JP2005148653A - Reflectivity variable mirror, light power attenuator, and driving method for light power attenuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflectivity variable mirror which has a simple structure and in which reflectivity is electrically adjustable, and a light power attenuator using it. <P>SOLUTION: A reflectivity variable mirror consists of a laminated membrane 13 including thin films 19 and 23 having refractive indexes that differ according to a plurality of different conditions, respectively. The reflectivity variable mirror has a structure in which the conditions of the thin films 19 and 23 are controlled, the reflectivity of the laminated membrane 13 is changed, and the reflection energy of the light irradiated onto the laminated membrane 13 is adjusted. By using this reflectivity variable mirror, a light power attenuator is constituted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a reflectivity variable mirror and a driving method thereof.
The present invention relates to a device for adjusting the amount of light, a so-called optical power attenuator, and in particular, an optical power attenuator using a variable reflectivity mirror, an optical power attenuator using a multi-array variable reflectivity mirror, and an optical power attenuator. The present invention relates to a driving method.

  Conventionally, communication using an optical fiber, which has been mostly used for a trunk line connecting countries, has become popular not only for the trunk line but also for general households in recent years. With the progress of laying of optical fibers, not only high performance of each component used for optical communication including a single optical fiber is required, but also cost reduction is required. Furthermore, for the purpose of increasing the transfer rate of the entire optical communication system, the number of relay points for replacing optical signals with electrical signals is reduced, and optical paths can be switched and branched using optical switches and optical distributors. Has begun.

  Furthermore, in recent years, in order to increase the amount of information transmitted to optical fibers, many attempts have been made on wavelength division multiplexing (WDM, CWDM, DWDM) in which optical signals of different wavelengths are propagated to one optical fiber using the orthogonality of light. Has been made.

  In order to transmit a large amount of information to a single optical fiber over a long distance, it is desirable to improve the quality of the optical signal before entering the optical fiber. That is, it is desirable to make the intensity of light incident on the optical fiber uniform, not only in the case of a wavelength division multiplexing transmission system. The amount of light energy changes as it passes through optical components such as an optical switch and an optical distributor. In order to make the intensity of light incident on the optical fiber uniform, the amount of light is adjusted by an optical amplifier and an optical attenuator.

  FIG. 17 shows a configuration example of the optical attenuator. The optical attenuator 1 is a configuration example in which the amount of light is adjusted by inputting an electric signal. In the optical attenuator 1, the optical waveguides 2 and 3 branched between the incident portion and the outgoing portion of the light 6 are formed on the main surface of the substrate 5, and a heater is disposed above the one branched optical waveguide 2. The temperature of one of the optical waveguides 2 rises due to the heating of the heater 4, that is, the input of an electric signal, and its refractive index changes, and the phase of the branched light differs depending on the change in the refractive index of this optical waveguide 2. Thus, the energy of the combined light of the light guided through the two optical waveguides 2 and 3 is reduced.

Patent Document 1 describes an optical phase modulator that performs stable optical phase modulation without being limited by the polarization state of incident light.
Patent Document 2 describes a waveguide type optical device that can achieve a relatively low driving voltage, a low microwave attenuation, and a wide bandwidth.
Japanese Patent Laid-Open No. 9-243976 JP-A-9-304745

  By the way, the operation characteristics of the optical attenuator 1 using the optical waveguides 2 and 3 are such that the output is obtained when the phase difference between the light guided through the two optical waveguides 2 and 3 becomes λ / 2 by heating by the heater 4. When the heater 4 is not heated, that is, when there is no phase change, the input light is output as it is, and adjustment from 0 to 100% should be possible. However, in reality, since there is an input loss to the optical waveguides 2 and 3 and a waveguide loss of the optical waveguides 2 and 3, it is necessary to use an optical amplifier in combination. Furthermore, since the branched optical waveguides 2 and 3 can be formed only on the main surface of the substrate 5, they can be arranged in one dimension, but cannot be arranged in two dimensions. In addition, the manufacturing process of the optical waveguides 2 and 3 itself includes many complicated diffusion processes or polishing processes, and there is a problem that cost reduction is not easy.

In view of the above-described points, the present invention provides a reflectivity variable mirror that can be applied to an optical attenuator, has a simple configuration, and whose reflectivity can be adjusted electrically, and a driving method thereof. As a driving method, the present invention provides a driving method that is effective for adapting to the usage environment, long-term life countermeasures and failure countermeasures.
The present invention also provides an optical power attenuator that can be manufactured by an easy method using the reflectance adjusting mirror, and an optical power attenuator that enables a plurality of arrangements of the reflectance variable mirror.
The present invention also provides a method for driving an optical power attenuator that is effective for adaptation to the use environment, long-term service life countermeasures, failure countermeasures, and the like.

The variable reflectivity mirror according to the present invention includes a laminated film including a thin film having different refractive indexes in each of a plurality of different states, and controls the state of the thin film to change the reflectance of the laminated film to irradiate the laminated film. The reflection energy of the emitted light is adjusted.
The thin film constituting the laminated film is preferably formed of a phase change material. In this case, the reflectance of the laminated film can be adjusted by adjusting the thermal energy supplied to the thin film of the laminated film.
The laminated film has a heat generating function for generating heat from the thin film. A conductive film can be formed on both sides of the thin film constituting the laminated film.

