JP2013083856A - Deflection element and alignment method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deflection element and an alignment method for performing more accurate alignment.SOLUTION: An alignment pattern 6 has a shape in which a width of a reflection surface of a wavelength separation direction changes as the pattern 6 is away from an axis parallel to an X-axis. Therefore, when the alignment pattern 6 is irradiated with input light, a band width of reflected light by the alignment pattern 6 is capable of having an extremal value when a MEMS mirror array chip 5 is not positionally deviated from a Y-axis. As a result, only if the position of the MEMS mirror array chip 5 in the Y-axis direction is adjusted on the basis of the band width of the reflected light, alignment of the MEMS mirror array chip 5 in the Y-axis direction can be performed.

Description

  The present invention relates to a deflection element and a deflection element alignment method, and more particularly to a deflection element having an alignment pattern and a deflection element alignment method.

  In recent years, in the field of optical communication, it is possible to perform large-capacity optical transmission using a single optical fiber by WDM (Wavelength Division Multiplexing) technology, in which one optical signal is associated with one wavelength and wavelength-division multiplexed. It has been realized. With the development of such optical communication technology, an optical switch equipped with a deflecting element is in the spotlight as a device for switching a path without converting an optical signal into an electric signal or the like. For example, a wavelength selective optical switch that can select an arbitrary wavelength from several tens of wavelengths and output the selected wavelength to any of a plurality of output fibers (see, for example, Patent Document 1) has been proposed. An example of this wavelength selective optical switch (WSS: Wavelength Selective Switch) is shown in FIG.

  The wavelength selective optical switch shown in FIG. 11 includes a fiber array 1 composed of a plurality of optical fibers, a microlens array 2, a condensing lens 3, a 4f optical system 4, and a plurality of MEMS (Micro Electro Mechanical System) mirrors. The MEMS mirror array chip 100 having elements and functioning as a deflecting element is arranged in this order along one direction (hereinafter referred to as “Z-axis direction”).

  The fiber array 1 has a configuration in which a plurality of optical fibers (seven in the case of FIG. 11) having an optical axis parallel to the Z axis are arranged in parallel in the Y axis direction orthogonal to the Z axis. The fiber 1a is used as an input port, and the other six optical fibers 1b are used as output ports. In addition, although the optical fiber array 1 mentioned above uses the optical fiber 1a located in the center among several optical fibers as an input port, the position of an input port is not limited to this, For example, it is in the end of an optical fiber array. A located port may be used.

  The microlens array 2 has a plurality of microlenses arranged in parallel along the Y-axis direction so as to face each optical fiber end face of the fiber array 1. Although the microlens is used to enlarge the mode field radius of the input / output optical fiber, it may be omitted if not necessary.

  The 4f optical system 4 includes a first lens 41 and a second lens 42 each having a focal length f, and a transmissive diffraction grating 43. The first lens 41, the diffraction grating 43, and the second lens 42 are arranged in this order. They are arranged from the condenser lens 3 on the positive side in the Z-axis direction at intervals of f. Among these, the first lens 41 is disposed at a position separated from the condenser lens 3 by a total distance of the focal length of the condenser lens 3 and the focal length f of the first lens 41.

  As shown in FIG. 12, the MEMS mirror array chip 100 includes a base portion 101 having a substantially rectangular shape in plan view, and a plurality of MEMS mirror elements 102 disposed inside the base portion 101 and arranged at predetermined intervals in the X-axis direction. Is provided. The MEMS mirror element 102 includes a mirror 102a that is rotatable in the X-axis direction and the Y-axis direction. In addition, since the structure of each MEMS mirror element 102 is described, for example in patent document 1, the detailed description is abbreviate | omitted in this specification. Further, although the wavelength selective optical switch described above has been described by taking the configuration of one input and multiple outputs as an example, the configuration of other inputs and one output may be used. Furthermore, the diffraction grating 43 is not limited to the transmission type, and may be a reflection type.

In such a wavelength selective optical switch, when WDM signal light that is wavelength-separated by a predetermined number of channels at a predetermined wavelength interval is input to the input port 1a of the fiber array 1, the WDM signal light is converted into a microlens array. 2. The light reaches the 4f optical system 4 through the condenser lens 3, enters the diffraction grating 43 through the first lens 41, and is demultiplexed into a predetermined number of wavelength channels. The demultiplexed light is aligned on the X axis of the focal plane opposite to the second lens 42 to form a beam waist. At this beam waist position, the MEMS mirror array chip 100 in which the MEMS mirror elements 102 are arranged at an appropriate pitch corresponding to each channel is arranged. The arrangement of the beam waists of the demultiplexed light and the MEMS mirror elements 102 arranged in the X-axis direction at an appropriate pitch corresponding to each wavelength channel are arranged so as to spatially coincide. In this state, when the MEMS mirror element 102 is rotated about the X axis by a predetermined angle around the mirror 102a, the light irradiated on the MEMS mirror element 102 is reflected in a direction corresponding to the predetermined angle, and 4f optical It can be output from a predetermined output port 1b via the system 4, the condenser lens 3 and the microlens array 2. In this way, by selectively rotating the mirror 102a of the MEMS mirror element 102 around the X axis, switching of output ports for each channel, so-called switching, can be performed selectively.
In the wavelength selective optical switch, the interval between wavelength channels is often displayed as a frequency for convenience, and in the following, the wavelength channel, the interval, and the band will be expressed using the frequency.

