Fabry-perot interference filter

Abstract

Thise Fabry-Perot interference filter comprises a fixed layer including a fixed mirror part, and a movable layer including a movable mirror part facing the fixed mirror part, with a gap therebetween. The movable mirror portion includes a first portion corresponding to a light transmission region, and a second portion surrounding the first portion when viewed from the direction in which the fixed mirror portion and the movable mirror portion face each other. The area of a region in which the first portion is disposed and which corresponds to the light transmission region is larger than the area of an annular region in which the second portion is disposed and which surrounds the light transmission region. The distance between the outer edge of the first portion and the outer edge of the gap is greater than the thickness of the gap.

Description

Fabry-Perot interference filter

[0001] The present disclosure relates to Fabry-Perot interference filters.

[0002] A Fabry-Perot interference filter is known that includes a fixed layer including a fixed mirror portion and a movable layer including a movable mirror portion facing the fixed mirror portion via an air gap, in which the distance between the fixed mirror portion and the movable mirror portion is adjusted by electrostatic force (see, for example, Patent Document 1).

[0003] JP 2023-45859 A JP 2004-205973 A

[0004] In the Fabry-Perot interference filter described above, it is sometimes important to widen the light transmission area for transmitting light having a desired wavelength. However, simply increasing the size of the Fabry-Perot interference filter may result in the transmission of noise light, which may result in a deterioration of the signal-to-noise ratio.

[0005] Therefore, an object of the present disclosure is to provide a Fabry-Perot interference filter that can appropriately ensure a light transmission region for transmitting light having a desired wavelength.

[0006] A Fabry-Perot interference filter according to one aspect of the present disclosure is [1] "a Fabry-Perot interference filter comprising: a fixed layer including a fixed mirror portion; and a movable layer including a movable mirror portion facing the fixed mirror portion across a gap, wherein the movable mirror portion includes a first portion corresponding to a light transmission region and a second portion surrounding the first portion when viewed from a direction in which the fixed mirror portion and the movable mirror portion face each other; the movable mirror portion is configured such that a distance between the fixed mirror portion and the first portion in the light transmission region is adjusted by deformation of at least a part of the second portion due to electrostatic force; when viewed from the direction, an area of ​​a region in which the first portion is disposed and which corresponds to the light transmission region is larger than an area of ​​an annular region in which the second portion is disposed and which surrounds the light transmission region when viewed from the direction; and a distance between an outer edge of the first portion and an outer edge of the gap when viewed from the direction is larger than a thickness of the gap in the direction."

[0007] In the above-mentioned Fabry-Perot interference filter, when viewed from the direction in which the fixed mirror section and the movable mirror section face each other, the area in which the first section is disposed and which corresponds to the light-transmitting region is larger than the area in which the second section, which deforms due to electrostatic force, is disposed and which surrounds the light-transmitting region. This ensures a sufficiently large light-transmitting region for transmitting light having a desired wavelength. Furthermore, in the above-mentioned Fabry-Perot interference filter, the distance between the outer edge of the first section and the outer edge of the gap, when viewed from the direction in which the fixed mirror section and the movable mirror section face each other, is larger than the thickness of the gap in the direction in which the fixed mirror section and the movable mirror section face each other. This ensures a sufficient width for the second section, which deforms due to electrostatic force, thereby improving the parallelism of the first section with respect to the fixed mirror section and suppressing the transmission of noise light. Therefore, the above-mentioned Fabry-Perot interference filter ensures an appropriate light-transmitting region for transmitting light having a desired wavelength.

[0008] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [2] "the Fabry-Perot interference filter according to the above [1], further comprising a light-shielding layer having an opening formed therein corresponding to the light-transmitting region." This Fabry-Perot interference filter can suppress the emission of light that has passed through the second portion that deforms due to electrostatic force.

[0009] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [3] "the Fabry-Perot interference filter according to the above [1] or [2], wherein the second portion includes an inner portion surrounding the first portion when viewed from the direction and an outer portion surrounding the inner portion when viewed from the direction, and the inner portion is formed with at least one of a plurality of grooves surrounding the first portion when viewed from the direction and a plurality of through holes opening on both sides in the direction." With this Fabry-Perot interference filter, it is possible to make the second portion more deformable, and further improve the parallelism of the first portion with respect to the fixed mirror portion.

