned later can be simplified.

The size of the third gap G3 (that is, the distance between the movable portion 21 and the second electrode 43) is appropriately selected depending on the application and the like, and is not particularly limited, but is about 0.5 to 20 μm. Is preferred.
A fixed antireflection film 42 having a substantially circular shape is provided on the bottom surface of the recess 41 at the center thereof. That is, the above-described second electrode 43 is provided on the bottom surface (installation surface) of the recess 41 so as to surround the fixed antireflection film 42.

In the fixed antireflection film 42, as shown in FIG. 3, light incident on the first gap G1 from below the optical device 1 is reflected downward in the figure at the interface between the lower surface of the third substrate 4 and the outside air. It is for preventing. The configuration of the fixed antireflection film 42 is the same as that of the movable antireflection film 26 described above.
The third substrate 4 is provided with openings 47a and 47b for accessing the extraction electrodes 38a and 38b described above from the outside. Note that the above-described extraction of the second electrode 43 is extracted from an extraction unit (not shown).

A fixed antireflection film 49 is formed on the other surface of the third substrate 4 (that is, the surface opposite to the surface on which the above-described concave portion 41 and the like are formed).
In the fixed antireflection film 49, as shown in FIG. 3, light incident on the third gap G3 from below the optical device 1 is reflected downward in the figure at the interface between the upper surface of the third substrate 4 and the outside air. It is for preventing. The configuration of the fixed antireflection film 49 is the same as the configuration of the movable antireflection film 26 described above.

Here, the energization circuit 10 will be described more specifically based on FIG.
As shown in FIG. 5, the energization circuit 10 is movable with the power supply unit 11 for applying a voltage to the electrodes 33a, 33b, 43a, 43b and the electrodes 33a, 33b, 43a, 43b. A detection unit 12 for detecting capacitance between the unit 21, a switching unit 13 for switching connection states between the electrodes 33 a, 33 b, 43 a, 43 b and the power supply unit 11 and the detection unit 12; And a control unit 14 for controlling the driving of the power supply unit 11 and the switching unit 13 based on the detection result.

  The power supply unit 11 can generate an arbitrary potential difference between the electrodes 33 a, 33 b, 43 a, 43 b and the movable unit 21. That is, in the optical device 1, a voltage is selectively applied to the first electrode 33 and the second electrode 43, so that the first electrode 33 and / or the second electrode 43 and the movable portion 21 are interposed. It is possible to generate a potential difference. Thereby, the movable part 21 can be made into a desired position and attitude | position more reliably.

The detection part 12 can detect between each electrode 33a, 33b, 43a, 43b and the movable part 21 independently. Thereby, a potential difference that allows the movable portion 21 to have a desired position and posture can be generated between the electrodes 33 a, 33 b, 43 a, 43 b and the movable portion 21.
The switching unit 13 can switch the connection state between the electrodes 33a, 33b, 43a, 43b, the power supply unit 11, and the detection unit 12.

  The control unit 14 controls the driving of the power supply unit 11 based on the detection result of the detection unit 12 described above. Thereby, based on the electrostatic capacitance between each electrode 33a, 33b, 43a, 43b and the movable part 21, a potential difference that makes the movable part 21 have a desired position and posture is changed to each electrode 33a, 33b, 43a. , 43b and the movable portion 21 can selectively generate an arbitrary potential difference.

Moreover, the control part 14 switches the said connection state of the switching part 13 mentioned above according to the set wavelength (1st gap G1), for example.
The operation (action) of the optical device 1 having such a configuration will be described.
The energization circuit 10 described above detects the electrostatic capacitance between one of the first electrode 33 and the second electrode 43 and the movable portion 21, and based on the detection signal (detection result), A potential difference is generated between the other electrode of the first electrode 33 and the second electrode 43 and the movable portion 21.

  More specifically, when the set wavelength is smaller than the first gap G1 when no voltage is applied, the first electrode 33 functions as a drive electrode, and the second electrode 43 functions as a detection electrode. Let In this case, a voltage is applied between the movable portion 21 and the first electrode 33 by the energization circuit 10, and the movable portion 21 and the first electrode 33 are charged with opposite polarities, and a Coulomb force is generated between the two. (Electrostatic attractive force) is generated.