In the reflectivity variable mirror of the present invention, by controlling the state of the thin film constituting the laminated film, the refractive index of the thin film is controlled to change the light reflectance of the laminated film. Thereby, the reflected energy of the light irradiated to the laminated film is adjusted.
When the thin film is formed of a phase change material, the light reflectivity of the laminated film can be adjusted by first bringing the phase change material into an amorphous state according to the processing temperature and then changing it to another crystalline state. When it has a heat generating function for generating heat from the thin film, it is possible to adjust the light reflectivity of the laminated film by controlling the state of the thin film by heat generation. Furthermore, when forming a conductive film on both sides of the thin film, a current is passed through the conductive film to cause the heater film as a heat generating function to generate heat, and the state of the thin film can be controlled by this heat generation. It is possible to adjust the light reflectance.

An optical power attenuator according to the present invention comprises a laminated film including a thin film having different refractive indexes in each of a plurality of different states, changes the reflectance of the laminated film by controlling the state of the thin film, and is irradiated to the laminated film. A variable reflectivity mirror that adjusts the reflected energy of the reflected light is disposed in the optical path, and is configured to adjust the amount of light reflected by the optical path.
An optical power attenuator according to the present invention comprises a laminated film including a thin film having a different refractive index in each of a plurality of different states, changes the reflectance of the laminated film by controlling the state of the thin film, and irradiates the laminated film A plurality of variable reflectivity mirrors for adjusting the reflected energy of the reflected light are formed on one substrate, and each reflectivity variable mirror is disposed in each of the plurality of optical paths, and the amount of light reflected by each optical path is determined. Each is configured to be adjusted.
The thin film constituting the laminated film is preferably formed of a phase change material. In this case, the reflectance and transmittance of the multilayer film can be changed by adjusting the thermal energy supplied to the thin film of the multilayer film.
The laminated film has a heat generating function for generating heat from the thin film. A conductive film can be formed on both sides of the thin film constituting the laminated film.

In the optical power attenuator of the present invention, since the variable reflectivity mirror is disposed in the optical path, the amount of light reflected in the optical path is adjusted. In the optical power attenuator of the present invention, a plurality of the above-described reflectivity variable mirrors are formed on one substrate, and this so-called multi-array reflectivity variable mirror corresponds to each reflectivity variable mirror in each optical path. By arranging in this manner, the amount of light reflected in each optical path is adjusted.
When forming a thin film with a phase change material, the light reflectivity of the laminated film is adjusted by making the phase change material into an amorphous state after the processing temperature and then changing to another crystalline state, and the amount of reflected light in the optical path is reduced. Adjustment is possible. When the thin film has a heat generating function for generating heat, the state of the thin film is controlled by heat generation, the light reflectance of the laminated film is adjusted, and the amount of reflected light in the optical path can be adjusted. Further, when the conductive film is formed on both sides of the thin film, the light reflectance of the laminated film is electrically adjusted as described above, and the amount of reflected light in the optical path can be adjusted electrically.

The driving method of the reflectivity variable mirror according to the present invention includes a laminated film including a thin film having different refractive indexes in each of a plurality of different states, and the reflectance of the laminated film is changed by controlling the state of the thin film. The variable reflectivity mirror is driven while the state of the thin film is electrically monitored with respect to the reflectivity variable mirror that adjusts the reflection energy of the light applied to the film.
The thin film constituting the laminated film of the reflectivity variable mirror is preferably formed of a phase change material. Adjustment of the reflectivity of the laminated film can be achieved by once returning the phase change material to an amorphous state and then changing to another crystalline state.
As a method of electrically monitoring the state of the thin film constituting the laminated film, a method of monitoring the capacitance can be employed.
The state of the thin film constituting the laminated film can be electrically monitored to inspect the state of the reflectivity variable mirror. The state of the thin film can be electrically monitored, and the amount of light reflected by the reflectivity variable mirror can be adjusted.

In the method of driving the variable reflectivity mirror according to the present invention, the state of the thin film constituting the laminated film is electrically monitored, so that the switching of the state of the thin film can be monitored, and operation reliability can be obtained. When the thin film is formed of a phase change material, the switching of the state of the thin film is performed after the amorphous state is changed, so that the operation stability is improved.
When monitoring the state of the thin film with capacitance, stable monitoring can be performed. When the thin film state is electrically monitored to inspect the light quantity (reflected light quantity) of the variable reflectivity mirror, or when the reflected light quantity of the variable reflectivity mirror is adjusted, operational reliability can be obtained.

An optical power attenuator driving method according to the present invention includes a laminated film including thin films having different refractive indexes in a plurality of different states, and changes the reflectance of the laminated film by controlling the state of the thin film. A variable reflectivity mirror that adjusts the reflected energy of the light irradiated on the optical path is arranged in the optical path, and the optical power attenuator that adjusts the amount of light reflected by the optical path is monitored while the thin film is electrically monitored. Drive the power attenuator.
The thin film constituting the reflectivity variable mirror is preferably formed of a phase change material. The output adjustment of the optical power attenuator can be brought into another crystalline state after the phase change material is once returned to the amorphous state.
As a method for electrically monitoring the state of the thin film constituting the laminated film, a method for monitoring the capacitance can be employed.
The state of the optical power attenuator can be inspected by electrically monitoring the state of the thin film constituting the laminated film. The state of the thin film can be electrically monitored to adjust the light amount of the optical power attenuator.