  When assembling such a wavelength selective optical switch, the MEMS mirror array chip 100 and other optical systems are arranged so that the beam waist of the demultiplexed light is positioned on the mirror 102a of the corresponding MEMS mirror element 102. It is important to perform accurate alignment.

If the MEMS mirror array chip 100 is displaced in the demultiplexing direction (X-axis direction), the beam waist position of the frequency-separated signal light is X from the center position of the mirror 102a corresponding to each frequency channel. Due to the shift in the axial direction, the effective pass band is narrowed and it is difficult to pass high-speed signals.
Therefore, in order to suppress such positional deviation in the X-axis direction, in alignment of the MEMS mirror array chip 100, monitor light is input to the input port 1a from a broadband light source such as ASE (Amplified Spontaneous Emission), and the MEMS mirror element The spectral shape of the light reflected by the mirror 102a and output from the input port 1a is observed. Specifically, broadband light (hereinafter referred to as “ASE light”) input from the ASE light source via the input port 1a is frequency-separated by the condenser lens 3 and the 4f optical system 4 and is parallel to the X axis. The MEMS mirror array chip 100 is irradiated with band-shaped light having a specific frequency axis. Since each mirror 102a on the MEMS mirror array chip 100 has a width in the X-axis direction of the reflection region corresponding to a frequency band of a signal transmitted through each channel, the band-like light is rectangular with a predetermined bandwidth. The light is cut into a shape and reflected, and the reflected light is incident on the input port 1a through the 4f optical system 4 and the condenser lens 3. When the optical spectrum shape of the reflected light is observed by the optical spectrum analyzer, a rectangular spectrum cut out in a predetermined frequency band by each mirror 102a on the coordinate plane composed of the frequency axis and the light intensity axis is obtained for all channels. It is displayed and observed as a comb-like spectrum shape. The comb-like spectrum moves in the frequency axis direction when the MEMS mirror array chip 100 is moved in the X axis direction. Accordingly, the position of the MEMS mirror array chip 100 in the X-axis direction is adjusted by moving the MEMS mirror array chip 100 in the X-axis direction so that the center of each comb-like spectrum matches the desired frequency position. be able to. Further, by rotating the MEMS mirror array chip 100 around the Z axis so that the top of the comb-like spectrum has the same light intensity over all channels, the Z axis of the MEMS mirror array chip 100 is centered. It is also possible to correct the positional deviation in the rotational direction.

On the other hand, if the MEMS mirror array chip 100 is displaced in the Y-axis direction perpendicular to the arrangement direction (X-axis direction) of the MEMS mirror elements 102, a part of the beam is clipped by the MEMS mirror size, and the amount of reflected light is reduced. . Such positional deviation in the Y-axis direction is difficult to detect because the position in the frequency axis direction does not change even when the comb-like spectrum as described above is observed.
Therefore, conventionally, as shown in FIG. 12, in the MEMS mirror array chip 100, the both sides of the base 101 and the MEMS mirror elements 102 located at both ends of the MEMS mirror elements 102 arranged in the X-axis direction. Alignment in the Y-axis direction is performed by providing alignment patterns 110 in two regions on the base 101 between them and observing the spectral shape of light reflected from these alignment patterns 110 (see Patent Document 2). ).
The alignment pattern 110 is made of a material having a higher reflectance than the surrounding base 101 region, such as gold or aluminum, and a pair of opposing sides are parallel to the X axis and one diagonal line is along the Y axis. It has a substantially parallelogram-shaped planar shape. The parallelogram is formed such that its center of gravity is located on the same straight line as the center of each mirror 52a.

  The alignment of the MEMS mirror array chip 100 using such an alignment pattern 110 in the Y-axis direction is similar to the alignment in the X-axis direction described above, and light is input to the input port 1a from a broadband light source such as ASE. This is done by observing the spectral shape of the light output from 1a. Specifically, the ASE light input via the input port 1a is frequency-separated through the microlens array 2, the condensing lens 3 and the 4f optical system 4 to form a band-like light having a frequency axis parallel to the X axis. The band-like light is reflected by the alignment pattern 110, and the reflected light is incident on the input optical fiber 1a through the 4f optical system 4, the condensing lens 3 and the microlens array 2, and the optical spectrum of the reflected light is reflected by an optical spectrum analyzer. Observe the shape.

When the MEMS mirror array chip 100 is not displaced in the Y-axis direction, the strip-shaped light is irradiated to the entire parallelogram alignment pattern 110 without protruding from the alignment pattern 110 in the Y-axis direction. Then, the optical spectrum shape of the reflected light of the alignment pattern 110 observed by the optical spectrum analyzer is an isosceles triangle.
On the other hand, when the MEMS mirror array chip 100 is displaced in the Y-axis direction, the strip-shaped light protrudes from the alignment pattern 110 in the Y-axis direction, so that a part of the parallelogram alignment pattern 110 is irradiated. It becomes. Then, the optical spectrum shape of the reflected light of the alignment pattern 110 observed by the optical spectrum analyzer becomes a so-called trapezoidal shape in which the apex of the triangle is removed. Thus, the MEMS mirror array chip 100 is moved in the Y-axis direction while observing the spectrum shape so that the spectrum shape is an isosceles triangle, thereby performing alignment in the Y-axis direction.