  Due to the Coulomb force, the movable portion 21 moves (displaces) downward toward the first electrode 33 and stops at a position where the elastic force of the connecting portion 23 and the Coulomb force are balanced. Thereby, the magnitude | size of the 1st gap G1 and the 2nd gap G2 changes. At this time, the posture (inclination) of the movable portion 21 is determined by the balance between the voltage applied to the first electrode 33a and the voltage applied to the first electrode 33b.

  Further, when the set wavelength is larger than the first gap G1 when no voltage is applied, the first electrode 33 functions as a detection electrode, and the second electrode 43 functions as a drive electrode. A voltage is applied between the movable portion 21 and the second electrode 43 by the energization circuit 10, and the movable portion 21 and the second electrode 43 are charged with opposite polarities, and a Coulomb force (electrostatic force) is generated between the two. Attractive force).

  Due to the Coulomb force, the movable portion 21 moves (displaces) upward toward the second electrode 43 and stops at a position where the elastic force of the connecting portion 23 and the Coulomb force are balanced. Thereby, the magnitude | size of the 1st gap G1 and the 2nd gap G2 changes. At this time, the attitude (inclination) of the movable portion 21 is determined by the balance between the voltage applied to the second electrode 43a and the voltage applied to the second electrode 43b.

On the other hand, as shown in FIG. 3, when the light L is irradiated from below the optical device 1 toward the first gap G1, the light L is emitted from the fixed antireflection film 39, the second substrate 3, and the fixed reflection film 35. And enters the first gap G1. At this time, the light L is incident on the first gap G1 with almost no loss by the fixed antireflection film 39.
The incident light is repeatedly reflected (interfered) between the movable reflective film 25 and the fixed reflective film 35. At this time, the loss of the light L can be suppressed by the movable reflective film 25 and the fixed reflective film 35.

  As described above, in the process of repeatedly reflecting light between the movable reflective film 25 and the fixed reflective film 35, the interference corresponding to the size of the first gap G1 between the movable reflective film 25 and the fixed reflective film 35. Light having a wavelength that does not satisfy the condition is rapidly attenuated, and only light having a wavelength that satisfies the interference condition remains and is finally emitted from the optical device 1. Accordingly, if the first gap G1 is changed (that is, the interference condition is changed) by changing the voltage applied between the movable portion 21, the first electrode 33, and the second electrode 43, the optical device. The wavelength of light passing through 1 can be changed.

As a result of the interference of the light L, the light having a wavelength corresponding to the size of the first gap G1 (interference light) is movable movable film 25, movable part 21, movable antireflection film 26, fixed antireflection film 42, 3 is transmitted through the substrate 4 and the fixed antireflection film 49, and is emitted above the optical device 1. At this time, the movable antireflection film 26 and the fixed antireflection films 42 and 49 emit the interference light to the outside of the optical device 1 with almost no loss.
In the present embodiment, the light incident on the first gap G1 is emitted upward of the optical device 1. However, the light incident on the first gap G1 may be emitted downward of the optical device 1.
In the present embodiment, light is incident on the optical device 1 from below, but light may be incident from above.

  In the optical device 1 as described above, the first electrode 33 facing the surface of the movable portion 21 on the fixed reflection film 35 side with a space therebetween, and the opposite side of the fixed reflection film 35 of the movable portion 21. Of the second electrodes 43 facing the surface of the second electrode 43 with an interval, one electrode functions as a detection electrode for detecting the capacitance between the movable portion 21 and the other electrode, By generating a potential difference with the movable part 21, an electrostatic attractive force is generated between them to function as a drive electrode for changing the position and / or posture of the movable part 21.

  Thereby, the distance between the drive electrode and the detection electrode can be increased. As a result, the coupling capacitance generated between the drive electrode and the detection electrode is reduced, and the electrostatic capacitance between the movable portion 21 and the detection electrode is detected with high accuracy. Based on the detection result, the movable portion 21 is detected. Can be accurately displaced to a desired position and posture. At that time, it is possible to arrange the drive electrode and the detection electrode so as to overlap each other in plan view, so that the drive electrode is increased in area, the drive voltage is reduced, and the detection electrode is increased in area. Therefore, the detection accuracy can be improved. Thus, the optical device 1 of the present invention can obtain excellent optical characteristics while reducing the drive voltage.

