JPH0736350Y2 - Optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) This invention is directed to an operating characteristic of a waveguide type optical switch formed by using, for example, a ferroelectric crystal substrate, due to an electric charge generated due to a pyroelectric effect. The present invention relates to an optical device configured to prevent the fluctuation of

(Prior Art) It is known that in an optical device formed using a ferroelectric crystal such as LiNbO ₃ , the operating characteristics, for example, the operating point of an optical switch fluctuates due to the pyroelectric effect. As an optical device for preventing such characteristic fluctuation, for example, there is one disclosed in Document I: JP-A-62-173428. The conventional optical device of Document I will be briefly described below with reference to the drawings.

FIG. 8 is a cross-sectional view schematically showing a main part configuration of an embodiment of a conventional optical device. One waveguide of an optical switch having two waveguides forming an X branch and the vicinity thereof are shown. The configuration is shown schematically.

In the optical device shown in the figure, a Ti diffusion waveguide 12 is provided on one side of a z-cut LiNbO ₃ substrate 10, and SiO ₂ is formed on the waveguide 12.
A buffer layer 14, a control electrode 16 for controlling the refractive index of the waveguide, and a Si film body 18 are sequentially provided, and a grounding conductive film body 20 is provided on the other side of the substrate 10. The control electrode 16 is composed of Al electrode members 16a to 16c, and when an electric field is applied to the waveguide via the control electrode 16, the refractive index of the waveguide changes according to this electric field. The film body 12 includes at least electrode members 16a, 16b, 16c.
It has a resistance value such that a large current which is provided between the control electrodes 16 does not flow between the control electrodes 16 and destroys the device when the refractive index of the waveguide is controlled.

Since the film body 12 is provided at least between the electrode members 16a, 16b, 16c, when + charge is generated on the substrate surface 10a on one side of the substrate 10 due to the pyroelectric effect, as shown in FIG. Negative charges corresponding to positive charges are uniformly generated in the control electrode 16 and the film body 18 along the substrate surface 10a. As a result, it is possible to eliminate fluctuations in operating characteristics due to the pyroelectric effect.

In addition to this, the grounding conductive film body 20 is grounded during the operation of the optical device, and therefore, it is possible to prevent the electric charge from accumulating on the substrate surface 10b on the other side of the substrate 10 due to the boosting effect. As a result,
It is possible to prevent the generation of an electric field between the substrate surfaces 10a and 10b, so that it is possible to eliminate fluctuations in the operating characteristics of the optical device due to the pyroelectric effect.

(Problems to be solved by the invention) However, in the optical device as described above, in order to prevent the propagation light of the waveguide 12 from being absorbed by the control electrode 16 and causing a loss of light, the buffer layer 14 is usually provided. Control electrode through
16 is provided on the waveguide 12 so that the waveguide 12 and the control electrode 16 do not come into direct contact with each other. The impurity carriers contained in the buffer layer 14 act so as to cancel the electric field formed by the control electrode 16 for controlling the refractive index, and as a result, there is a problem in that the operating characteristics fluctuate, particularly in the optical switch. It was

An object of the present invention is to solve the above-mentioned conventional problems and provide an optical device having more stable operation characteristics than ever before.

(Means for Solving the Problems) In order to achieve this object, the optical device of the present invention is
In an optical device comprising a waveguide provided on a substrate having a pyroelectric effect, a control electrode provided on the substrate for controlling the refractive index of the waveguide, and a film body provided at least between the control electrodes. A gap is provided between the film surface and the substrate surface on the side where the waveguide is provided.

(Operation) According to the above-mentioned configuration, since the gap is provided between the substrate surface on the side where the waveguide is provided and the film body, it is possible to prevent the light propagating through the waveguide from being absorbed by the control electrode. .

Embodiment An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the drawings are only schematically illustrated to the extent that the present invention can be understood, and therefore, the shapes, dimensions, and disposition positions of each component are not limited to the illustrated examples.

First Embodiment FIGS. 1 and 2 are a sectional view and a plan view schematically showing the constitution of the first embodiment of the present invention, and FIG. 1 is a line I- of FIG.
A cross section taken along line I is shown.

As shown in these figures, the optical device 20 of the first embodiment
Are waveguides 24 and 26 provided on the substrate 22 having a pyroelectric effect,
A control electrode 28 provided on the substrate 22 for controlling the refractive index of the waveguides 24 and 26, and a film body 30 provided at least between the control electrodes 28.
And a gap 32 is provided between the film body 30 and the substrate surface 22a on the side where the waveguides 24 and 26 are provided.