[0010] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [4] "the Fabry-Perot interference filter according to the above [3], in which the width of the outer portion when viewed from the direction is larger than the width of the inner portion when viewed from the direction." With this Fabry-Perot interference filter, it is possible to make the second portion more easily deformable, and to further improve the parallelism of the first portion with respect to the fixed mirror portion.

[0011] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [5] "the Fabry-Perot interference filter according to the above [3] or [4], wherein the width of the outer portion when viewed from the direction is greater than the thickness of the gap in the direction." With this Fabry-Perot interference filter, the second portion can be made more easily deformed, and the parallelism of the first portion with respect to the fixed mirror portion can be further improved.

[0012] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [6] "the Fabry-Perot interference filter according to any one of the above [1] to [5], wherein the area of ​​the gap when viewed from the direction is larger than half the area of ​​the fixed layer when viewed from the direction and larger than half the area of ​​the movable layer when viewed from the direction." With this Fabry-Perot interference filter, it is possible to ensure a light transmission region that is sufficiently large to transmit light having a desired wavelength, while preventing the Fabry-Perot interference filter from becoming too large.

[0013] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [7] "the Fabry-Perot interference filter according to any one of the above [1] to [6], further comprising a first terminal and a second terminal, the fixed layer further including a fixed electrode electrically connected to the first terminal, the movable layer further including a movable electrode electrically connected to the second terminal, and at least one of the distance between the outer edge of the gap and the outer edge of the first terminal when viewed from the direction and the distance between the outer edge of the gap and the outer edge of the second terminal when viewed from the direction is greater than the distance between the outer edge of the first portion and the outer edge of the gap when viewed from the direction." According to this Fabry-Perot interference filter, when an external force acts on the first terminal, if the distance between the outer edge of the gap and the outer edge of the first terminal is greater than the distance between the outer edge of the first part and the outer edge of the gap, the external force is less likely to reach the movable mirror part; and when the distance between the outer edge of the gap and the outer edge of the second terminal is greater than the distance between the outer edge of the first part and the outer edge of the gap, the external force is less likely to reach the movable mirror part when an external force acts on the second terminal, thereby preventing damage to the movable mirror part that faces the fixed mirror part across the gap.

[0014] A Fabry-Perot interference filter according to one aspect of the present disclosure may be [8] "the Fabry-Perot interference filter according to any one of [1] to [7] above, in which, when viewed from the direction, the outer edge of the first portion and the outer edge of the gap have a circular shape with the same center." This Fabry-Perot interference filter can more appropriately ensure a light transmission region for transmitting light having a desired wavelength.

[0015] According to the present disclosure, it is possible to provide a Fabry-Perot interference filter that can appropriately ensure a light transmission region for transmitting light having a desired wavelength.

[0016] Fig. 1 is a plan view of a Fabry-Perot interference filter according to one embodiment. Fig. 2 is a cross-sectional view of the Fabry-Perot interference filter taken along line II-II in Fig. 1. Fig. 3 is an enlarged view of a portion of the Fabry-Perot interference filter shown in Fig. 2.

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [Configuration of Fabry-Perot interference filter]

[0018] 1 and 2, the Fabry-Perot interference filter 1 has a light-transmitting region 1a. As an example, the Fabry-Perot interference filter 1 has a square plate shape with a straight line L as its center line, and the light-transmitting region 1a has a cylindrical shape with the straight line L as its center line. The Fabry-Perot interference filter 1 includes a fixed mirror portion 11 and a movable mirror portion 12. The movable mirror portion 12 faces the fixed mirror portion 11 in the direction α with a gap S therebetween.

[0019] The Fabry-Perot interference filter 1 includes a substrate 21. An antireflection layer 31, a first stack (fixed layer) 32, an intermediate layer 33, and a second stack (movable layer) 34 are stacked in this order on a surface 21a on one side of the substrate 21. The substrate 21 is, for example, a square plate with a straight line L as its center line. The substrate 21 is made of, for example, silicon, quartz, glass, or the like. When the substrate 21 is made of silicon, the antireflection layer 31 and the intermediate layer 33 are made of, for example, silicon oxide, or the like. The thickness of the intermediate layer 33 is, for example, an integral multiple of ½ the design center wavelength. The intermediate layer 33 is formed in a frame shape and defines a gap S between the first stack 32 and the second stack 34. In this embodiment, the shape of the gap S is a cylinder with the straight line L as its center line. Note that the thickness of the intermediate layer 33 may be greater than an integral multiple of ½ the design center wavelength, if necessary.