  In particular, in the present embodiment, the electrostatic capacitance between the one electrode and the movable portion 21 is detected, and a potential difference is generated between the other electrode and the movable portion 21 based on the detection result. In addition, since an electrostatic attractive force is generated between them to change the position and / or posture of the movable portion 21, the position and posture of the movable portion 21 can be more accurately desired when used.

The capacitance detection as described above is performed only at the time of calibration (calibration), and a potential difference may be generated between the other electrode and the movable portion 21 based on a preset conversion table or the like. Good. In this case, it is also possible to use all of the electrodes 33a, 33b, 43a, and 43b as drive electrodes after calibration.
In addition, each of the first electrode 33 and the second electrode 43 can function as a drive electrode for driving the movable portion 21. That is, the first electrode 33 or the second electrode 43 is configured to be switched alternately when functioning as a detection electrode and when functioning as a drive electrode. Thereby, the movable part 21 can be displaced to both the first electrode 33 side and the second electrode 43 side. Therefore, the movable range of the movable part 21 can be increased while reducing the stress generated in the movable part 21. As a result, the optical device 1 can be used for light having a wavelength in a wide range.
Moreover, the driving force required for the displacement of the movable part 21 can be reduced, and as a result, the driving voltage can be reduced.

<Optical device manufacturing method>
Next, an example of a method for manufacturing the optical device 1 will be described with reference to FIGS.
6-10 is a figure for demonstrating the manufacturing process of the optical device 1. FIG. 6-10 has shown the cross section corresponding to the AA cross section of FIG.
The manufacturing method of the optical device 1 of the present embodiment includes: [A] a step of manufacturing the second substrate 3; [B] a step of bonding the SOI substrate to the second substrate 3; and [C] processing the SOI substrate. Then, the first substrate 2 is manufactured, [D] the third substrate 4 is manufactured, and [E] the third substrate 4 is bonded to the first substrate 2. Hereinafter, each process will be described sequentially.

[A] Production of second substrate 3 -A1-
First, as a substrate for forming the second substrate 3, as shown in FIG. 6A, a light-transmitting substrate 3a is prepared.
As the substrate 3a, a substrate having a uniform thickness and having no deflection or scratch is preferably used. As the constituent material of the substrate 3a, those described in the description of the second substrate 3 can be used. As described above, it is preferable to use glass containing an alkali metal (mobile ion) such as sodium (Na) or potassium (K) as a constituent material of the substrate 3a. Therefore, in the following description, a case where glass containing an alkali metal is used as a constituent material of the substrate 3a will be described.

-A2-
Next, as shown in FIG. 6B, a mask layer 5 is formed (masked) on one surface of the substrate 3a.
Examples of the material constituting the mask layer 5 include metals such as Au / Cr, Au / Ti, Pt / Cr, and Pt / Ti, silicon such as polycrystalline silicon (polysilicon) and amorphous silicon, and silicon nitride. It is done. When silicon is used as the constituent material of the mask layer 5, the adhesion between the mask layer 5 and the substrate 3a is improved. When a metal is used for the constituent material of the mask layer 5, the visibility of the mask layer 5 to be formed is improved.

The thickness of the mask layer 5 is not particularly limited, but is preferably about 0.01 to 1 μm, and more preferably about 0.09 to 0.11 μm. If the mask layer 5 is too thin, the substrate 3a may not be sufficiently protected. If the mask layer 5 is too thick, the mask layer 5 may be easily peeled off due to internal stress of the mask layer 5.
The mask layer 5 can be formed by, for example, a chemical vapor deposition method (CVD method), a vapor deposition method such as a sputtering method or an evaporation method, a plating method, or the like.

-A3-
Next, as shown in FIG. 6C, an opening 51 having a plan view shape corresponding to the plan view shapes of the first recess 31, the groove 36, and the third recess 37 is formed in the mask layer 5. .
More specifically, first, for example, using a photolithography method, a photoresist is applied on the mask layer 5, and exposure and development are performed to form a resist mask having an opening corresponding to the opening 51. Next, the mask layer 5 is etched through the resist mask to remove a part of the mask layer 5, and then the resist mask is removed. In this way, an opening 51 is formed in the mask layer 5. As this etching, for example, dry etching with CF gas, chlorine-based gas, etc., wet etching with hydrofluoric acid + nitric acid aqueous solution, alkaline aqueous solution or the like can be used.

