JP2006343555A - Light switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light switch which has an excellent reproducibility of mirror angle and is easily controlled. <P>SOLUTION: The light switch reflects incident light on a mirror face 1 to emit the light, the mirror face 1 is formed on the surface of a deformable film 2 deformable in the film thickness direction so that the incident and emitting angles are varied according to the deformed state of the deformable film 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical switch using a mirror, and more particularly to an optical switch with good mirror angle reproducibility and easy control.

  With the spread of the Internet in recent years, the speed and capacity of optical communication networks have been remarkably advanced. As a method for increasing the optical transmission capacity, a wavelength division multiplexing (WDM) communication system has been actively introduced. Accordingly, an optical switch with less wavelength dependence is required, and optical add / drop multiplexing (OADM) or optical cross-connect (OXC) that switches an optical signal as it is without converting the optical signal into an electrical signal. Expectations for Optical Cross Connect have increased.

  A MEMS (Micro Electro Mechanical System) system in which these basic elements can be integrated and collectively processed has attracted attention. When the MEMS technology is used, a small system can be integrated by three-dimensional microfabrication based on a semiconductor integrated circuit processing technology. The optical characteristics of the MEMS optical switch are characterized by a high extinction ratio and no wavelength dependence compared to the waveguide optical switch. In addition, there are expectations for downsizing, high-density, large-scale, non-blocking type, and low-power type that can self-hold the mirror angle.

  Non-blocking matrix optical switches intended for these are described in Patent Document 1 and Patent Document 2.

  As shown in FIG. 5, the optical switch of the background art is one in which two mirror bases 502 on which four movable mirrors 501 are formed on a substrate 503 by using MEMS technology. Each mirror base 502 is perpendicular to the substrate 503 and parallel to each other. Two optical input / output ports 507 formed by mounting a microlens 506 for flying signal light as parallel light in a space to a four-fiber array 505 connected with optical fibers 504 are arranged on a substrate 503. . These light input / output ports 507 face each other with the two mirror bases 502 interposed therebetween. In order to apply a magnetic field to each movable mirror 501, two permanent magnets 508 sandwiching two mirror bases 502 are arranged at an appropriate angle.

  The signal light incident from one light input / output port 507 is reflected by the movable mirror 501 in the incident-side mirror base 502 and reflected by one of the movable mirrors 501 in the output-side mirror base 502 and the other. The light is output from the optical input / output port 507. At that time, the optical fiber 504 from which the signal light is emitted can be switched by adjusting the angle of the movable mirror 501. An example of the optical path 509 is indicated by a dotted line.

  As shown in FIG. 6, each movable mirror 501 is supported by a gimbal structure so that it can rotate about the X axis and the Y axis. The Y-axis rotation unit 601 on which the movable mirror 501 is formed has two polyimide torsion bars located on the Y-axis from the X-axis rotation unit 602 provided away from the periphery of the Y-axis rotation unit 601. 603 is supported. The mirror surface that becomes the movable mirror 501 is formed of a thin film of Au. A fine coil 604 made of Cu plating is formed on the Y-axis rotating portion 601 so as to surround the movable mirror 501. A latch mechanism 605 for holding the movable mirror 501 at a predetermined angle around the Y-axis in a non-powered state is provided in the X-axis rotation unit 602.

  The X-axis rotation unit 602 is supported by two polyimide torsion bars 606 located on the X-axis from a mirror base 502 provided around the X-axis rotation unit 602. A fine coil 607 made of Cu plating is formed on the outer periphery of the X-axis rotation unit 602. The mirror base 502 is provided with a latch mechanism 608 for holding the movable mirror 501 at a predetermined angle around the X axis in a non-powered state.

  The operation will be described with reference to FIG. In the magnetic field B formed between the two permanent magnets 508, when a current i is passed through the fine coils 604 and 607 (the Y-axis rotating portion 601 and the X-axis rotating portion 602 are the entire surface in this figure), Lorentz force F is generated in each of the fine coils 604 and 607.

F = B × i
By this Lorentz force F, the Y-axis rotation unit 601 and the X-axis rotation unit 602 rotate. At that time, a torsional reaction force is generated in the torsion bars 603 and 606, and the rotation angles of the Y-axis rotation unit 601 and the X-axis rotation unit 602 are determined by the balance between the Lorentz force F and the reaction force. Therefore, the angle of the movable mirror 501 can be controlled to an arbitrary angle by changing the current i flowing through the fine coils 604 and 607.