In the optical power attenuator driving method of the present invention, the reflectivity variable mirror is disposed in the optical path, and the optical power attenuator is driven by electrically monitoring the thin film constituting the laminated film of the reflectivity variable mirror. The amount of light by the reflectivity variable mirror can be adjusted appropriately.
When the thin film is formed of a phase change material, the switching of the thin film state is performed after the amorphous state is changed, so that the operation stability of the optical power attenuator is increased. When monitoring the state of the thin film with capacitance, stable operation of the optical power attenuator can be monitored. When the state of the thin film is electrically monitored to inspect the amount of light of the optical power attenuator, or when the amount of light of the optical power attenuator is adjusted, operational reliability can be obtained.

  According to the reflectivity variable mirror according to the present invention, the configuration can be simplified. Multiple reflection mirrors can be easily made. By forming the thin film constituting the laminated film with a phase change material, the optical state of the phase change material can be electrically monitored, and the reflectivity of the reflectivity variable mirror can be adjusted electrically.

  According to the optical power attenuator according to the present invention, since the reflectivity variable mirror is used, the configuration can be simplified and it can be manufactured by an easy method. Multiple optical power attenuators can be easily made. By forming the thin film constituting the laminated film from the phase change material, the optical state of the phase change material can be electrically monitored, and the light amount of the optical power attenuator can be adjusted electrically.

  According to the driving method of the reflectivity variable mirror according to the present invention, the state of the thin film can be monitored by electrically monitoring the state of the thin film, and the operation reliability can be improved. When a thin film is formed of a phase change material, the value obtained by electrically monitoring the state of the thin film can be used, and input when switching the state of the thin film according to changes in the external environment and changes in material properties due to long-term use. The signal can be adjusted. At the time of switching, since the switching is performed after the amorphous state is once set, the stability of the operation can be improved.

  According to the method for driving an optical power attenuator according to the present invention, the state of the thin film constituting the laminated film of the reflectivity variable mirror can be electrically monitored, so that the switching of the state of the thin film can be monitored. The reliability of the operation of the power attenuator can be increased. When a thin film is formed of a phase change material, the value obtained by electrically monitoring the state of the thin film can be used, and input when switching the state of the thin film according to changes in the external environment and changes in material properties due to long-term use. The signal can be adjusted. At the time of switching, since the switching is performed after the amorphous state is once set, the stability of the operation can be improved.

  Hereinafter, a reflectivity variable mirror with adjustable reflectivity according to the present invention and a driving method thereof, an optical power attenuator using the reflectivity variable mirror, and a drive method thereof will be described with reference to the drawings.

  First, the phase change material used for the reflectivity variable mirror of the present invention will be described. 1 and 2 show the measurement results of n and k in the wavelength range from 350 nm to 1700 nm when the refractive index of the phase change material (material film) made of Ge2 Sb2 Te5 is n-ik. As parameters in FIGS. 1 and 2, there are five conditions of a crystal state and an amorphous state with different crystallization temperatures (175 ° C., 250 ° C., 325 ° C., 400 ° C.). This phase change material composed of Ge2 Sb2 Te5 is a material that can take a plurality of states such as a crystallized state and an amorphous state depending on a difference in heat treatment temperature and a cooling rate after heating, and is also used as a recording material of an optical disc apparatus. Material.

In FIGS. 1 and 2, the ● marks are n and k in an amorphous state, the ▲ marks are n and k in a crystallization state at 175 ° C., the □ marks are n and k in a crystallization state at 250 ° C., and the ▲ mark is 325 ° C. N, k, and ♦ indicate n, k in the crystallized state at 400 ° C.
From the results shown in FIGS. 1 and 2, it is recognized that the phase change material has a difference in optical constant due to a difference in crystallization temperature in addition to a difference in optical constant due to a difference between an amorphous state and a crystallization state. . More specific numerical values include refractive indexes n (175), n (250), n () in a crystallization state at a crystallization temperature of 175 ° C., 250 ° C., 325 ° C., and 400 ° C. with respect to a wavelength of 1550 nm. 325), n (400), and the refractive index n (amo) in the amorphous state are n (175) = 8.2755-4.7665i, n (250) = 8.296-3.894i, n (325), respectively. = 8.1844-3.1303i, n (400) = 8.1695-3.081i, and n (amo) = 5.6224-0.94610i.

The reflectivity variable mirror according to the present invention is configured by using a material film whose optical characteristics change, such as the phase change material shown in FIGS.
FIG. 3 shows a schematic configuration of an embodiment of the variable reflectivity mirror according to the present invention, and FIG. 4 shows an example of a film thickness configuration of the variable reflectivity mirror. In the reflectivity variable mirror 11 according to the present embodiment, a laminated film 13 whose optical characteristics are changed is formed on a transparent substrate, for example, a glass substrate 12, and a transparent substrate, for example, a glass substrate 14 is formed on the laminated film 13. Configured. The laminated film 13 whose optical characteristics change is composed of a laminated film including a thin film whose optical characteristics change depending on the processing conditions of the material, and the laminated film is formed so that the change in the optical characteristics of the thin film becomes a change in reflectance. Designed configuration. Therefore, the reflectivity variable mirror 11 is a mirror capable of adjusting the reflectivity by adjusting the processing conditions of the thin film material. A beam splitter 15 is disposed in the normal direction of the laminated film 13 in the reflectivity variable mirror 11.