-A4-
Next, one surface of the substrate 3a is etched through the mask layer 5 to form a first recess 31, a groove 36, and a third recess 37, as shown in FIG. 6 (d).
As this etching, a dry etching method or a wet etching method can be used, but a wet etching method is preferably used. Thereby, the 1st recessed part 31 formed can be made into a more ideal column shape. In this case, for example, a hydrofluoric acid-based etchant is preferably used as the etchant for wet etching. Moreover, when alcohol (especially polyhydric alcohol), such as glycerol, is added to etching liquid, the bottom face of the 1st recessed part 31 formed can be made very smooth.

-A5-
Next, after removing the mask layer 5, the plan view shape corresponding to the plan view shape of the second recess 32 as shown in FIG. The mask layer 6 having the openings is formed.
The method for removing the mask layer 5 is not particularly limited. For example, wet etching using an alkaline aqueous solution (for example, tetramethylammonium hydroxide aqueous solution), hydrochloric acid + nitric acid aqueous solution, hydrofluoric acid + nitric acid aqueous solution, CF gas, chlorine gas For example, dry etching or the like can be used.
In particular, when wet etching is used as a method for removing the mask layer 5, the mask layer 5 can be efficiently removed by a simple operation.

-A6-
Next, the substrate 3a is etched through the mask layer 6 using the same method as in the step A4 described above to form the second recess 32 as shown in FIG. A mask layer 6A having an opening in a plan view shape corresponding to the plan view shape of the film 35 is formed. The formation of the mask layer 6A may be performed after removing the mask layer 6 or may be performed without removing the mask layer 6.

-A7-
Next, as shown in FIG. 7A, the fixed reflective film 35 is formed on the bottom surface of the second recess 32 using the mask layer 6 </ b> A.
More specifically, the fixed reflective film 35 is formed on the bottom surface of the second recess 32 by alternately laminating the high refractive index layer and the low refractive layer as described above.
As a method for forming the high refractive index layer and the low refractive index layer, for example, chemical vapor deposition (CVD) or physical chemical vapor deposition (PVD) is preferably used.

-A8-
Next, the mask layer 6A is removed as shown in FIG. 7B by using the same method as in the step-A5- described above.
-A9-
Next, as shown in FIG. 7C, the first electrodes 33a and 33b and the extraction electrodes 38a and 38b are uniformly formed on the surface of the substrate 3a on which the first recesses 31 and the like are formed. A conductive layer 7 for forming is formed.
As a method for forming the conductive layer 7, for example, chemical vapor deposition (CVD) or physical chemical vapor deposition (PVD) is preferably used.
Further, as the constituent material of the conductive layer 7, the constituent material of the first electrode 33 described above can be used.

-A10-
Next, as illustrated in FIG. 7D, unnecessary portions of the conductive layer 7 are removed to form the first electrode 33 and the like, and the insulating film 34 is formed on the first electrode 33. Further, a fixed antireflection film 39 is formed on the surface of the substrate 3a opposite to the side on which the first concave portion 31 and the like are formed.
As a method for removing unnecessary portions of the conductive layer 7, a method similar to the above-described step A3 can be used.

In addition, as the method for forming the first electrode 33, the same method as the method for forming the mask layer 5 described above can be used.
As a method of forming the fixed antireflection film 39, the same method as the method of forming the fixed reflection film 35 described above can be used.
As described above, the second substrate 3 can be manufactured.

[B] Joining of SOI substrate and second substrate 3 -B1-
First, as shown in FIG. 8A, an SOI (Silicon on Insulator) substrate 8 is prepared.
This SOI substrate 8 is formed by laminating these three layers in the order of a base layer 81 made of Si, an insulating layer 82 made of SiO ₂ , and an active layer 83 made of Si. Instead of the SOI substrate 8, an SOS (Silicon on Sapphire) substrate, a silicon substrate, or the like can be used.
The thickness of the SOI substrate 8 is not particularly limited, but the thickness of the active layer 83 is particularly preferably about 10 to 100 μm.