JP 2002-31767 A JP 2003-329948 A

  In the background art, the movable mirror is supported by a torsion bar, and a torsional reaction force is generated in the torsion bar. However, since a plastic deformation also occurs in the torsion bar, it is difficult to obtain reproducibility for the angle of the movable mirror.

  In addition, in order to accurately control the angle of the movable mirror, it is necessary to detect the angle of the movable mirror and feed back the detected angle information to the current i to correct the shift amount. However, conventionally, light is used for angle detection of the movable mirror, and there is a problem that the movable mirror control system including this angle detection becomes complicated.

  In addition to this, when manufacturing the optical switch of the background art by the MEMS technology, in order to rotate the X-axis and Y-axis rotating parts against the reaction force of the torsion bar, the unit area or unit volume is required. There is a problem of lack of power.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical switch that solves the above-described problems, has a good mirror angle reproducibility, and is easy to control.

  In order to achieve the above object, the present invention provides an optical switch that reflects incident light by a mirror surface and emits it, and the mirror surface is formed on the surface of a deformable film that can be deformed in the film thickness direction. The incident / exit angles of light differ according to the above.

  The deformation state of the deformation film may include at least two states, a convex state where the mirror surface is convex and a concave state where the mirror surface is concave.

  A through hole may be formed in the pressure vessel, the through hole may be covered with the deformation membrane, and the deformation membrane may be deformed by changing the pressure in the pressure vessel.

  The mirror surface may be a first electrode, a second electrode facing the electrode may be provided, and the deformation state of the deformation film may be detected from the capacitance between the first and second electrodes.

  The incident optical path to the mirror surface connects one point of the mirror surface when the deformation film is most deformed in one direction and the other point of the mirror surface when the deformation film is most deformed in the opposite direction. It may be on the line.

  The present invention exhibits the following excellent effects.

  (1) The reproducibility of the mirror angle is better than the background technology using a torsion bar.

  (2) Control is simpler than the background art in which the mirror angle is optically detected.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the optical switch according to the present invention reflects incident light by a mirror surface 1 and emits it. In this embodiment, the mirror surface 1 swells like a dome, and is circular when viewed from the front of the mirror surface 1. As shown in the drawing, a plurality of mirror surfaces 1 may be arranged in an array in the vertical and horizontal directions. In the present invention, since the actuator that drives each mirror surface 1 does not appear on the surface on which the mirror surface 1 is arranged, the arrangement density can be increased. For example, the mirror surface 1 has a diameter of 500 μm. The incident light (incident signal light) Li is reflected so that the incident angle and the outgoing angle with respect to the tangent A of the mirror surface 1 are equal to each other to become outgoing signal light Lo. For simplicity of explanation, it is assumed that the incident signal light Li is incident on the center of the mirror surface 1 and the tangent line A is parallel to the diameter of the circle around the mirror surface 1.

  Each drawing in FIG. 2 shows a mirror surface in a cross section along a tangent line A. As shown in FIG. 2 (a), the optical switch according to the present invention has a mirror surface 1 formed on the surface of a deformation film 2 that can be deformed in the film thickness direction, and the light switch according to the deformation state of the deformation film 2. The incident and outgoing angles are different. The mirror surface 1 is made of an Au thin film, and the deformation film 2 is made of a Poly-Si thin film. A Cr thin film is provided as an adhesion layer 3 between the mirror surface 1 and the deformation film 2. A deformable mirror 4 is formed by the three-layer structure of these thin films. In this embodiment, the mirror surface 1 is circular when viewed from the front as described in FIG. 1, and is circular when viewed in cross section as shown in FIG. That is, the mirror 4 is formed in a dome shape. The periphery of the mirror 4 is fixed to the support 5. Therefore, the deformation of the mirror 4 is conspicuously generated in the central portion, and is smaller as it approaches the peripheral portion.