The optical device 20 of this embodiment includes the control electrode 28 and the film body.
It has a configuration including a support portion 34 for supporting the 30.

Incidentally, reference numeral 36 in the drawing denotes an etching solution injecting part used when the optical device 20 is produced.

Hereinafter, this embodiment will be described in more detail.

The first embodiment is an example in which the present invention is applied to a directional coupler type waveguide type optical switch.

In this example, waveguides 24 and 26 that are parallel to each other are provided on one substrate surface 22a side of the substrate 22.

The control electrode 28 is composed of two electrode members 28a and 28b provided for the waveguides 24 and 26, and the supporting portion 34 is composed of a reinforcing member 34a and a spacer 34b. In order to support the control electrode 28 on the void 32, the spacer 34b surrounds the void 32 so as to surround the substrate 22a.
The film body 30, the control electrode 28, and the reinforcing member 34a are sequentially provided on the spacer 34b. The film body 30 and the control electrode 28 on the void 32 are supported by the reinforcing member 34a. Optical device 2
0 is a use environment atmosphere, for example, air or an inert gas is a void 32
Operates in a full state.

The film body 30 is placed at least between the control electrodes 28 (electrode members 28a, 28b
However, in this example, the film body 30 is provided in a region corresponding to almost the entire substrate surface 22a. By providing the film body 30 at least between the control electrodes 28, + charges correspond to + charges when they are generated on the substrate surface 22a by the pyroelectric effect.
The charge is distributed almost uniformly along the substrate surface 22a and the control electrode 2
8 and the film body 30 can be prevented from changing the operating characteristics due to the pyroelectric effect.

Next, with reference to FIG. 3, an example of a method for producing the optical device 20 of the first embodiment will be described. FIG. 3 is a process diagram schematically showing main manufacturing process steps of the first embodiment, and FIGS. 3A to 3C are plan views corresponding to FIG. 2 and FIGS. G) is a sectional view corresponding to FIG. 1.

First, a z-cut LiNbO ₃ substrate is prepared as the substrate 22 having the pyroelectric effect, and linear waveguides 24 and 26 are formed on the substrate surface 22a side of the substrate 22 by using a diffusion technique (FIG. 3 (A)).

Then SiO ₂ , Si, Cr or any other suitable spacer 34b
Is laminated on the substrate surface 22a, and then the layer of this forming material is patterned so as to expose the substrate surface 22a in the region where the void 32 is to be formed to form the spacer 34b (FIG. 3 (B)). ).

Next, a buried layer 40 that is dissolved and removed by an etching solution in a step described below is stacked on the exposed substrate surface 22a, and the region where the void 32 is to be formed is buried with the buried layer 40.
(FIG. 3 (C)). As a material for forming the buried layer 40, any suitable material that can be removed by etching, such as resist or SiO ₂ , is used. Preferably, the material for forming the buried layer 40 is selected so that the buried layer 40 is etched away, but the constituent components of the optical device 20 other than the buried layer 40 are not etched away.

Next, the film body 30 is laminated on the embedding layer 40 (FIG. 3 (E)). As the material for forming the film body 30, electrode members 28a, 2
Any suitable dielectric material that can form a film body 30 having a resistance value so that a large current flows between the members 28a and 28b when the device 8b is energized and the device 20 is not destroyed is used. For example annealed
The Si layer or the cermet layer can be the film body 30.

Next, a layer of any suitable electrode material is formed on the film body 30, and this layer is patterned to form electrode members 28a and 28b (FIG. 3 (E)).

Then, a reinforcing member 34a made of polyimide or any other suitable material is laminated on the electrode members 28a and 28b (FIG. 3 (F)).

Next, the etching liquid injection part 36, for example, a hole having a depth from the surface of the reinforcing member 34a to the embedded layer 40 is formed by etching the reinforcing member 34a and the film body 30 (FIG. 3 (G)).

Next, the etchant for the embedding layer 40 is injected into the etchant injecting portion 36, and the melted embedding layer 40 is discharged from the etching injecting port 36 to form the void 32, and the optical device 20 shown in FIG.
To get Although the buried layer 40 is dissolved in the etching liquid for the buried layer 40, the optical device 20 such as the support portion 34, the film body 30, the substrate 22 or the like is used.
Any suitable solvent that does not substantially dissolve the constituents of is used, for example, a solvent of acetone or a solvent of HF.