-B2-
Next, prior to the bonding of the SOI substrate 8 and the second substrate 3, as shown in FIG. 8B, the movable reflective film 25 is formed on the surface of the SOI substrate 8 on the active layer 83 side.
As a method of forming the movable reflective film 25, the same method as the method of forming the fixed reflective film 35 described above can be used.

-B3-
Next, as shown in FIG. 8C, the SOI substrate 8 and the second substrate 3 are bonded.
As a bonding method between the SOI substrate 8 and the second substrate 3, for example, anodic bonding, bonding with an adhesive, surface activation bonding, bonding using low melting point glass, or the like can be used, and anodic bonding is used. Is preferred.

  When anodic bonding is used as a bonding method between the SOI substrate 8 and the second substrate 3, for example, first, a negative terminal of a DC power source (not shown) is used as the second substrate 3 and a positive terminal is used as an active layer of the SOI substrate 8. 83. Then, a voltage is applied between the second substrate 3 and the active layer 83 of the SOI substrate 8 while heating the second substrate 3. This heating facilitates the movement of alkali metal positive ions of the second substrate 3, such as sodium ions (Na +). As a result, of the bonding surfaces between the second substrate 3 and the active layer 83, the bonding surface on the second substrate 3 side is negatively charged, and the bonding surface on the active layer 83 side is relatively charged positively. As a result, the second substrate 3 and the active layer 83 are firmly bonded by a covalent bond in which silicon (Si) and oxygen (O) share an electron pair.

[C] Production of first substrate 2 -C1-
Next, as shown in FIG. 9A, the base layer 81 is removed by etching or polishing.
As this etching method, for example, wet etching or dry etching can be used, but dry etching is preferably used. In any case, when the base layer 81 is removed, the insulating layer 82 serves as a stopper, but since dry etching does not use an etching solution, the active layer 83 facing the first electrode 33 is preferably damaged. Can be prevented. Thereby, the yield at the time of manufacture of the optical device 1 can be improved.

-C2-
Next, as shown in FIG. 9B, the insulating layer 82 is removed by etching.
As this etching method, for example, wet etching or dry etching can be used, but wet etching with an etchant containing hydrofluoric acid is preferably used. Thereby, the insulating layer 82 can be easily removed, and the surface of the active layer 83 exposed by the removal of the insulating layer 82 can be made extremely smooth.
In the above-described step B1, when a silicon substrate having an optimum thickness for performing the subsequent steps is used instead of the SOI substrate 8, the steps C1 and C1 are not performed. Also good. Thereby, the manufacturing process of the optical device 1 can be simplified.

-C3-
Next, as shown in FIG. 9C, the movable antireflection film 26 is formed on the upper surface of the active layer 83.
As a method of forming the movable antireflection film 26, the same method as the method of forming the fixed reflection film 35 described above can be used.

-C4-
Next, as shown in FIG. 9D, a resist layer 9 having openings corresponding to the openings 24 and 27 is formed.
As a method for forming the resist layer 9, the same method as in the steps A2 and A3 described above can be used.

-C5-
Next, the active layer 83 is etched by a dry etching method, particularly ICP etching through the resist layer 9 to form the opening 27 as shown in FIG. As shown, the opening 24 is formed. Thereby, the movable part 21, the support part 22, and the connection part 23 are formed.

  More specifically, when the active layer 83 is dry-etched via the resist layer 9, the etching rate in each opening region of the opening 24 is slower than the etching rate in the opening 27 due to the microloading effect. As shown in FIG. 9E, the formation of the opening 27 is completed before the opening 24 is formed. At this time, since the opening 27 is formed above the third recess 37 communicating with the first recess 31 via the groove 36, the space between the active layer 83 and the second substrate 3 is exposed to the outside. The pressure difference between the space and the outside is released.