  The deformation state of the deformable film 2 includes a convex state in which the mirror surface 1 is convex as shown in FIG. 2A, a concave state in which the mirror surface 1 is concave as shown in FIG. 2C, and a state as shown in FIG. The mirror surface 1 is flat. Here, the two states of the convex state where the deformable film 2 is most deformed in one direction and the concave state where the deformable film 2 is most deformed in the opposite direction are used for optical path switching. This is because it is easier to stably control the convex state and the concave state than the transitional state as shown in FIG. In FIG. 2, the actuator that drives the deformation film 2 to be deformed is not clarified, but by configuring an appropriate actuator, the initial state where no driving force is applied is changed to a convex state, and the driving force is sufficiently applied. The deformed state may be a concave state, or the initial state where no driving force is applied may be a concave state, and the sufficiently deformed state by applying a driving force may be a convex state. Alternatively, both the convex state and the concave state may be set to the initial state, and the driving force may be applied only in the transient state.

  Now, as shown in FIG. 2A, the incident signal light Li is incident on the vertex 26, which is one point on the mirror surface in the convex state. The optical path of the incident signal light Li is assumed to be stationary. At this time, the incident signal light Li is reflected so that the incident angle and the outgoing angle with respect to the tangent to the mirror surface 1 are equal to each other to become the outgoing signal light Lo1. The inclination of the tangent to the mirror surface 1 can be referred to as the mirror angle.

  Next, as shown in FIG. 2C, the deformation film 2 is deformed into a concave state. Thereby, the mirror 4 becomes an inverted dome shape. Since the optical path of the incident signal light Li does not move, the incident signal light Li in the concave state further advances straight due to the disappearance of the apex 26 (FIG. 2A), and reaches a point 27 near the periphery of the mirror 4. Incident. Since the tangential slope (mirror angle) of the mirror surface 1 at this point 27 is different from the tangential slope at the vertex 26, when the incident signal light Li is reflected so that the incident angle and the outgoing angle with respect to the tangential line are equal, the outgoing signal light Lo2 is reflected. Advances at an angle different from that of the outgoing signal light Lo1. In this way, the optical path is switched.

  As described above, in the embodiment of FIG. 2, the dome-shaped mirror 4 is deformed in the film thickness direction, so that deformation without plastic deformation such as a torsion bar is realized. Since there is no plastic deformation, even if the deformation is repeated, the same magnitude of deformation can be reproduced with the same driving force. Therefore, reproducibility of the mirror angle can be obtained.

  The actuator will be described with reference to FIG. As shown in FIG. 3A, a through hole 32 is formed in the pressure vessel 31, and the through hole 32 is covered with the deformation film 2 described in FIG. The pressure vessel 31 is sealed except for the fluid passage 33. The fluid passage 33 is connected to a pressure source (not shown) that can be pressurized and depressurized, a switching valve, and the like, so that pressure fluid such as air can be introduced and discharged. Needless to say, the pressure vessel 31 is rigid enough not to be deformed regardless of the internal pressure. On the other hand, the deformable membrane 2 can be deformed by having appropriate flexibility or elasticity. Therefore, the deformation membrane 2 can be deformed by changing the pressure in the pressure vessel 31.

  When attention is paid to the deformation state of the deformation film 2, FIG. 3A corresponds to the convex state described with reference to FIG. At this time, the deformation membrane 2 is in an initial state where no driving force is applied, and the internal pressure of the pressure vessel 31 is P0. On the other hand, FIG. 3B corresponds to the concave state described in FIG. Also at this time, the deformation membrane 2 is in an initial state where no driving force is applied, and the internal pressure of the pressure vessel 31 is set to P1. P0> P1. If the atmospheric pressure is atmospheric pressure, P0> atmospheric pressure> P1.

  Now, as shown in FIG. 3A, when the internal pressure of the pressure vessel 31 is P0 and the deformable membrane 2 is in a convex state and no driving force is applied, the internal pressure is P1 through the fluid passage 33. Suppose the pressure is reduced to Since the atmospheric pressure> P1, the deformation film 2 is pushed into the through hole 32 and changes to the concave state of FIG. After that, even if the decompression drive is stopped, the internal pressure of the pressure vessel 31 is maintained at P1, so that the concave state is maintained.