[0020] The first stack 32 includes a fixed mirror section 11. The fixed mirror section 11 is a portion of the first stack 32 that overlaps with the gap S when viewed from the direction α. ​​The fixed mirror section 11 is supported on the substrate 21 via an anti-reflection layer 31. As an example, the first stack 32 is configured by alternately stacking multiple polysilicon layers and multiple silicon nitride layers. The optical thickness of each layer that configures the fixed mirror section 11 is, for example, an integral multiple of ¼ of the design central wavelength. Note that a silicon oxide layer may be used instead of the silicon nitride layer.

[0021] The second stack 34 includes a movable mirror section 12. The movable mirror section 12 is a portion of the second stack 34 that overlaps with the gap S when viewed from the direction α. ​​The movable mirror section 12 is supported on the substrate 21 via an anti-reflection layer 31, the first stack 32, and an intermediate layer 33. As an example, the second stack 34 is configured by alternately stacking multiple polysilicon layers and multiple silicon nitride layers. The optical thickness of each layer that configures the movable mirror section 12 is, for example, an integer multiple of ¼ of the design central wavelength. Note that a silicon oxide layer may be used instead of the silicon nitride layer.

[0022] A fixed electrode 13 and a compensation electrode 14 are formed on the fixed mirror portion 11. That is, the first stack 32 includes the fixed electrode 13 and the compensation electrode 14. The fixed electrode 13 surrounds the light-transmitting region 1a when viewed from direction α. ​​The shape of the fixed electrode 13 when viewed from direction α is, for example, annular. The compensation electrode 14 corresponds to the light-transmitting region 1a. The shape of the compensation electrode 14 when viewed from direction α is, for example, circular, and is substantially the same as the shape of the light-transmitting region 1a when viewed from direction α. ​​As an example, the fixed electrode 13 and the compensation electrode 14 are each formed by doping impurities into a portion of the same polysilicon layer that constitutes the first stack 32 to reduce the resistance of that portion.

[0023] A movable electrode 15 is formed on the movable mirror portion 12. That is, the second stack 34 includes the movable electrode 15. The movable electrode 15 faces the fixed electrode 13 and the compensation electrode 14 in the direction α with a gap S interposed therebetween. The shape of the compensation electrode 14 when viewed from the direction α is, for example, circular. As one example, the movable electrode 15 is formed by doping impurities into a portion of the polysilicon layer that constitutes the second stack 34 to reduce the resistance of that portion.

[0024] The Fabry-Perot interference filter 1 includes a pair of first terminals 16 and a pair of second terminals 17. The pair of first terminals 16 and the pair of second terminals 17 are arranged at corners of the substrate 21 so that the first terminals 16 and the second terminals 17 are positioned diagonally when viewed from the direction α. ​​Each first terminal 16 is arranged in a recess extending from a surface 34a of the second stack 34 opposite the substrate 21 to a surface 32a of the first stack 32 opposite the substrate 21. Each first terminal 16 is electrically connected to the fixed electrode 13 via a wiring 13a. Each second terminal 17 is arranged in a recess extending from the surface 34a of the second stack 34 to the intermediate layer 33. Each second terminal 17 is electrically connected to the compensation electrode 14 via a wiring 14a and to the movable electrode 15 via a wiring 15a.

[0025] A pair of trenches 18a are formed in the first stack 32. Each trench 18a surrounds a portion of the wiring 14a extending from each second terminal 17 along the direction α. ​​Each trench 18a electrically insulates the fixed electrode 13 from the wiring 14a. A plurality of trenches 18b are formed in the first stack 32. The plurality of trenches 18b surround the compensation electrode 14 inside the fixed electrode 13. The plurality of trenches 18b are arranged, for example, concentrically. The plurality of trenches 18b electrically insulate the fixed electrode 13 from the compensation electrode 14. A pair of trenches 19 are formed in the second stack 34. Each trench 19 surrounds a corresponding first terminal 16. Each trench 19 electrically insulates the corresponding first terminal 16 from the movable electrode 15. The regions within each of the trenches 18a, 18b, and 19 may be made of an insulating material or may be voids.