JP 2009-229916 A JP 2009-104081 A

  However, when the beam waist diameter is larger than the alignment accuracy on the focal plane of the second lens 42 on the MEMS mirror array chip 100 side, even if the MEMS mirror array chip 100 moves the mirror array chip 100 in the Y-axis direction, Changes in the spectral shape of the reflected light may not appear sharply. For example, if the beam waist diameter in the Y-axis direction is 5 to 10 times the alignment accuracy, even if the beam protrudes twice from the one end of the alignment pattern 110 in the Y-axis direction, the loss is 0.2. Only a small amount of ˜0.5 dB changes, and it is difficult to discriminate the change of the spectrum shape from an isosceles triangle to a trapezoid. As described above, depending on the combination of the beam waist diameter, the required alignment accuracy, and the alignment pattern shape, the change in the spectral shape of the reflected light observed by the optical spectrum analyzer in the alignment step may be in the Y-axis direction of the MEMS mirror array chip 100. It does not necessarily have a sharp peak with respect to movement. For this reason, it has been difficult for the conventional method to accurately adjust the alignment in the Y-axis direction.

  Therefore, an object of the present invention is to provide a deflection element and an alignment method that can perform more accurate alignment.

  In order to solve the above-described problems, a deflection element according to the present invention is a deflection element that deflects input light separated according to wavelength, and has a reflectance different from that of the surroundings, and the wavelength of the input light. The width in the wavelength separation direction changes from the predetermined first axis parallel to the separation direction along the second axis that is orthogonal to the first axis and intersects the optical axis of the input light. An alignment pattern having a shape having an extreme value of the width in the wavelength separation direction is provided thereon.

  In the deflection element, the alignment pattern may have a point-symmetric shape with respect to an intersection of the first axis and the second axis. Here, the alignment pattern may have a rhombus shape in which one of the diagonal lines is parallel to the first axis and the other is parallel to the second axis. Further, the alignment pattern may have a drum shape in which the width in the wavelength separation direction at the central portion in the direction of the second axis is an extreme value. The alignment pattern may have a symmetrical shape with respect to the second axis. Here, the shape may be a pentagon. Furthermore, the alignment pattern may have an asymmetric shape with respect to the second axis. Here, the shape may be a kamaboko shape.

  In the deflection element, the alignment pattern may be arranged such that the center of the width that is the extreme value of the alignment pattern coincides with the position corresponding to the optical frequency grid.

  An alignment method according to the present invention is a deflection element alignment method for deflecting input light separated according to wavelength, and is provided on the deflection element and has a reflectance different from that of the surroundings, and the wavelength of the input light. A first step of irradiating the wavelength-separated light in the first axis direction to an alignment pattern whose width in the wavelength separation direction changes as it moves away from the predetermined first axis parallel to the separation direction; The width of the frequency band of the reflected light from the pattern is measured, and the position of the deflection element in the direction of the second axis perpendicular to the first axis and intersecting the optical axis of the input light is determined so that this width becomes an extreme value. And a second step of adjusting.

  According to the present invention, the width of the wavelength separation direction changes as the alignment pattern is separated from the predetermined first axis parallel to the wavelength separation direction of the input light along the second axis orthogonal thereto. In addition, by forming a shape having an extreme value of the width in the wavelength separation direction on the first axis, when the input light is irradiated to the alignment pattern, the width of the frequency band of the reflected light by the alignment pattern is Can be an extreme value when there is no displacement in the second axial direction. Thus, the alignment of the deflecting element in the second axial direction can be performed only by adjusting the position of the deflecting element in the second axial direction based on the width of the frequency band of the reflected light.

FIG. 1 is a diagram schematically showing a configuration of a wavelength selective optical switch according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing the configuration of the MEMS mirror array chip according to the embodiment of the present invention. FIG. 3 is a plan view schematically showing the configuration of the alignment pattern according to the embodiment of the present invention. FIG. 4 is a diagram schematically showing an apparatus configuration when aligning the MEMS mirror array chip according to the embodiment of the present invention. FIG. 5 is a flowchart showing an alignment method of the MEMS mirror array chip according to the embodiment of the present invention. FIG. 6 is a diagram for explaining changes in the wavelength spectrum and bandwidth of reflected light depending on the positional relationship between the alignment pattern and the beam waist according to the embodiment of the present invention. FIG. 7 is a diagram for explaining changes in the wavelength spectrum and bandwidth of reflected light depending on the positional relationship between the alignment pattern and the beam waist according to a modification of the embodiment of the present invention. FIG. 8 is a diagram for explaining a change in the bandwidth of the reflected light due to the positional relationship between the alignment pattern and the beam waist according to the modification of the embodiment of the present invention. FIG. 9 is a diagram for explaining a change in the bandwidth of the reflected light due to the positional relationship between the alignment pattern and the beam waist according to the modification of the embodiment of the present invention. FIG. 10 is a diagram for explaining a change in the bandwidth of the reflected light due to the positional relationship between the alignment pattern and the beam waist according to the modification of the embodiment of the present invention. FIG. 11 is a diagram schematically showing the configuration of the wavelength selective optical switch. FIG. 12 is a plan view schematically showing the configuration of the MEMS mirror array chip.