  As shown in FIG. 4, for example, the laminated film 13 constituting the reflectivity variable mirror 11 with the changed optical characteristics has a silicon film (Si) 17 and a silicon nitride film (SiN) on a glass substrate 12. 18, a phase change material film (PC) 19 having optical changes shown in FIGS. 1 and 2, a silicon oxide film (SiO 2) 20, a silicon film (Si) 21, and a silicon oxide film (SiO 2) 22 1 and FIG. 2, a phase change material film (PC) 23 having an optical change, a silicon nitride film (SiN) 24, and a silicon film (Si) 25 are sequentially stacked, and further thereon. A glass substrate 14 is formed. As a specific example, the laminated film 13 includes a glass substrate (n = 1.5) 12, a 10 nm thick silicon film (n = 3.5) 17, a 270 nm thick silicon nitride film (n = 2.0) 18, 20 nm thick phase change material film 19, 100 nm thick silicon oxide film (n = 1.47) 20: para, 150 nm thick silicon film (n = 3.5) 21, 100 nm thick silicon oxide film (n = 1) 47) 22: para, 20 nm thick phase change material film 23, 270 thick silicon nitride film (n = 2.0) 24, 10 nm thick silicon film (n = 3.5) 25, glass substrate (n = 1.5) It is comprised by the laminated film which consists of 14. In FIG. 4, the film structure is symmetrical in the vertical direction, and both surfaces correspond to an attenuator (optical switch).

  A silicon oxide film (n = 1.47) 20 described as para in the film configuration of FIG. 4 so that the change in reflectivity of the reflectivity variable mirror 11 can be understood by the change in the optical characteristics of the phase change material. FIG. 5 shows a change in the reflectivity of the reflectivity variable mirror 11 when the film thicknesses of No. 22 and No. 22 are changed from 0 nm to 400 nm. The reflectance is the reflectance when the incident angle of the incident light Lin shown in FIG. 3 is in the normal direction of the laminated film 13. In FIG. 3, Lout is output light reflected from the laminated film 3 and output by being reflected by the beam splitter 15.

In FIG. 5, the mark ● represents the reflectance R in the amorphous state, the mark ▲ represents the reflectance r in the crystallization state at 175 ° C., the mark □ represents the reflectance R in the crystallization state at 250 ° C., and the mark ▼ represents the reflectance at 325 ° C. R and ♦ indicate the reflectance R in the crystallized state at 400 ° C.
From the results shown in FIG. 5, when the thickness of the silicon oxide films 20 and 22 is around 300 nm, the change in reflectance is not different between the amorphous state and the crystallized state, but the silicon oxide films 20 and 22 It can be seen that when the film thickness is about 100 nm, the reflectance varies greatly between the amorphous state and the crystallized state, and even in the crystallized state, the reflectance varies depending on the processing temperature.

  More specifically, the reflectances R (175), R (250), R (325), R (in the crystallization state at a crystallization temperature of 175 ° C., 250 ° C., 325 ° C., and 400 ° C. with respect to a wavelength of 1550 nm. 400) and amorphous state reflectance R (amo) are R (amo) = 0.2%, R (175) = 37.2%, R (250) = 31.3%, R (325), respectively. = 28.1% and R (400) = 27.8%, and it is recognized that the reflectance is adjusted by the difference in crystallization temperature. In this configuration example, the reflectivity is greatly different between the amorphous state and the crystallized state, and the reflectivity is 0.2% or less in the amorphous state. Compared with the state, the reflectance is extremely low.

  Next, a configuration for adjusting the reflectance of the reflectivity variable mirror 11 and a method for adjusting the reflectance will be described. FIG. 6 shows a configuration for adjusting the reflectivity of the reflectivity variable mirror 11. The variable reflectivity mirror 11 extends from the entire upper surface of the multilayer film 13 to both sides, including the phase change material film 23 whose optical characteristics change due to the difference in the processing conditions of the materials shown in FIG. A film (so-called heater film) 27 serving as a heater, and a heater extending on both sides of the laminated film 13. Conductive patterns 28A and 28B formed on the film 27, respectively. The heater film 27 is formed of, for example, a conductive material film having a thickness of about 10 nm, in this example, a silicon film. The conductor patterns 28A and 28B are formed of a low resistance film such as aluminum, for example, and are formed at positions where the optical spot 29 does not hit.

  A current is passed through the heater film 27 through the conductor patterns 28A and 28B through the variable reflectivity mirror 11. That is, the heater portion 27a is heated by current injection into the heater portion (heater film on the laminated film 13) 27a, which is an operation input of the electric signal, and the phase change material film 23 in the vicinity thereof is changed according to the input state of the electric signal. The reflectance of the reflectivity variable mirror 11 is adjusted by heating.