Here, the microloading effect is a phenomenon in which the etching rate decreases as the opening size decreases. Therefore, the opening 27 has a dimension such that the etching rate is higher than the etching rate in each opening region of the opening 24. In the present embodiment, as shown in FIG. 1, the shape of the opening portion 27 is a square shape having a width that is wider than the opening width in the short direction of each opening region of the opening portion 24. The size and shape of the opening 27 are not limited to those described above as long as the etching rate at the opening 27 is higher than the etching rate at each opening region of the opening 24. A configuration can be employed.
When the microloading effect is used in this way, the opening 24 and the opening 27 can be formed while the opening 24 and the opening 27 are formed by the same etching process without separately providing an etching process for forming the opening 27. These can be formed in the order of 24, and the manufacturing process can be simplified.

When the dry etching is continued after the opening 27 is formed, the opening 24 is formed through as shown in FIG. 9F, and the formation of the movable portion 21, the support portion 22, and the connecting portion 23 is completed. To do.
At this time, as described above, before forming the movable portion 21 in the active layer 83 (that is, before forming the opening 24), the space between the active layer 83 and the second substrate 3 and the external Therefore, it is possible to prevent the connecting portion 23 from being damaged along with the formation of the opening 24.

In particular, in this step, ICP etching is performed. That is, the movable portion 21 is formed by alternately and repeatedly performing etching with an etching gas and formation of a protective film with a deposition gas.
Examples of the etching gas include SF _{6 and the} like, and examples of the deposition gas include C ₄ F _{8 and the} like.

In this step, the anisotropic etching is performed using the dry etching technique for the following reason.
When the wet etching technique is used, the etching solution enters between the active layer 83 and the second substrate 3 through the holes formed in the active layer 83 as the etching progresses, and the first electrode 33 and the insulating film 34. May be removed. On the other hand, when dry etching technology is used, there is no such danger.

In addition, when isotropic etching is used, the active layer 83 is isotropically etched and side etching occurs. In particular, when side etching occurs with respect to the connecting portion 23, the strength of the connecting portion 23 becomes weak, and the durability deteriorates. On the other hand, when anisotropic etching is used, side etching does not occur. Therefore, the etching dimension is excellent, and the side surface of the connecting portion 23 is also formed perpendicular to the plate surface of the active layer 83. The strength of the connecting portion 23 can be improved.
In the present invention, in this step, the movable portion 21, the support portion 22, and the connecting portion 23 may be formed using a dry etching method different from the above, and the movable portion 21 may be moved using a method other than the dry etching method. You may form the part 21, the support part 22, and the connection part 23. FIG.
-C6-
Thereafter, the resist layer 9 is removed to obtain a structure formed by bonding the first substrate 2 and the second substrate 3 as shown in FIG.

[D] Step of manufacturing third substrate 4 -D1-
First, as a substrate for forming the third substrate 4, a substrate 4a having optical transparency is prepared as shown in FIG.
As the substrate 4a, as in the substrate 3a described above, a substrate having a uniform thickness and free from deflection and scratches is preferably used. As the constituent material of the substrate 4a, the materials described in the description of the second substrate 3 can be used in the same manner as the constituent material of the substrate 3a.

-D2-
Next, using the same method as A1 to A4 in the above-described step [A], as shown in FIG. 10B, the recess 41 and the openings 47a and 47b are formed.
-D3-
Next, using the same method as A7 to A10 in the above-described step [A], as shown in FIG. 10C, the second electrode 43, the insulating film 44, and the fixed antireflection films 42 and 49 are formed. Form.
As described above, the third substrate 4 can be manufactured.

[E] Step of Joining Third Substrate 4 to First Substrate 2 Next, using the same method as B3 of step [B] described above, the third step obtained in step [D] described above is performed. The board | substrate 4 and the 1st board | substrate 2 of the structure obtained by process [C] mentioned above are joined.
Thereby, as shown in FIG.10 (d), the optical device 1 is obtained.
The optical device 1 (wavelength tunable filter) as described above is used in the form shown in FIGS. 11 and 12, for example.

FIG. 11 is a diagram showing an embodiment of a tunable filter module of the present invention, and FIG. 12 is a diagram showing an embodiment of an optical spectrum analyzer of the present invention.
A wavelength tunable filter module 100 shown in FIG. 11 is installed in an optical transmission path of an optical network such as a wavelength division multiplexing (WDM) optical transmission system. Such a wavelength tunable filter module 100 includes the optical device 1 that is the wavelength tunable filter described above, the optical fiber 101 and the lens 102 that guide light to the optical device 1, and the light emitted from the optical device 1 to the outside. A lens 103 and an optical fiber 104 are provided.