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

<Configuration of wavelength selective optical switch>
As shown in FIG. 1, a wavelength selective optical switch including a deflection element according to the present embodiment includes a fiber array 1 that functions as an input / output optical system, a microlens array 2, a condensing lens 3, and a separation lens. The 4f optical system 4 functioning as a condensing optical system and the MEMS mirror array chip 5 functioning as the deflection element described above are arranged in this order along the Z-axis direction. In the present embodiment, the same components as those of the conventional wavelength selective optical switch described with reference to FIG. 11 are denoted by the same names and the same reference numerals, and detailed description thereof is omitted.

  In FIG. 1, the first lens 41 and the second lens 42 have a focal length of f1 [mm], the diffraction grating 43 has a dispersion capacity of dθ / dv [rad / GHz], and WDM signal light input from the input port 1a. When the frequency grid interval is νch [GHz], the beam waist of each wavelength (channel) that is demultiplexed by the diffraction grating 43 and imaged on the MEMS mirror array chip 5 is approximately f1 · tan (dθ / dv · νch) Align at [mm] pitch. Here, θ is a diffraction angle, and v is a wavelength. The mirror pitch Pch in the MEMS mirror array chip 5, that is, the interval between the MEMS mirror elements 52 described later, is set so as to match the pitch at which the beam waists of the respective channels are aligned. If the size of the beam waist on the focal plane on the condenser lens 3 side of the first lens 41 is a width Wx [μm] and a height Wy [μm], the second lens is obtained from the characteristics of the 4f optical system 4. The same beam waist shape is also reproduced on the focal plane of 42 MEMS mirror array chip 5 side.

≪Configuration of MEMS mirror array chip≫
As shown in FIG. 2, the mirror array chip 5 includes a base 51 having a substantially rectangular shape in a plan view, and a plurality of MEMS mirrors arranged in the base 51 and arranged at a mirror pitch Pch corresponding to the frequency in the X-axis direction. An element 52 and an alignment pattern 6 provided in one of these MEMS mirror elements 52 are provided.

  The base 51 is formed of a substantially rectangular substrate in plan view, such as an SOI (Silicon-On-Insulator) substrate. In such a base 51, a substantially rectangular opening in plan view extending in the X-axis direction is formed, and a mirror 52a (to be described later) of the MEMS mirror element 52 is arranged in the X-axis direction in the opening. Yes.

  The MEMS mirror element 52 includes a flexible spring (not shown), a mirror 52a connected to the base 51 by the spring, and an electrode (not shown) arranged opposite to the mirror 52a in the Z-axis direction. And. The mirror 52a is rotatable around the X axis and the Y axis by electrostatic attraction generated by applying a voltage to the electrode. In addition, a material having a high reflectance such as gold or aluminum is formed over the entire surface (hereinafter referred to as “upper surface”) of the mirror 52 a facing the second lens 42. Therefore, when the mirror 52a is rotated around the X axis, the optical axis of the reflected light that is incident on the mirror 52a and reflected by the mirror 52a changes in the Y axis direction. Thereby, selection of an output port can be realized. When the mirror 52a is rotated about the Y axis, the optical axis of the reflected light from the mirror 52a changes in the X axis direction. As a result, attenuation level control can be realized. In the present embodiment, the center of the mirror 52a of each MEMS mirror element 52 is located on a straight line along the X axis. The MEMS mirror element 52 is not limited to the above-described parallel plate type, and for example, a vertical comb structure can be applied. Further, the attenuation level is not limited to rotation around the Y axis, but may be controlled by rotation around the X axis.

  As shown in FIGS. 2 and 3, the alignment pattern 6 is provided on one of the plurality of MEMS mirror elements 52 formed on the MEMS mirror array chip 5, and is formed on the upper surface of the mirror 52a of the MEMS mirror element 52. Provided. The alignment pattern 6 is made of a material having a higher reflectance than the surrounding material such as gold or aluminum, and is formed in a diamond shape. The rhombus of the alignment pattern 6 is formed so that one of the diagonal lines is parallel to the X axis and the other is parallel to the Y axis, and is point-symmetric with respect to the intersection of these diagonal lines. The diagonal line parallel to the X axis is located on the same straight line as the center of the mirror 52a of each MEMS mirror element 52. A low reflection region 6a having a lower reflectance than the alignment pattern 6 is formed around the alignment pattern 6 on the upper surface of the mirror 52a. The low reflection region 6b is made of a material having a lower reflectance than the alignment pattern 6 such as Si, SiO2, Ti, Cr, for example.

  Such a MEMS mirror array chip 5 can be formed by a known MEMS technique. The alignment pattern 6 can be formed by a known photolithography technique. In the present embodiment, the alignment pattern 6 is formed by arranging a material having a high reflectance on the upper surface of the mirror 52a in a diamond shape. In this case, the alignment pattern 6 is composed of a region where the material having the high reflectance is arranged, and the low reflection region 6b is the base of the mirror 52a, that is, the base portion where the material having the high reflectance is not arranged. It is comprised from the area | region which 51 constituent materials exposed. In addition, the manufacturing method of the alignment pattern 6 is not limited to this, A various method can be applied freely. For example, the above-described material having a low reflectance may be formed in a predetermined pattern on the upper surface of the mirror 52a on which the material having a high reflectance such as gold or aluminum is formed. Alternatively, the pattern may be processed into a rhombus as described above by reactive ion etching or the like of one of the MEMS mirror elements 52, and the upper surface thereof may be covered with a material having a high reflectivity to form an alignment pattern. . In this case, since the alignment pattern 6 can be formed simultaneously with the other MEMS mirror elements 52 in the photolithography process, the center position on the X axis of the MEMS mirror element and the alignment pattern 6 can be matched with high accuracy.