7, 8, and 9 show examples for adjusting the reflectivity according to the difference in the input of the electric signal to the reflectivity variable mirror 11 (that is, the difference in the current injection waveform). The phase change material is generally in an amorphous state after film formation. Further, as shown in FIGS. 1 and 2, the phase change material has optical characteristics corresponding to the crystallization temperature due to the difference in the subsequent crystallization temperature. Further, like the RAM type optical recording medium using the phase change material, the phase change material can be brought into an amorphous state by heating the phase change material to a high temperature and then rapidly cooling it.
The reflectivity variable mirror 11 according to the present embodiment uses the characteristics of the phase change material, makes the initial state of the phase change material films 19 and 23 amorphous, and then heats to a temperature at which crystallization is performed. The phase change material films 19 and 23 are crystallized. In order to make the phase change material films 19 and 23 crystallized under a certain condition into a crystallized state under other conditions, the phase change material films 19 and 23 are heated to a higher temperature and then rapidly cooled to bring the phase change material films 19 and 23 into an initial state. After returning to the amorphous state, a predetermined crystallization temperature is set. Thereby, the reflectance can be adjusted.

FIG. 7 shows an example of the waveform (P1) of the current injected into the heater when the crystallization state is relatively low. FIG. 8 shows the waveform (P2) of the current injected into the heater when the crystallization state is relatively high. FIG. 9 shows the waveform (P3) of the current injected into the heater in the amorphous state.
7, 8, and 9, the horizontal axis is time, and the vertical axis is the current injected into the heater, but the vertical axis can also be expressed as supply energy (heater power). In each figure, 31 indicates a heater power region (so-called set power region) that becomes a crystallization state after cooling, and 32 indicates a heater power region (so-called erase power region) that becomes an amorphous state after cooling. 7 to 9 show the supply of a plurality of short pulse energy. Here, the supply energy is set to a plurality of short pulses so as to suppress the heat conduction in the in-plane direction and reduce the heat distribution in the heating region, but the pulse-like waveform is not always necessary. .

  As described above, the reflectivity adjusting method of the reflectivity variable mirror 11 according to the present embodiment can be adjusted by changing the crystallization temperature, but when changing the reflectivity once set. The reflectance can be adjusted with good reproducibility by performing the crystallization treatment after the amorphous state.

  Further, in the reflectivity variable mirror 11 of the present embodiment, since the relationship between the state of the phase change material and its dielectric constant is strong, the phase change material films 19 and 23 are formed in the configuration shown in FIG. Silicon films 17 and 20 and silicon films 20 and 25, which are conductive materials, are formed so as to be sandwiched, and the state of the phase change material films 19 and 23 is monitored by monitoring the capacitance between the conductive materials. Can be monitored. That is, the state of the phase change material films 19 and 23 can be monitored electrically. Therefore, the reflectivity variable mirror 11 according to the present embodiment has a feature that in addition to being able to adjust the reflectivity by inputting an electrical signal, the state can be monitored by monitoring the electrical signal. .

  FIG. 10 shows an embodiment of an optical power attenuator according to the present invention. In the optical power attenuator 41 according to the present embodiment, a plurality of laminated films 13 are formed on a common transparent substrate, for example, a glass substrate 42, corresponding to a plurality of incident lights Lin, and a plurality of reflectivity variable mirrors 11 are formed. The variable reflectivity mirror device 45 is formed, and a common beam splitter 43 is disposed above the variable reflectivity mirror device 45 so as to face each reflectivity variable mirror 11. In this example, five reflectivity variable mirrors 11 [11 1] each having a laminated film 13 [131, 132, 133, 134, 135] with respect to five incident lights Lin [Lin1, Lin2, Lin3, Lin4, Lin5]. , 112, 113, 114, 115] are arranged in a line, for example, and output light Lout [Lout1, Lout2, Lout3, Lout4, Lout5] having a light amount (reflected light amount) corresponding to the set reflectance is obtained. Configured to be.

  In the optical power attenuator 41 of the present embodiment, each incident light Lin1, Lin2, Lin3, Lin4, Lin5 is incident perpendicularly on the reflectivity variable mirrors 111, 112, 113, 114, 115 through the beam splitter 43. Reflected light reflected according to the reflectivity set by the reflectivity variable mirrors 111, 112, 113, 114, and 115 is reflected by 90 ° by the beam splitter 43, and the amount of light based on the set reflectivity is set. Output lights Lout1, Lout2, Lout3, Lout4, and Lout5 are output.

  FIG. 11 shows another embodiment of the optical power attenuator according to the present invention. The optical power attenuator 47 according to this embodiment has a plurality of common transparent substrates, for example, a glass substrate 42, and in this example, the optical characteristics described above change corresponding to three incident lights Lin [Lin1, Lin2, Lin3]. A multilayer film 49 [491, 492, 493] having a thin film is formed to form a plurality of, ie, three reflectivity variable mirrors 48 [481, 482, 483]. In this optical power attenuator 47, the reflectivity variable mirror 11 optimized with respect to the substrate 42 when the incident light Lin incident angle and the outgoing angle of the output light Lout are required angles, in this example, 45 °, is used. Each of the variable reflectivity mirrors 11 corresponds to each incident light Lin, and is configured to obtain output light Lout having a light amount (reflected light amount) in which the reflectivity is set in accordance with each mirror.