In such a wavelength tunable filter module 100, light having a plurality of wavelengths is incident on the optical device 1 through the optical fiber 101 and the lens 102, and only light having a desired wavelength is extracted through the lens 103 and the optical fiber 104. Can do.
Such a wavelength tunable filter module 100 has excellent optical characteristics while reducing the driving voltage.

  An optical spectrum analyzer 200 shown in FIG. 12 is a device that measures the spectrum characteristics (relationship between wavelength and intensity) of the light to be measured. Such an optical spectrum analyzer 200 includes a light incident unit 201 into which measured light is incident, the optical device 1 described above, and an optical system 202 that guides the measured light incident on the light incident unit 201 to the optical device 1. The light receiving element 203 that receives the light emitted from the optical device 1, the optical system 204 that guides the light emitted from the optical device 1 to the light receiving element 203, the drive of the optical device 1, and the output of the light receiving element 203 The control unit 205 that obtains the spectrum characteristics based on the above and the display unit 206 that displays the calculation result of the control unit 205 are provided.

In such an optical spectrum analyzer 200, the light to be measured incident on the light incident portion 201 is incident on the optical device 1 via the optical system 202. Then, the light emitted from the optical device 1 is received by the light receiving element 203 via the optical system 204, and the intensity of the light is obtained by the control unit 205. At this time, the control unit 205 obtains the intensity of the light received by the light receiving element 203 while sequentially changing the interference condition of the optical device 1. Then, the control unit 205 causes the display unit 206 to display information about the light intensity at each wavelength (for example, a spectrum waveform).
Such an optical spectrum analyzer 200 has excellent optical characteristics while reducing the driving voltage.

As described above, the optical device, the wavelength tunable filter, the wavelength tunable filter module, and the optical spectrum analyzer of the present invention have been described based on the illustrated embodiment, but the present invention is not limited to this, and the configuration of each part is as follows. It can be replaced with any configuration having a similar function. In addition, any other component may be added to the present invention.
Further, by using the optical device 1 described above, a wavelength tunable light source or a wavelength tunable laser can be realized.
In the above-described embodiment, the first gap G1 and the second gap G2 are formed by the first recess 31, but the second substrate 3 and the first substrate are not formed without forming the first recess 31. The first gap G1 and the second gap G2 may be formed by providing a spacer between the first gap G2 and the second gap G2.

  DESCRIPTION OF SYMBOLS 1 ... Optical device (wavelength variable filter) 2 ... 1st board | substrate 10 ... Current-carrying circuit 11 ... Power supply part 12 ... Detection part 13 ... Switching part 14 ... Control part 21 ... Movable part 22 ... Support portion 23... Connection portion 24... Opening portion 25... Movable reflection film 26... Movable antireflection film 27, 27 a, 27 b .. Opening portion 3 ... Second substrate 31. ... second recess 33, 33a, 33b ... first electrode 34 ... insulating film 35 ... fixed reflective film 36, 36a, 36b ... groove 37, 37a, 37b ... third recess 38, 38a, 38b …… Extraction electrode 39 …… Fixed antireflection film 4 …… Third substrate 41 …… Recess 43, 43a, 43b …… Second electrode 44 …… Insulating film 42, 49 …… Fixed antireflection film 47a, 47b ...... Openings 3a, 4a ... Substrate (second substrate) 5, 6, 6A ... Mask layer 51 ... Opening 7 ... Conductive layer 8 ... SOI substrate 81 ... Base layer 82 ... Insulating layer 83 ... Active layer (first layer) Substrate) 9: Resist layer 100: Wavelength tunable filter module 101, 104: Optical fiber 102, 103: Lens 200: Optical spectrum analyzer 201: Light incident section 202, 204: Optical system 203: Light reception Element 205 ... Control unit 206 ... Display unit G1 ... First gap G2 ... Second gap G3 ... Third gap L ... Light

Claims (19)