<Alignment method>
Next, an alignment method between the MEMS mirror array chip 5 and the optical system will be described with reference to FIGS.

  First, in order to align the MEMS mirror array chip 5 in the X-axis direction and the Y-axis direction, as shown in FIG. 4, a light source 7 that outputs ASE light or light of a predetermined wavelength band to the input optical fiber 1a. The alignment stage 8 having a holder for holding the MEMS mirror array chip 5 and a stage for moving the holder in the X-axis, Y-axis, and Z-axis directions, and the spectrum of light output from the input optical fiber 1a. An optical spectrum analyzer 9 to be measured is prepared. If the light source has a desired wavelength band in addition to ASE light and can change the wavelength in synchronization with the frequency sweep speed of the optical spectrum analyzer, a variable wavelength light source is used. It may be. Similarly, a power sensor may be used instead of the optical spectrum analyzer.

  Next, in order to perform alignment in the X-axis direction, as shown in FIG. 5, the ASE light is input from the light source 7 to the wavelength selective optical switch as in the conventional case, and the spectrum of the reflected light from the MEMS mirror element 52 is calculated. Observation is performed by the optical spectrum analyzer 9 (step S1). At this time, the ASE light input from the light source 7 via the input port 1a is frequency-separated by the condensing lens 3 and the 4f optical system 4, and becomes a strip-like light parallel to the X-axis, and a plurality of MEMS mirror elements 52. Is irradiated. In the MEMS mirror element 52, the angle of the mirror 52a is controlled so that the irradiated light enters the input port 1a. Therefore, the band-like light is reflected by the MEMS mirror element 52, and this reflected light is coupled to the input port 1a through the 4f optical system 4 and the condenser lens 3, and is separated from the input light through the optical circulator or the like, and the optical spectrum. The optical spectrum shape is observed by the analyzer 9. The optical spectrum analyzer 9 observes a comb-like spectrum shape filtered by the frequency of light reflected by each MEMS mirror element 52 on a coordinate plane composed of a frequency axis and a light intensity axis. .

  When the comb-shaped spectrum is output, the center of the transmission band by each mirror element 52 is adjusted so as to match the center frequency of the signal channel assigned to each mirror element 52 while observing the spectrum as in the conventional case. The position of the MEMS mirror array chip 5 in the X-axis direction is adjusted by the center stage 8 (step S2). Thereby, the alignment of the MEMS mirror array chip 5 in the X-axis direction is completed. The alignment of the MEMS mirror array chip 5 in the Z-axis direction is performed by observing the spectral shape of the reflected light as described above, and widening the passband and reducing the loss so as to reduce the loss. This can be done by adjusting the position of the direction. By these operations, the mirror center position of each MEMS mirror element 52 and the center position of the beam waist formed by the light of the center frequency corresponding to each mirror through the 4f optical system 4 coincide with each other with respect to the X axis and the Z axis. It will be. In addition, since the alignment pattern 6 is disposed away from the MEMS mirror element 52 so that the center of the width having the extreme value of the alignment pattern coincides with the position corresponding to the optical frequency grid, similarly, The center position of the beam waist formed by the light having the center frequency corresponding to the alignment pattern 6 via the 4f optical system 4 is the same for the X axis and the Z axis.

  When alignment in the X-axis direction is completed, in order to perform alignment in the Y-axis direction, while continuously observing the shape of the reflected light spectrum with the optical spectrum analyzer 9, the frequency band width of the reflected light (hereinafter referred to as "bandwidth"). The position of the MEMS mirror array chip 5 in the Y-axis direction is adjusted by the aligning stage 8 so as to maximize (step S3). The principle of performing alignment in the Y-axis direction will be described with reference to FIG. FIG. 6 is a graph showing the positional relationship between the beam waist and the alignment pattern 6 when the MEMS mirror array chip 5 is moved in the Y-axis direction, and the light intensity and bandwidth of each wavelength at this time. Here, the bandwidth is defined as the frequency width of a region where a predetermined light intensity (for example, 0.5 dB) has decreased from the top of the transmission spectrum.

  The ASE light input via the input port 1a outputs a transmission spectrum to the optical spectrum analyzer in a form where the beam waist sweeps the wavelength of the mirror element 52 in the X-axis direction in each MEMS mirror element 52. When the MEMS mirror array chip 5 is moved in the Y-axis direction, the spectral shape of the light reflected by the alignment pattern 6 (6-1 to 6-3) in accordance with the positional relationship (6-1 to 6-3) of the beam waist irradiated to the alignment pattern 6 6-1 ′ to 6-3 ′) change. In the alignment pattern 6 according to the present embodiment, the area of the reflection region changes along the Y axis. For this reason, as the MEMS mirror array chip 5 moves in the Y-axis direction, the bandwidth (w1 to w3, 6-1 ″ to 6-3 ″) of the light reflected by the alignment pattern 6 changes. This is because the wavelength separation direction by the diffraction grating 43 is the X-axis direction, so that the ratio that the beam waist is clipped for each wavelength as the width of the alignment pattern 6 in the X-axis direction changes by moving the Y-axis. This is because the light intensity changes with respect to the frequency.