  FIG. 12 shows an embodiment of a laminated film 49 in which the optical characteristics constituting the reflectivity variable mirror 48 change. As shown in FIG. 12, the laminated film 491 of the present embodiment includes a silicon oxide (SiO2) layer 51, an aluminum film 52, a silicon oxide (SiO2) film 53, a silicon film 54, and silicon nitride (SiN). A film 55, a phase change material film (PC) 56, a ZnS-SiO2 film 57 (including a thickness of 0 nm as will be described later), and a silicon oxide layer 58 are sequentially stacked. As a specific example, the stacked film 491 includes a silicon oxide film (n = 1.47), an aluminum film 52 with a thickness of 200 nm, a silicon oxide film with a thickness of 20 nm (n = 1.47) 53, and a silicon with a thickness of 60 nm. A film 54, a silicon nitride film (n = 2.0) 55 having a thickness of 100 nm, a phase change material film (phase modulation liquid crystal element shown in FIGS. 1 and 2) 56, a thickness of 0 to 0 The laminated film is composed of a 400 nm ZnS-SiO2 film 57 and a silicon oxide film (n = 1.47) 58. The silicon oxide layer 51 and the silicon oxide layer 58 correspond to the substrates 12 and 14 in FIG. 3, respectively.

  FIG. 13 shows the change in reflectance with respect to P-polarized light when the thickness of the ZnS-SiO2 film 57 is changed from 0 nm to 400 nm as a parameter in the structure of the laminated film 491. In FIG. 13, the mark ● represents the reflectance R in the amorphous state, the mark ▲ represents the reflectance R in the crystallization state at 175 ° C., the mark □ represents the reflectance R in the crystallization state at 250 ° C., and the mark ▼ represents the reflectance at 325 ° C. R and ♦ indicate the reflectance R in the crystallized state at 400 ° C. From the results shown in FIG. 13, it can be seen that the variable range of reflectivity can be adjusted by setting the film thickness of the ZnS-SiO2 film 57. For example, when the thickness of the ZnS-SiO2 film 57 is about 50 nm, an optical attenuator capable of adjusting the reflectance in the range of about 32% to 46% can be configured. When the thickness of the ZnS-SiO2 film 57 is about 120 nm, an optical attenuator capable of adjusting the reflectance in the range of about 18% to 28% can be configured.

  FIG. 14 shows another embodiment of the film thickness configuration of the laminated film 49 constituting the reflectivity variable mirror 48 of the optical power attenuator 47 shown in FIG. In this embodiment, a configuration example in which a laminated film is arranged on the surface of a substrate is shown. As shown in FIG. 14, the laminated film 492 according to the present embodiment includes a silicon oxide (SiO2) layer 51, an aluminum film 52, a silicon oxide (SiO2) film 53, a silicon film 54, and silicon nitride (SiN). ) Film 55, phase change material film (PC) 56, ZnS-SiO2 film 57 (including a film thickness of 0 nm as described later), and silicon oxide film 59 are sequentially stacked. As a specific example, the stacked film 492 includes a silicon oxide film (n = 1.47), an aluminum film 52 with a thickness of 200 nm, a silicon oxide film (n = 1.47) 53 with a thickness of 20 nm, and a silicon with a thickness of 20 nm. A film 54, a silicon nitride film (n = 2.0) 55 with a thickness of 10 nm, a phase change material film (phase modulation liquid crystal element shown in FIGS. 1 and 2) 56, a thickness of 0 to 0 The laminated film is composed of a 400 nm ZnS-SiO2 film 57 and a 0.01 nm thick silicon oxide film (n = 1.47) 59. The silicon oxide layer 51 corresponds to the substrate 12 of FIG.

  FIG. 15 shows the reflectance of P-polarized light when the film thickness of the ZnS-SiO2 film 57 is changed from 0 nm to 400 nm using the crystallization temperature and amorphous state of the phase change material as parameters in the configuration of the laminated film 492. Shows changes. In FIG. 13, the mark ● represents the reflectance R in the amorphous state, the mark ▲ represents the reflectance R in the crystallization state at 175 ° C., the mark □ represents the reflectance R in the crystallization state at 250 ° C., and the mark ▼ represents the reflectance at 325 ° C. R and ♦ indicate the reflectance R in the crystallized state at 400 ° C. From the results shown in FIG. 15, there is almost no change in the reflectance when the thickness of the ZnS-SiO2 film 57 is around 50 nm and 220 nm, but the reflectance is different in other ranges of the thickness of the ZnS-SiO2 film 57. It can be seen that the reflectivity varies depending on the processing temperature of the phase change material film 56. It can be seen that the optical power attenuator and the reflectivity variable mirror of the present embodiment can operate even when a laminated film is disposed on the surface of the substrate.