Second Embodiment FIGS. 4 and 5 are a sectional view and a plan view schematically showing the configuration of the second embodiment of the present invention, and FIG. 4 is an IV of FIG.
-Shows a cross section taken along line IV. The constituents corresponding to those of the first embodiment are designated by the same reference numerals.

Hereinafter, differences from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

The optical device 42 of the second embodiment is an example in which the present invention is applied to a waveguide type optical switch of branch interference type.
Of the linear waveguides 24 and 26 and the Y-branch waveguide 4 on the substrate surface 22a side of
A branch interferometer consisting of 4 and 46 is provided. The Y branch waveguide 44 is provided on one side of the straight waveguides 24 and 26, and the straight waveguide 24 is coupled to one of the two branch ends of the straight waveguide 24 and the straight waveguide 26 is coupled to the other. Similarly, the Y branch waveguide 46 is provided on the other side of the straight waveguides 24 and 26, and the straight waveguide 24 is coupled to one of the two branches of the straight waveguide 46 and the straight waveguide 26 is coupled to the other branch, Configure an interferometer.

The optical device 42 of the second embodiment can also be manufactured in the same manner as in the first embodiment.

Third Embodiment FIGS. 6 and 7 are a sectional view and a plan view for explaining a third embodiment of the present invention, and FIG. 6 is a sectional view taken along line VI-VI in FIG. Show. The constituents corresponding to the constituents of the above-described embodiment are designated by the same reference numerals.

An optical device 48 of the third embodiment is an example in which the present invention is applied to a directional coupler type waveguide type optical switch as in the first embodiment. Hereinafter, differences from the first embodiment will be described, and detailed description of the same points as the first embodiment will be omitted.

In the first embodiment, voids 32 are also formed in the regions immediately below the electrode members 28a, 28b.
However, in this third embodiment, the void 32 is formed in the electrode member 28.
It is provided so as to be located between a and 28b, and is not provided in the region immediately below the electrode members 28a and 28b.

In the first embodiment, the etchant injection portion 36 is a hole, but in the third embodiment, the device end face a on one end side of the waveguides 24, 26 to the other end side of the waveguides 24, 26 is used. A slit-shaped groove extending to the device end surface b is formed, and a void 32 extending from the end surface a to b is formed.

The optical device 48 of the third embodiment can also be manufactured in the same manner as in the first embodiment.

The present invention is not limited to the above-described embodiments, and therefore, the shape, forming material, forming method, forming procedure, arrangement position, arrangement number and size of each component can be arbitrarily changed.

For example, a grounding conductive film may be provided on the substrate surface of the substrate 22 opposite to the substrate surface 22a, as in the conventional case.

The present invention can be applied to optical switches and other optical devices.

(Effect of the Invention) As is apparent from the above description, according to the optical device of the present invention, since the gap is provided between the substrate surface on the side where the waveguide is provided and the film body, the waveguide is propagated. The absorbed light can be prevented from being absorbed by the control electrode. Since the voids do not contain impurity carriers, fluctuations in the operating characteristics of the optical device, particularly fluctuations in the operating point, are not caused by the impurity carriers.

Further, since the film body is provided at least between the electrodes, it is possible to prevent the fluctuation of the operating characteristics of the optical device due to the pyroelectric effect.

Therefore, according to the present invention, it is possible to provide an optical device with less variation in operating characteristics than ever before.

[Brief description of drawings]

1 and 2 are a sectional view and a plan view schematically showing the constitution of the first embodiment of the present invention, and FIGS. 3 (A) to (G) show the main part of an example of the production method of the first embodiment. FIGS. 4 and 5 are sectional views and plan views schematically showing the construction of a second embodiment of the present invention, and FIGS. 6 and 7 are third embodiments of the present invention. FIG. 8 is a cross-sectional view and a plan view schematically showing the configuration of an example, and FIG. 8 is a main-portion cross-sectional view schematically showing the configuration of a conventional optical device. 20, 42, 48 …… Optical device 22 …… Substrate, 24, 26 …… Waveguide 28 …… Control electrode, 30 …… Membrane 32 …… Void, 34 …… Support.

Claims (2)

[Scope of utility model registration request] 1. A waveguide provided on a substrate having a pyroelectric effect,
In an optical device comprising a control electrode provided on the substrate for controlling the refractive index of the waveguide and a film body provided at least between the control electrodes, the substrate surface on the side where the waveguide is provided An optical device characterized in that an air gap is provided between the film body and the film body. 2. The optical device according to claim 1, further comprising a support portion for supporting the control electrode and the film body.