[0026] An antireflection layer 41, a third stacked body 42, an intermediate layer 43, and a fourth stacked body 44 are stacked in this order on the surface 21b on the other side of the substrate 21. The antireflection layer 41 and the intermediate layer 43 have the same configurations as the antireflection layer 31 and the intermediate layer 33, respectively. The third stacked body 42 and the fourth stacked body 44 have stacked structures symmetrical to the first stacked body 32 and the second stacked body 34, respectively, with respect to the substrate 21. The antireflection layer 41, the third stacked body 42, the intermediate layer 43, and the fourth stacked body 44 have the function of suppressing warpage of the substrate 21.

[0027] Openings 40a are formed in the third stack 42, the intermediate layer 43, and the fourth stack 44. The openings 40a correspond to the light-transmitting regions 1a. The shape of the openings 40a when viewed from the direction α is, for example, circular and is substantially the same as the shape of the light-transmitting regions 1a when viewed from the direction α. ​​The openings 40a open on the side opposite the substrate 21. The bottom surfaces of the openings 40a reach the anti-reflection layer 41. A light-shielding layer 45 is stacked on the surface of the fourth stack 44 opposite the substrate 21. An opening 45a is formed in the light-shielding layer 45. The opening 45a corresponds to the light-transmitting regions 1a. The material of the light-shielding layer 45 is, for example, aluminum. A protective layer 46 is formed on the surface of the light-shielding layer 45 opposite the substrate 21 and on the inner surfaces of the openings 45a and 40a. The material of the protective layer 46 is, for example, aluminum oxide. It should be noted that by setting the thickness of the protective layer 46 to 100 nm or less (preferably, about 30 nm), the optical influence of the protective layer 46 can be ignored. [Configuration of the Movable Mirror Portion]

[0028] The movable mirror portion 12 includes a first portion 121 and a second portion 122. The first portion 121 corresponds to the light-transmitting region 1a. The shape of the first portion 121 when viewed from the direction α is, for example, circular, and is substantially the same as the shape of the light-transmitting region 1a when viewed from the direction α. ​​The second portion 122 surrounds the first portion 121 when viewed from the direction α. ​​The shape of the second portion 122 when viewed from the direction α is, for example, annular. In this embodiment, the entire second portion 122 is located outside the opening 45a of the light-shielding layer 45 when viewed from the direction α.

[0029] The second portion 122 includes an inner portion 122a and an outer portion 122b. The inner portion 122a surrounds the first portion 121 when viewed from the direction α. ​​The shape of the inner portion 122a when viewed from the direction α is, for example, an annular shape. The outer portion 122b surrounds the inner portion 122a when viewed from the direction α. ​​The shape of the outer portion 122b when viewed from the direction α is, for example, an annular shape.

[0030] The movable mirror unit 12 is configured so that the distance between the fixed mirror unit 11 and the first unit 121 in the light transmission region 1a is adjusted by at least a portion of the second unit 122 being deformed by electrostatic force. Specifically, as shown in FIG. 3 , a plurality of grooves 35 and a plurality of through holes 36 are formed in the inner portion 122a of the second unit 122. The plurality of grooves 35 surround the first unit 121 when viewed from the direction α. ​​The plurality of grooves 35 are, for example, arranged concentrically and face the plurality of trenches 18 in the direction α. ​​Each groove 35 opens on the side opposite the void S and is formed by the plurality of polysilicon layers and the plurality of silicon nitride layers constituting the first stack 32 partially recessing toward the void S. As an example, the width of each groove 35 is 0.1 to 100 μm, and the distance between adjacent grooves 35 is 1 to 250 μm. Note that the grooves 35 are not limited to extending continuously, but may extend intermittently. Adjacent grooves 35 may be partially connected.