FIG. 16 shows another embodiment of the optical power attenuator according to the present invention. The optical power attenuator 61 according to the present embodiment is configured by two-dimensionally arranging a plurality of reflectivity mirrors 64 [64 1 to 648] in this example on a substrate 63. Each of the variable reflectivity mirrors 64 has a laminated film 62 [621 to 628] whose optical characteristics change as described above. A heater film 68 is formed on the upper surface of the laminated film 62 and is connected to both ends of the heater film 68. Electrodes (conductive patterns) 66 and 67 to be formed are formed. In this example, eight reflectivity variable mirrors 641 to 648 are arranged in two rows, and individual electrodes 661 to 668 are connected to one end of each heater film 68 of each of the reflectivity variable mirrors 641 to 628. Each electrode is connected to a common electrode 67 at the other end. The common electrode 67 is formed so as to cross the central portion where the reflectivity variable mirrors 64 are arranged in two rows. As described above, the laminated film 62 is formed of a thin film that includes a thin film whose optical characteristics change depending on the processing conditions of the materials, for example, a phase change material film.
Then, individual incident light is incident on each of the reflectivity variable mirrors 64 and reflected to obtain output light having a light amount corresponding to the optical characteristic of each reflectivity variable mirror 64, that is, the reflectivity. Reference numeral 69 denotes a light spot position.

  According to the optical power attenuator 61 of the present embodiment, an optical power attenuator having a multi-array reflectivity variable mirror that could not be realized by the conventional optical power attenuator using the optical waveguide shown in FIG. Can be configured.

  The reflectivity variable mirror and the optical power attenuator described in the above embodiment are a part of the configuration example of the present invention. The present invention has a reflectivity variable mirror in which the reflectivity can be adjusted by changing the optical characteristics of a laminated film having a thin film whose optical characteristics change by external energy input, and the reflectivity variable mirror thereof The invention relates to an optical power attenuator.

  Since the reflectivity variable mirrors 11 and 41 shown in FIGS. 3 and 10 and the optical power attenuator using the reflectivity mirrors 11 and 41 are incident on the substrate perpendicularly, Since it has a characteristic that it is not affected by the polarization direction of light, it can be applied to circularly polarized incident light as it is. That is, although not shown, a quarter wave plate can be disposed between the beam splitter and the reflectivity variable mirror by using the beam splitter as a polarizing beam splitter (PBS).

  In the reflectivity variable mirror having the configuration shown in FIGS. 4 and 12, an example is shown in which glass substrates are arranged on both sides, but one side is made of a coating-type material, for example, a UV curable adhesive. There may be.

  In the above embodiment, Ge2 Sb2 Te5 has been described as an example of the phase change material. However, in the reflectivity variable mirror, the optical power attenuator, and the driving method and usage of the optical power attenuator of the present invention, the phase change is used. Even if the material is not limited to Ge2 Sb2 Te5, the transmittance and reflectance of the multilayer film can be optimally designed. Therefore, the material of the phase change material is not limited to Ge2 Sb2 Te5. Furthermore, in the description of the reflectivity variable mirror of the embodiment, the description has been given using the wavelength of 1550 nm as an example, but the application range of the reflectivity variable mirror of the present invention is not limited to the wavelength range of 1550 nm, By performing the optimum design of the transmittance and reflectance of the multilayer film for the 1300 nm band, the multilayer film can be used in the 1300 nm band.

It is a graph which shows the relationship between the refractive index n and wavelength of a phase change material which used the crystallization temperature and amorphous state for description of this invention as parameters. It is a graph which shows the relationship between the imaginary refractive index k of the phase change material which used the crystallization temperature used for description of this invention, and an amorphous state as a parameter, and a wavelength. It is a schematic block diagram which shows one Embodiment of the reflectance variable mirror which concerns on this invention. It is sectional drawing which shows the film | membrane structure of the laminated film which comprises the reflectance variable mirror of FIG. FIG. 5 is a graph showing the relationship between the film thickness of the silicon oxide film of the laminated film of FIG. 4 and the reflectance, using the crystallization temperature and the amorphous state of the phase change material as parameters. It is a specific block diagram of the reflectivity variable mirror which concerns on one Embodiment of AB. It is a current wave form diagram which shows the waveform of the injection current to a heater in the case of making a phase change material into a comparatively low temperature crystallization state. It is a current wave form diagram which shows the waveform of the injection current to a heater in the case of making a phase change material into a comparatively high temperature crystallization state. It is a current wave form diagram which shows the waveform of the injection current to a heater in the case of making a phase change material into an amorphous state. It is a block diagram which shows one Embodiment of the optical power attenuator which concerns on this invention. It is a block diagram which shows other embodiment of the optical power attenuator which concerns on this invention. It is sectional drawing which shows one Embodiment of the laminated film of the reflectance variable mirror of FIG. 13 is a graph showing the relationship between the film thickness and reflectance of the ZnS-SiO2 film constituting the laminated film of FIG. 12, using the crystallization temperature and the amorphous state of the phase change material as parameters. It is sectional drawing which shows other embodiment of the laminated film of the reflectance variable mirror of FIG. FIG. 15 is a graph showing the relationship between the film thickness and the reflectance of the ZnS—SiO 2 film constituting the laminated film of FIG. 14 using the crystallization temperature and the amorphous state of the phase change material as parameters. It is a block diagram which shows other embodiment of the optical power attenuator using the multi-variable reflectivity mirror which concerns on this invention. It is a block diagram which shows the example of the conventional optical attenuator.