A fixed portion having a first light reflecting portion;
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. An optical device characterized by that. The optical device according to claim 1 , wherein each of the first electrode and the second electrode includes a plurality of electrodes. The number of electrodes constituting the first electrode is the same as the number of electrodes constituting the second electrode, and each electrode of the first electrode and each electrode of the second electrode form a pair. The optical device according to claim 2 . The shape of the first electrode, the optical device according to any one of claims 1 to 3 in the form and shape similar to the second electrode. The optical device according to claim 4 , wherein a size of the first electrode is the same as a size of the second electrode. A support portion for supporting the movable portion; and a connecting portion for connecting the movable portion and the support portion so that the movable portion can be displaced with respect to the support portion. the optical device according to any of the support portion and the connecting portion claims 1 are formed integrally with 5. A first substrate on which the movable portion, the support portion, and the connecting portion are formed; a second substrate that is fixedly provided to the support portion on one surface side of the first substrate; A third substrate fixed to the support portion on the other surface side of the first substrate, and each of the first substrate, the second substrate, and the third substrate. Is formed with an airtight space so as to allow displacement of the movable part, and the first electrode and the first light reflecting part are provided on the second substrate, The optical device according to claim 6 , wherein the second electrode is provided on the third substrate. A concave portion is formed on a surface of the second substrate on the first substrate side, and the first light reflecting portion and the first electrode are provided on a bottom surface of the concave portion. Item 8. The optical device according to Item 7 . The concave portion includes a first concave portion and a second concave portion formed on a bottom surface of the first concave portion, and the first electrode is formed on the outer side of the second concave portion. The optical device according to claim 8 , wherein the first light reflecting portion is provided on a bottom surface of the second recess. The optical device according to claim 9 , wherein the first electrode is provided so as to surround the first light reflecting portion. The optical device according to any one of the first substrate, the silicon to claims 7 as a main material 10. The optical device according to claim 11 , wherein at least one of the second substrate and the third substrate is made of glass as a main material. The optical device according to claim 12 , wherein at least one of the second substrate and the third substrate is made of glass containing alkali metal ions as a main material. Said first substrate, an optical device according to any one of claims 7 to 13 is one formed by processing one of the Si layer of the SOI wafer. The first at least one of the light reflecting portion and the second light reflecting portion, an optical device according to any one of claims 1 to 14 is composed of a dielectric multilayer film. In a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode, the first electrode and the second electrode are: the optical device according to any one of claims 1 is provided symmetrically through the movable portion 15. A fixed portion having a first light reflecting portion;
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. A tunable filter characterized by that. A fixed portion having a first light reflecting portion;
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. A tunable filter module characterized by the above. A fixed portion having a first light reflecting portion;
A movable portion having a second light reflecting portion opposed to the first light reflecting portion with a first gap therebetween and displaceable with respect to the fixed portion so as to change the first gap;
A first electrode fixedly provided on the fixed portion so as to face the surface of the movable portion on the first light reflecting portion side with a second gap therebetween, and has a substantially annular shape as a whole; ,
A second portion that is fixedly provided to the fixed portion so as to face the surface of the movable portion opposite to the first light reflecting portion with a third gap therebetween, and has a substantially annular shape as a whole. Electrodes,
An energization circuit connected to each of the first electrode and the second electrode,
One of the first electrode and the second electrode functions as a detection electrode for detecting a capacitance between the first electrode and the second electrode, and the other electrode is connected to the movable unit. By causing a potential difference between them, an electrostatic attractive force is generated between them, and functions as a drive electrode for changing the position and / or posture of the movable part,
It is configured to repeat light reflection between the first light reflection part and the second light reflection part to cause interference, and to emit light having a wavelength according to the distance between them. ,
The energization circuit is configured to be switched alternately between when the first electrode and the second electrode function as the detection electrode and when they function as the drive electrode,
Based on the electrostatic capacitance between the movable part and the second electrode, by applying a voltage between the movable part and the first electrode, the movable part is moved to the first electrode side. Can be displaced,
Based on the electrostatic capacitance between the movable part and the first electrode, by applying a voltage between the movable part and the second electrode, the movable part is moved to the second electrode side. Can be displaced,
The second gap and the third gap are equal in a state where no potential difference is generated between the movable part and the first electrode and between the movable part and the second electrode. An optical spectrum analyzer characterized by this.

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