[0031] Each through hole 36 is open on both sides in the direction α. ​​That is, each through hole 36 is open on the void S side and the opposite side. At least a portion of the multiple through holes 36 is located between adjacent grooves 35. When viewed from the direction α, each through hole 36 has, for example, a circular shape. As an example, the diameter of each through hole 36 is 1 to 10 μm, and the distance between adjacent through holes 36 is 10 to 100 μm. Note that the multiple through holes 36 are formed not only in the inner portion 122a but also throughout the entire movable mirror section 12 (not shown in FIGS. 1 and 2). The multiple through holes 36 are formed uniformly dispersed to such an extent that they do not substantially affect the function of the movable mirror section 12. The multiple through holes 36 are used when forming the void S by removing a portion of the intermediate layer 33 by etching. [Operation of the Fabry-Perot Interference Filter]

[0032] In the Fabry-Perot interference filter 1, when a voltage is applied to the fixed electrode 13 and the movable electrode 15 via the first terminal 16 and the second terminal 17, causing a potential difference between the fixed electrode 13 and the movable electrode 15, an electrostatic force corresponding to the potential difference is generated between the fixed electrode 13 and the movable electrode 15. This causes the second portion 122 of the movable mirror portion 12 to deform, attracting the first portion 121 to the fixed mirror portion 11, and adjusting the distance between the fixed mirror portion 11 and the first portion 121 in the light transmission region 1a. At this time, the compensation electrode 14 facing the first portion 121 in the direction α has the same potential as the movable electrode 15, so that the first portion 121 of the movable mirror portion 12 is kept flat in the light transmission region 1a.

[0033] As described above, in the Fabry-Perot interference filter 1, the distance between the fixed mirror portion 11 and the first portion 121 of the movable mirror portion 12 is variable. Here, the wavelength of light transmitted through the light transmission region 1a of the Fabry-Perot interference filter 1 depends on the distance between the fixed mirror portion 11 and the first portion 121 of the movable mirror portion 12. Therefore, by adjusting the voltage applied to the fixed electrode 13 and the movable electrode 15 (the potential difference generated between the fixed electrode 13 and the movable electrode 15), it is possible to select the wavelength of light transmitted through the Fabry-Perot interference filter 1. Note that light may be transmitted through the light transmission region 1a from the movable mirror portion 12 side to the opening 40a side, or may be transmitted through the light transmission region 1a from the opening 40a side to the movable mirror portion 12 side. [Size of Fabry-Perot Interference Filter]

[0034] As shown in FIG. 1 , the area of ​​the region where the first portion 121 is disposed and corresponds to the light-transmitting region 1a when viewed from the direction α is larger than the area of ​​the annular region where the second portion 122 is disposed and surrounds the light-transmitting region 1a when viewed from the direction α. ​​The area of ​​the gap S when viewed from the direction α is larger than half the area of ​​the first stack 32 when viewed from the direction α and is also larger than half the area of ​​the second stack 34 when viewed from the direction α. ​​In this embodiment, the "area of ​​the region where the first portion 121 is disposed and corresponds to the light-transmitting region 1a when viewed from the direction α" is the total area of ​​the "first portion 121" and the "plurality of through holes 36 formed in the first portion 121." Furthermore, the "area of ​​the annular region where the second portion 122 is disposed and surrounds the light-transmitting region 1a when viewed from the direction α" is the total area of ​​the "second portion 122" and the "plurality of through holes 36 formed in the second portion 122." In addition, when the plurality of second portions 122 surround the first portion 121 when viewed from the direction α, the "area of ​​the annular region in which the second portions 122 are arranged and which surrounds the light-transmitting region 1a when viewed from the direction α" is the total area of ​​the "plurality of second portions 122" and the "region (gap) between adjacent second portions 122." The "area of ​​the annular region in which the second portions 122 are arranged and which surrounds the light-transmitting region 1a when viewed from the direction α" is also the value obtained by subtracting the "area of ​​the region in which the first portion 121 is arranged and which corresponds to the light-transmitting region 1a when viewed from the direction α" from the "area of ​​the circle circumscribing the second portions 122 when viewed from the direction α."

[0035] 1 and 2 , the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S when viewed from the direction α is greater than the thickness T of the gap S in the direction α. ​​The width C of the outer portion 122b when viewed from the direction α is greater than the width B of the inner portion 122a when viewed from the direction α. ​​The width C of the outer portion 122b when viewed from the direction α is greater than the thickness T of the gap S in the direction α.