Explanation of symbols

  11, 11 1 to 115,... Reflectivity variable mirror, 12, 14, transparent substrate, 13, 131 to 135, laminated film, 4, transparent member, 15, 43, beam splitter, 17, 25 ... silicon film, 18, 24 ... silicon nitride film, 19, 23 ... phase change material film, 20, 22 ... silicon oxide film, 41, 47, 61 ... optical power Attenuator, 48 [481 to 485] ... Reflectance variable mirror, 49 [491 to 495] ... Laminated film, 491, 492 ... Laminated film, 51, 53, 58 ... Silicon oxide film, 52 .. Aluminum film, 54... Silicon film, 55... Silicon nitride film, 56... Phase change material film, 57... ZnS-SiO2 film, 59. 625] ... Laminated film, 63 ... base Plate, 64 [641 to 645] ... Reflectance variable mirror, 69 ... Light spot

Claims (27)

A laminated film including a thin film having a different refractive index in each of a plurality of different states,
The reflectivity variable mirror, wherein the reflectivity of the light applied to the laminated film is adjusted by changing the reflectance of the laminated film by controlling the state of the thin film. The variable reflectivity mirror according to claim 1, wherein the thin film is formed of a phase change material. The reflectivity variable mirror according to claim 1, wherein the reflectivity of the laminated film is adjusted by adjusting thermal energy supplied to the thin film. The variable reflectivity mirror according to claim 1, wherein the laminated film has a heat generating function for generating heat from the thin film. 5. The reflectivity variable mirror according to claim 4, wherein a conductive film is formed on both sides of the thin film constituting the laminated film. It is composed of a laminated film including thin films having different refractive indexes in each of a plurality of different states, and the reflectance of the laminated film is changed by controlling the state of the thin film, and the reflected energy of light irradiated on the laminated film is changed. Adjustable reflectivity mirror is placed in the optical path,
An optical power attenuator for adjusting the amount of light reflected by the optical path. The optical power attenuator according to claim 6, wherein the thin film is formed of a phase change material. The optical power attenuator according to claim 6, wherein the reflectance and transmittance of the laminated film are changed by thermal energy supplied to the thin film. The optical power attenuator according to claim 6, wherein the laminated film has a heat generating function for generating heat from the thin film. The optical power attenuator according to claim 6, wherein a conductive film is formed on both sides of the thin film constituting the laminated film. It is composed of a laminated film including thin films having different refractive indexes in each of a plurality of different states, and the reflectance of the laminated film is changed by controlling the state of the thin film, and the reflected energy of light irradiated on the laminated film is changed. A plurality of variable reflectivity mirrors to be adjusted are formed on one substrate,
Each of the variable reflectivity mirrors is disposed in each of a plurality of optical paths;
An optical power attenuator that adjusts the amount of light reflected by each of the optical paths. The optical power attenuator according to claim 11, wherein the thin film is formed of a phase change material. The optical power attenuator according to claim 11, wherein the reflectance and transmittance of each laminated film are changed by thermal energy supplied to the thin film. The optical power attenuator according to claim 11, wherein the laminated film has a heat generating function for generating heat from the thin film. The optical power attenuator according to claim 11, wherein a conductive film is formed on both sides of the thin film constituting the laminated film. It is composed of a laminated film including thin films having different refractive indexes in each of a plurality of different states, and the reflectance of the laminated film is changed by controlling the state of the thin film, and the reflected energy of light irradiated on the laminated film is changed. For the variable reflectivity mirror to be adjusted,
The method of driving the variable reflectivity mirror, wherein the reflectivity variable mirror is driven while electrically monitoring the state of the thin film. The method of driving a variable reflectivity mirror according to claim 16, wherein the thin film is formed of a phase change material. 18. The method of driving a reflectivity variable mirror according to claim 17, wherein the adjustment of the reflectance of the laminated film is performed by once returning the phase change material to an amorphous state and then changing to another crystal state. The method of driving a reflectivity variable mirror according to claim 17, wherein the method of electrically monitoring the state of the thin film comprises a method of monitoring capacitance. A method of driving the variable reflectivity mirror, wherein the state of the variable reflectivity mirror is inspected by electrically monitoring the state of the thin film. The method of driving a variable reflectivity mirror according to claim 17, wherein the state of the thin film is electrically monitored to adjust the amount of light reflected by the variable reflectivity mirror. It is composed of a laminated film including thin films having different refractive indexes in each of a plurality of different states, and the reflectance of the laminated film is changed by controlling the state of the thin film, and the reflected energy of light irradiated on the laminated film is changed. For the optical power attenuator that adjusts the amount of light reflected by the reflectivity variable mirror to be adjusted and disposed in the optical path,
The optical power attenuator driving method, wherein the optical power attenuator is driven while electrically monitoring the thin film. The method of driving an optical power attenuator according to claim 22, wherein the thin film is formed of a phase change material. 24. The method of driving an optical power attenuator according to claim 23, wherein the output adjustment of the optical power attenuator is performed after the phase change material is once returned to an amorphous state and then in another crystalline state. 24. The method of driving an optical power attenuator according to claim 23, wherein the method of electrically monitoring the state of the thin film comprises a method of monitoring electrostatic capacity. The method for driving an optical power attenuator according to claim 23, wherein the state of the thin film is electrically monitored to check the state of the optical power attenuator. The method for driving an optical power attenuator according to claim 23, wherein the state of the thin film is electrically monitored to adjust the light amount of the optical power attenuator.

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