  As shown in FIG. 3B, when the internal pressure of the pressure vessel 31 is P1 and the deformable membrane 2 is in a concave state and no driving force is applied, the internal pressure becomes P0 via the fluid passage 33. It is assumed that pressure is applied. Since P0> atmospheric pressure, the deformable membrane 2 bulges out of the through hole 32 and changes to the convex state of FIG. Thereafter, even if the pressurization driving is stopped, the internal pressure of the pressure vessel 31 is maintained at P0, so that the convex state is maintained.

  Thus, in the present invention, since the deformation of the deformation film 2 is in the film thickness direction, fluid pressure can be used as a force for deforming the deformation film 2. The actuator can be arranged only on the back side of the mirror surface 1. As a result, the structure for the actuator and the structure for supporting the mirror surface are eliminated in the space through which the optical path passes, and the optical system is simplified.

  Further, although the optical switch of the present invention is manufactured by the MEMS technology, since the deformable film 2 is deformed by the fluid pressure, there is no problem of insufficient power per unit area or unit volume.

  Furthermore, the actuator drive source (pressure source, switching valve, etc.) not shown in the figure can be provided in a place not directly related to the mirror 4. As a result, the structure of the optical switch is simplified, and there is an advantage that it is easy to cope with maintenance and failure.

Next, state detection will be described with reference to FIG. As can be seen from FIG. 4A, this embodiment is applied to the one using the actuator of FIG. Here, the mirror surface 1 made of metal is used as the first electrode 41, and the second electrode 42 facing the electrode 41 is provided. That is, the second electrode 42 is provided on the bottom surface of the pressure vessel 31. Needless to say, FIG. 4A corresponds to the convex state and FIG. 4B corresponds to the concave state. In general, the capacitance C between the electrodes is a function of the dielectric constant ε of the interelectrode medium, the electrode interval d, and the electrode area S. When the electrodes are parallel plates,
C = εS / d
It becomes. The electrostatic capacitance generated between the first electrode 41 and the second electrode 42 also substantially conforms to the above formula. When the electrode interval between the first electrode 41 and the second electrode 42 changes from d0 to d1, the capacitance also changes accordingly. Therefore, the deformation state of the deformation film 2 can be detected from the capacitance.

  The desired amount of deformation can be accurately controlled by feeding back the detected capacitance to the fluid pressure to which it is applied. This control is simpler than the control based on the optical angle detection of the background art. When performing feedback control using electrostatic capacity, the correlation between the electrostatic capacity, the deformation amount of the deformation film, the fluid pressure (pressure vessel internal pressure), and the mirror angle is measured in advance, and the control amount is determined based on the data. Should be calibrated.

It is an external view of the mirror surface of the optical switch which shows one Embodiment of this invention. (A)-(c) is sectional drawing of the mirror surface of the optical switch which shows one Embodiment of this invention. (A), (b) is sectional drawing of the optical switch which shows one Embodiment of this invention. (A), (b) is sectional drawing of the optical switch which shows one Embodiment of this invention. It is a perspective view of the optical switch of background art. It is an enlarged front view of the movable mirror of the optical switch of FIG. It is an operation | movement principle figure of the optical switch of background art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mirror surface 2 Deformation film 31 Pressure vessel 32 Through-hole 41 First electrode 42 Second electrode

Claims (5)

  In an optical switch that reflects incident light by a mirror surface and emits it, the mirror surface is formed on the surface of a deformable film that can be deformed in the film thickness direction so that the light incident / exit angle varies depending on the deformed state of the deformed film. An optical switch characterized by that.   2. The optical switch according to claim 1, wherein the deformation state of the deformation film includes at least two states, a convex state in which the mirror surface is convex and a concave state in which the mirror surface is concave.   3. The optical switch according to claim 1, wherein a through hole is formed in the pressure vessel, the through hole is covered with the deformation membrane, and the deformation membrane is deformed by changing the pressure in the pressure vessel. .   The mirror surface is used as a first electrode, a second electrode facing the electrode is provided, and the deformation state of the deformation film is detected from the capacitance between the first and second electrodes. The optical switch according to claim 1. The incident optical path to the mirror surface connects one point of the mirror surface when the deformation film is most deformed in one direction and the other point of the mirror surface when the deformation film is most deformed in the opposite direction. The optical switch according to claim 1, wherein the optical switch is on a line.

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