[0036] The distance A is the distance between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S in a cross section including the straight line L. If the distance is not constant in any cross section including the straight line L, the distance A refers to the minimum value of the distance. The thickness T is the distance between the surface of the fixed mirror portion 11 facing the gap S and the surface of the first portion 121 of the movable mirror portion 12 facing the gap S in a state where no voltage is applied to the fixed electrode 13 and the movable electrode 15. For example, if no stress or distortion occurs in the movable mirror portion 12, the thickness T is equal to the thickness of the intermediate layer 33. However, if stress or distortion occurs in the movable mirror portion 12, the thickness T becomes larger or smaller than the thickness of the intermediate layer 33. The width B is the width of the inner portion 122a in a cross section including the straight line L. If the width is not constant in any cross section including the straight line L, the width B refers to the maximum value of the width. The width C is the "width of the outer portion 122b" in a cross section including the straight line L, and if the width is not constant in any cross section including the straight line L, it means the minimum value thereof.

[0037] In this embodiment, when viewed from the direction α, the outer edge 121E of the first portion 121 and the outer edge S1 of the void S have circular shapes with the same center. Therefore, in any cross section including the straight line L, the distance A is approximately constant and greater than the thickness T. Similarly, in any cross section including the straight line L, the width C is approximately constant and greater than the thickness T. Note that in this embodiment, the outer edge S1 of the void S when viewed from the direction α coincides with the outer edge 122E of the second portion 122 when viewed from the direction α.

[0038] 1 , the distance D1 between the outer edge S1 of the gap S and the outer edge of the first terminal 16 when viewed from the direction α is greater than the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S when viewed from the direction α. ​​The distance D2 between the outer edge S1 of the gap S and the outer edge of the second terminal 17 when viewed from the direction α is greater than the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S when viewed from the direction α. ​​The distance D1 is the shortest distance between the outer edge S1 of the gap S and the outer edge of the first terminal 16 when viewed from the direction α. ​​The distance D2 is the shortest distance between the outer edge S1 of the gap S and the outer edge of the second terminal 17 when viewed from the direction α.

[0039] The dimensions of each part are as follows, as an example: The length of one side of the substrate 21 is 1 to 50 mm. The diameter of the light-transmitting region 1a, the diameter of the outer edge 121E of the first portion 121, and the diameter of the opening 40a are each 0.3 to 45 mm. The diameter of the outer edge S1 of the void S and the diameter of the outer edge 122E of the second portion 122 are each 0.5 to 48 mm. The thickness T of the void S is several tens of nm to several tens of μm. [Functions and Effects]

[0040] In the Fabry-Perot interference filter 1, when viewed from the direction α, the area where the first portion 121 is located and corresponds to the light-transmitting region 1a is larger than the area of ​​the annular area where the second portion 122 that deforms due to electrostatic force is located and surrounds the light-transmitting region 1a. This ensures a sufficient width for the light-transmitting region 1a to transmit light having a desired wavelength. Because light that passes through the first portion 121 becomes signal light, while light that passes through the second portion 122 that deforms due to electrostatic force becomes noise light, this configuration is extremely effective in obtaining signals with an excellent S / N ratio. Furthermore, in the Fabry-Perot interference filter 1, the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S when viewed from the direction α is greater than the thickness T of the gap S in the direction α. ​​This ensures a sufficient width for the second portion 122 that deforms due to electrostatic force, improving the parallelism of the first portion 121 with respect to the fixed mirror unit 11 and suppressing the transmission of noise light. Therefore, the Fabry-Perot interference filter 1 can appropriately secure the light transmission region 1a for transmitting light having a desired wavelength.

[0041] The configuration in which "the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S when viewed from the direction α is greater than the thickness T of the gap S in the direction α" makes it possible to sufficiently move the first portion 121 along the direction α simply by slightly deforming at least a portion of the second portion 122, and also makes it possible to reduce the power required to deform at least a portion of the second portion 122. Therefore, this configuration is extremely effective in a Fabry-Perot interference filter 1 having a configuration in which "the area of ​​the region in which the first portion 121 is located and which corresponds to the light-transmitting region 1a when viewed from the direction α is greater than the area of ​​the annular region in which the second portion 122 is located and which surrounds the light-transmitting region 1a when viewed from the direction α." The Fabry-Perot interference filter 1 having the configuration in which "when viewed from the direction α, the area of ​​the region where the first portion 121 is arranged and which corresponds to the light transmission region 1a is larger than the area of ​​the annular region where the second portion 122 is arranged and which surrounds the light transmission region 1a when viewed from the direction α" can be used not only under atmospheric pressure environments but also under pressures such as 10 ４ Pa to 10 －６ It may also be used in a reduced pressure environment of 100 Pa.