  As shown in FIG. 6, one diagonal line in the rhombus alignment pattern 6 is formed so as to be positioned on the same straight line as the center of the mirror 52 a of each MEMS mirror element 52. For this reason, when the bandwidth of the reflected light by the alignment pattern 6 becomes maximum (w2), that is, when one of the diagonal lines is located on the X axis, each MEMS mirror element 52 included in the MEMS mirror array chip 5 The center of the mirror 52a is also located on the X axis. Therefore, in the present embodiment, the MEMS mirror array chip 5 is moved in the Y-axis direction by the aligning stage 8, the bandwidth in the wavelength spectrum shape at this time is observed by the spectrum analyzer 9, and this bandwidth is maximized. Thus, by adjusting the position of the MEMS mirror array chip 5 in the Y-axis direction, the alignment of the MEMS mirror array chip 5 in the Y-axis direction can be realized.

The relationship between the amount of shift in the Y-axis direction and the change in bandwidth depends on the shape of the alignment pattern 6 and the profile of the light beam applied to the alignment pattern 6. In the present embodiment, the alignment pattern 6 is formed in a diamond shape, and the extreme value of the area of the reflection region of the alignment pattern 6 exists on the X axis, and the bandwidth thereof is between the beam waist and the alignment pattern. Extreme value when center position matches. Since the beam profile of the beam waist irradiated to the alignment pattern 6 is elliptical, when the MEMS mirror array chip 5 is moved in the Y-axis direction, the change in the transmission spectrum shape with respect to the change in the area of the reflection region of the alignment pattern 6 Becomes steep. For this reason, as shown by the curve indicated by α in FIG. 6, the change in bandwidth also becomes steep. Specifically, the maximum is when one diagonal line of the alignment pattern 6 is located on the X-axis, and as the deviation in the Y-axis direction increases, the two convex downward from the maximum to the positive and negative sides in the Y-axis direction. It changes to a so-called skirt-spreading shape that decreases like a next function. As described above, since the bandwidth changes sharply toward the local maximum value, the local maximum value can be easily identified. As a result, more accurate alignment can be performed for the position of the MEMS mirror array chip 5 in the Y-axis direction. Can be realized.
Since the intensity of the reflected light depends on the beam shape and the alignment pattern shape, the area of the reflection surface of the alignment pattern 6 irradiated by the beam waist becomes conspicuous as the MEMS mirror array chip 5 moves in the Y-axis direction. In such a case, the light intensity at the top of the transmission spectrum may also change. Also in this case, it is possible to detect the extreme value of the bandwidth regardless of the change in the light intensity.

  As described above, according to the present embodiment, the width (length) of the wavelength separation direction changes as the alignment pattern 6 moves away from the axis parallel to the X axis, that is, the length in the wavelength separation direction. When the input light is irradiated onto the alignment pattern 6, the bandwidth of the reflected light by the alignment pattern 6 is not displaced from the Y-axis by the MEMS mirror array chip 5. It becomes possible to make it maximum. Thereby, the alignment in the Y-axis direction of the MEMS mirror array chip 5 can be performed only by adjusting the position of the MEMS mirror array chip 5 in the Y-axis direction based on the bandwidth of the reflected light.

  In the present embodiment, the case where the rhombus alignment pattern 6 is provided has been described as an example. However, similarly to the alignment pattern 6, when the light is positioned on the X axis, the alignment pattern and the reflected light around the alignment pattern are reflected. If the alignment pattern has a peak bandwidth, the shape is not limited to a rhombus and can be set as appropriate. In other words, if the width of the wavelength separation direction changes with distance from a predetermined axis parallel to the X-axis direction, and the shape has an extreme value in the width of the wavelength separation direction on the first axis, the shape of the alignment pattern Can be set freely as appropriate. The modification is shown below.

<First Modification>
The alignment pattern 10 shown in FIG. 7 is made of a material having a lower reflectance than the surroundings, and is formed in a diamond shape. One diagonal line in the rhombus alignment pattern 10 is formed in parallel to the X axis and is positioned on the same straight line as the center of the mirror 52 a of each MEMS mirror element 52. In addition, a rectangular high reflection region 10 a made of a material having a higher reflectance than the alignment pattern 10 is formed around the alignment pattern 10. Even by adopting such a configuration, when the position of the MEMS mirror array chip 5 in the Y-axis direction is changed, the spectral shape of the reflected light changes according to the positional relationship of the beam waist irradiated to the alignment pattern 10. . At this time, the bandwidth of the reflected light also changes as the length of the beam waist irradiated to the alignment pattern 10 changes in the X-axis direction.
Here, the bandwidth is defined as the frequency width of a region where a predetermined light intensity (for example, 0.5 dB) has decreased from the top of the transmission spectrum. In the case of a spectral shape in which a depression is formed at the center of the transmission band as in this embodiment, the band obtained by adding the frequency width of the region where the predetermined light intensity has decreased from the top of the left and right flat portions Width.