[0042] In the Fabry-Perot interference filter 1, the light-shielding layer 45, in which the openings 45a corresponding to the light-transmitting regions 1a are formed, faces the second portion 122 in the direction α. ​​This makes it possible to prevent light that has passed through the second portion 122, which is deformed by electrostatic force, from being emitted, thereby further improving the S / N ratio of the signal light that has passed through the first portion 121.

[0043] In the Fabry-Perot interference filter 1, a plurality of grooves 35 and a plurality of through holes 36 are formed in the inner portion 122a of the second portion 122. This makes it possible to make the second portion 122 more easily deformable, and further improves the parallelism of the first portion 121 with respect to the fixed mirror portion 11.

[0044] In the Fabry-Perot interference filter 1, the width C of the outer portion 122b when viewed from the direction α is larger than the width B of the inner portion 122a when viewed from the direction α. ​​This makes it easier to deform the second portion 122, and further improves the parallelism of the first portion 121 with respect to the fixed mirror portion 11.

[0045] In the Fabry-Perot interference filter 1, the width C of the outer portion 122b when viewed from the direction α is larger than the thickness T of the gap S in the direction α. ​​This makes it easier for the second portion 122 to deform, and further improves the parallelism of the first portion 121 with respect to the fixed mirror portion 11.

[0046] In the Fabry-Perot interference filter 1, the area of ​​the slit S when viewed from the direction α is larger than half the area of ​​the first laminate 32 when viewed from the direction α, and is also larger than half the area of ​​the second laminate 34 when viewed from the direction α. ​​As a result, the area of ​​the slit S is larger than the area of ​​the Fabry-Perot interference filter 1 when viewed from the direction α, and the area of ​​the light transmission region 1a is larger than the area of ​​the slit S when viewed from the direction α. ​​This makes it possible to ensure a sufficiently large light transmission region 1a for transmitting light having a desired wavelength while preventing the Fabry-Perot interference filter 1 from becoming too large.

[0047] In the Fabry-Perot interference filter 1, the distance D1 between the outer edge S1 of the air gap S and the outer edge of the first terminal 16 when viewed from the direction α is greater than the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the air gap S when viewed from the direction α, and the distance D2 between the outer edge S1 of the air gap S and the outer edge of the second terminal 17 when viewed from the direction α is greater than the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the air gap S when viewed from the direction α. ​​As a result, when an external force acts on each of the first terminal 16 and the second terminal 17, the external force is less likely to reach the movable mirror portion 12, and therefore damage to the movable mirror portion 12 that faces the fixed mirror portion 11 across the air gap S can be suppressed.

[0048] In the Fabry-Perot interference filter 1, when viewed from the direction α, the outer edge 121E of the first portion 121 and the outer edge S1 of the slit S have circular shapes with the same center. This makes it possible to more appropriately ensure a light-transmitting region 1a for transmitting light having a desired wavelength. Furthermore, throughout the entire area of ​​the second portion 122 surrounding the light-transmitting region 1a (i.e., in any cross section including the line L), the distance from the outer edge of the light-transmitting region 1a to the outer edge S1 of the slit S is greater than the thickness T of the slit S. This ensures a sufficient width for the second portion 122 to deform due to electrostatic force throughout the entire area of ​​the second portion 122. This further improves the parallelism of the first portion 121 with respect to the fixed mirror portion 11, thereby further improving the signal-to-noise ratio of the signal light transmitted through the first portion 121. [Modification]

[0049] The present disclosure is not limited to the above-described embodiment. For example, the movable mirror unit 12 may be configured so that the distance between the fixed mirror unit 11 and the first unit 121 in the light transmission region 1a is adjusted by deformation of at least a portion of the second unit 122 due to electrostatic force. As an example, the inner portion 122a of the second unit 122 may have multiple grooves 35 formed therein, but not multiple through holes 36. Alternatively, the inner portion 122a of the second unit 122 may have multiple through holes 36 formed therein, but not multiple grooves 35. If at least one of the multiple grooves 35 and the multiple through holes 36 is formed in the inner portion 122a, the second unit 122 can be more easily deformed, and the parallelism of the first unit 121 relative to the fixed mirror unit 11 can be further improved.