For example, when the minor axis of the beam waist B is positioned on a diagonal line parallel to the X axis in the alignment pattern 10 formed in a diamond shape, only the outer edge (region 10-2) of the beam waist B becomes the highly reflective region 10a. Irradiated. For this reason, the spectrum shape 10-2 ′ of the reflected light by the highly reflective region 10a has two light intensity that is low in the central portion in the frequency band of the beam waist B, and the light intensity is detected on both sides of the central portion. It becomes a mountain-shaped profile. At this time, since the length in the X-axis direction of the beam waist B irradiated to the highly reflective region 10a is minimized, the bandwidth of the reflected light is also minimized.
On the other hand, when the short axis of the beam waist B is not located on the diagonal line parallel to the X axis in the alignment pattern 10 formed in a diamond shape, the beam waist B is also irradiated to the highly reflective region 10a at portions other than the outer edge portion. (Regions 10-1 and 10-3). For this reason, in the spectral shapes 10-1 ′ and 10-3 ′ of the reflected light, the light intensity is detected closer to the center in the frequency band of the beam waist B than in the case of the spectral shape 10-2 ′. . At this time, since the length in the X-axis direction of the beam waist B irradiated to the highly reflective region 10a is larger than that in the region 10-2 described above, the bandwidth of the reflected light is also the region 10-2. It becomes a larger value than the case of.

  Therefore, the bandwidth of the reflected light by the high reflection region 10a measured by the optical spectrum analyzer 9 is when one diagonal line of the alignment pattern 10 is located on the X axis as shown by the curve indicated by symbol β in FIG. It becomes a minimum, and increases from this minimum value to a positive and negative side in the Y-axis direction as a quadratic function convex upward. In other words, it changes so as to draw an upside down curve with respect to the bandwidth of the reflected light by the alignment pattern 6 indicated by the symbol α in FIG. Since the bandwidth changes sharply toward the minimum value in this way, the minimum value can be easily identified, and as a result, more accurate alignment is realized with respect to the position of the MEMS mirror array chip 5 in the Y-axis direction. can do.

<Second Modification>
Further, the alignment pattern 11 shown in FIG. 8 is made of a material having a higher reflectance than the surroundings, and is formed in a pentagon. Around the alignment pattern 11, a rectangular low reflection region 11 a made of a material having a reflectance lower than that of the alignment pattern 11 is formed. When such a configuration is adopted, when the position of the MEMS mirror array chip 5 in the Y-axis direction is changed, the bandwidth of the reflected light by the alignment pattern 11 measured by the optical spectrum analyzer 9 is represented by the symbol γ in FIG. As shown by the curve shown, the beam waist irradiated to the alignment pattern 11 is maximized when the length in the X-axis direction becomes a maximum, and as the deviation in the Y-axis direction increases, the positive and negative in the Y-axis direction from the maximum respectively. It will decrease asymmetrically on the side. In this way, even if the alignment pattern is symmetric with respect to the X axis, the bandwidth sharpens toward the maximum and changes asymmetrically in the Y axis direction, so that the maximum can be easily identified. As a result, more accurate alignment can be realized with respect to the position of the MEMS mirror array chip 5 in the Y-axis direction.

<Third Modification>
Moreover, the alignment pattern 12 shown in FIG. 9 is made of a material having a higher reflectance than the surroundings, and is formed in a semicircular or kamaboko shape. Around the alignment pattern 11, a rectangular low reflection region 12 a made of a material having a lower reflectance than the alignment pattern 12 is formed. When such a configuration is adopted, when the position of the MEMS mirror array chip 5 in the Y-axis direction is changed, the bandwidth of the reflected light by the alignment pattern 12 measured by the optical spectrum analyzer 9 is represented by the symbol γ in FIG. As shown by the curve shown in the figure, the beam waist irradiated to the alignment pattern 12 has a maximum when the length in the X-axis direction is maximized, and the deviation from the maximum in the Y-axis direction increases and decreases in the positive and negative directions in the Y-axis direction. It will decrease asymmetrically to the side. Even if the shape is asymmetric with respect to the Y axis, the bandwidth changes sharply toward the maximum, so that the maximum can be easily identified. As a result, the Y axis of the MEMS mirror array chip 5 can be identified. More accurate alignment with respect to the position in the direction can be realized.

<Fourth Modification>
Further, the alignment pattern 13 shown in FIG. 10 is made of a material having a higher reflectance than the surroundings, and is formed in a drum shape with a substantially central portion in the Y-axis direction being constricted. The drum shape is formed of, for example, a shape obtained by combining two triangles that are arranged such that the bases are parallel to each other and the vertices that do not constitute the base or the vicinity of the vertices are connected. Around the alignment pattern 13, a substantially triangular low reflection region 13 a made of a material having a lower reflectance than that of the alignment pattern 13 is formed. When such a configuration is adopted, when the position of the MEMS mirror array chip 5 in the Y-axis direction is changed, the bandwidth of the reflected light by the alignment pattern 13 measured by the optical spectrum analyzer 9 is represented by the symbol ε in FIG. As shown by the curve shown in the figure, the beam waist irradiated to the alignment pattern 13 is minimized when the length in the X-axis direction is minimal, and as the deviation in the Y-axis direction increases, the minimum and positive values in the Y-axis direction are increased from the minimum. Will increase to the side. In this manner, even when the drum shape is formed, the bandwidth changes sharply toward the minimum, so that the minimum can be identified. As a result, the position of the MEMS mirror array chip 5 in the Y-axis direction can be determined. More accurate alignment can be realized.

  In the alignment patterns 10 to 13 described above, when the minor axis of the beam waist passes through the center of the mirror 52a on which each alignment pattern is formed, the bandwidth of the reflected light by the alignment pattern is maximized or minimized. Needless to say, it is formed. At this time, the center of the mirror 52a of each MEMS mirror element 52 included in the MEMS mirror array chip 5 is formed so as to be located on the same straight line as the center of the mirror 52a on which the alignment patterns 10 to 13 are formed.

  In the present embodiment, the case where the alignment pattern 6 is provided in the MEMS mirror element 52 at one end has been described as an example. However, if the MEMS mirror element 52 is provided in the MEMS mirror array chip 5, the alignment pattern 6 is provided. The position is not limited to the MEMS mirror element 52 at the end, and can be freely set as appropriate.

  In the present embodiment, the case where the alignment pattern is provided in the MEMS mirror element 52 has been described as an example. However, the position where the alignment pattern is provided is not limited to the MEMS mirror element 52. For example, the base portion of the MEMS mirror array chip 5 is provided. 51 may be provided.

  Further, in the present embodiment, the case where the surface of the mirror 52a is provided with an alignment pattern composed of a high reflection region or a low reflection region and a high reflection region or a low reflection region provided around the surface is described as an example. As long as a bandwidth peak is formed on the Y-axis, the configuration of the alignment pattern and the like is not limited to such a configuration, and can be freely set as appropriate. For example, the outer shape of the mirror 52a, the entire surface of which is a highly reflective region, may be formed into a rhombus or a pentagon as described above. Further, an opening may be provided in the mirror 52a, and this opening may be used as a low reflection region. However, when the mirror 52a itself is processed, the area as a parallel plate is reduced, so that the generated electrostatic attractive force is reduced. If the spring constant (hardness) of the spring that supports the mirror 52a is the same as that when the outer shape is not processed, the mirror 52a cannot be rotated unless the mirror drive voltage is increased. This restricts the maximum rotation angle of the mirror 52a and makes it difficult to maintain the linearity of the drive voltage and the rotation angle, making it difficult to perform precise angle control. For this reason, when the alignment pattern is formed by processing the outer shape of the mirror 52a itself, the area of the mirror 52a is significantly reduced compared to before the processing, as in the second and third modifications. It is desirable not to design.

  In the present embodiment, the case where the present invention is applied to the MEMS mirror array chip 5 has been described as an example. However, the present embodiment can also be applied to a WSS using other micro switch arrays such as a transmission type and a reflection type liquid crystal switch array. it can.

  In the present embodiment, the MEMS mirror array chip 5 in which the mirror elements 52 are arranged one-dimensionally has been described. Needless to say, the present invention can also be applied to a MEMS mirror array arranged two-dimensionally. In this case, the same effect as that of the present embodiment can be realized by disposing the alignment pattern described above at any position of the channel demultiplexed by the diffraction grating.

  Furthermore, in the present embodiment, the case where the present invention is applied to a wavelength selective optical switch has been described as an example. However, the present invention can be freely applied as long as it is an element that deflects wavelength-separated input light or an optical system including this element. Needless to say, you can. Further, the element can be applied regardless of whether or not the element can be rotated around a predetermined axis.

  The present invention can be applied to an element that deflects wavelength-separated input light and various optical systems including this element.

  DESCRIPTION OF SYMBOLS 1 ... Fiber array, 1a ... Input port, 1b ... Output port, 2 ... Micro lens array, 3 ... Condensing lens, 4 ... 4f optical system, 5 ... MEMS mirror array chip, 6, 10-13 ... Alignment pattern, 6a , 11a, 12a, 13a ... low reflection area, 10a ... high reflection area, 6-1 to 6-3, 10-1 to 10-3 ... area, 6-1 'to 6-3', 10-1 'to 10-3 '... spectrum shape, 6-1 "to 6-3" ... bandwidth, 7 ... broadband light source, 8 ... alignment stage, 9 ... spectrum analyzer, 41 ... first lens, 42 ... second lens, 43 ... Diffraction grating, 51 ... Base, 52 ... MEMS mirror element, 52a ... Mirror.

Claims (6)

A deflection element for deflecting input light separated according to wavelength,
From a predetermined first axis having a reflectance different from the surroundings and parallel to the wavelength separation direction of the input light, along a second axis orthogonal to the first axis and intersecting the optical axis of the input light A deflection element comprising: an alignment pattern having a shape in which the width in the wavelength separation direction changes with distance from the first axis and has an extreme value of the width in the wavelength separation direction on the first axis. The deflection element according to claim 1, wherein the alignment pattern has a point-symmetric shape with respect to an intersection of the first axis and the second axis.   3. The deflecting element according to claim 2, wherein the alignment pattern has a rhombus shape in which one of diagonal lines is parallel to the first axis and the other is parallel to the second axis.   The deflection element according to claim 2, wherein the alignment pattern has a drum-shaped shape in which a width in the wavelength separation direction at a central portion in the direction of the second axis is an extreme value. 5. The alignment pattern according to claim 1, wherein the alignment pattern is arranged such that a center of a width corresponding to the extreme value of the alignment pattern coincides with a position corresponding to the optical frequency grid. The deflecting element according to 1. A deflection element alignment method for deflecting input light separated according to wavelength,
For an alignment pattern provided on the deflecting element, having a different reflectance from the surroundings, and having a shape in which the width in the wavelength separation direction changes as it moves away from a predetermined first axis parallel to the wavelength separation direction of the input light. A first step of irradiating the wavelength-separated light in the first axial direction;
The width of the frequency band of the reflected light from the alignment pattern is measured, and the width in the direction of the second axis intersecting with the optical axis of the input light is orthogonal to the first axis so that the width becomes an extreme value. And a second step of adjusting the position of the deflection element.

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