[0050] In the above embodiment, both the distance D1 between the outer edge S1 of the gap S and the outer edge of the first terminal 16 and the distance D2 between the outer edge S1 of the gap S and the outer edge of the second terminal 17 are greater than the distance A between the outer edge 121E of the first portion 121 and the outer edge S1 of the gap S, but the distance D1 or the distance D2 may be greater than the distance A. When the distance D1 is greater than the distance A, an external force acting on the first terminal 16 is less likely to reach the movable mirror unit 12. When the distance D2 is greater than the distance A, an external force acting on the second terminal 17 is less likely to reach the movable mirror unit 12. Therefore, in either case, damage to the movable mirror unit 12, which faces the fixed mirror unit 11 across the gap S, can be suppressed.

[0051] The movable mirror section 12 may be configured by arranging a mirror layer (e.g., a metal film, etc.) in a layer corresponding to the second stack 34 in the first portion 121. In that case, the mirror layer constituting the movable mirror section 12 may not be arranged in the second portion 122. The fixed mirror section 11 may be configured by arranging a mirror layer (e.g., a metal film, etc.) in a portion of the layer corresponding to the first stack 32 that faces the first portion 121 in the direction α. ​​In that case, the mirror layer constituting the fixed mirror section 11 may not be arranged in a portion of the layer corresponding to the first stack 32 that faces the second portion 122 in the direction α. ​​However, the above-mentioned membrane-type Fabry-Perot interference filter 1 (i.e., a Fabry-Perot interference filter 1 configured by depositing multiple films on the substrate 21) has the advantages of relatively simplified manufacturing processes, low manufacturing costs, and high mass productivity.

[0052] In the above embodiment, when viewed from direction α, the entire second portion 122 was located outside the opening 45a of the light-shielding layer 45, but the inner edge portion of the second portion 122 may also be located inside the opening 45a of the light-shielding layer 45.

[0053] 1...Fabry-Perot interference filter, 1a...light transmission region, 11...fixed mirror portion, 12...movable mirror portion, 13...fixed electrode, 15...movable electrode, 16...first terminal, 17...second terminal, 32...first stack (fixed layer), 34...second stack (movable layer), 35...groove, 36...through hole, 45...light-shielding layer, 45a...opening, 121...first portion, 121E...outer edge, 122...second portion, 122a...inner portion, 122b...outer portion, S...gap, S1...outer edge, α...direction.

Claims

1. A Fabry-Perot interference filter comprising: a fixed layer including a fixed mirror portion; and a movable layer including a movable mirror portion facing the fixed mirror portion across a gap, wherein the movable mirror portion includes: a first portion corresponding to a light-transmitting region; and a second portion surrounding the first portion when viewed from the direction in which the fixed mirror portion and the movable mirror portion face each other, wherein the movable mirror portion is configured so that the distance between the fixed mirror portion and the first portion in the light-transmitting region is adjusted by deformation of at least a portion of the second portion due to electrostatic force, wherein the area of ​​the region in which the first portion is located and which corresponds to the light-transmitting region when viewed from the direction is greater than the area of ​​the annular region in which the second portion is located and which surrounds the light-transmitting region when viewed from the direction, and wherein the distance between the outer edge of the first portion and the outer edge of the gap when viewed from the direction is greater than the thickness of the gap in the direction.

2. The Fabry-Perot interference filter according to claim 1, further comprising a light-shielding layer having openings formed therein corresponding to said light-transmitting regions.

3. A Fabry-Perot interference filter as described in claim 1 or 2, wherein the second portion includes an inner portion surrounding the first portion when viewed from the direction, and an outer portion surrounding the inner portion when viewed from the direction, and the inner portion is formed with at least one of a plurality of grooves surrounding the first portion when viewed from the direction, and a plurality of through holes opening on both sides in the direction.

4. The Fabry-Perot interference filter according to claim 3, wherein the width of said outer portion when viewed from said direction is greater than the width of said inner portion when viewed from said direction.

5. A Fabry-Perot interference filter according to claim 3 or 4, wherein the width of said outer portion when viewed in said direction is greater than the thickness of said gap in said direction.

6. A Fabry-Perot interference filter according to any one of claims 1 to 5, wherein the area of ​​the gap when viewed from the said direction is larger than half the area of ​​the fixed layer when viewed from the said direction, and larger than half the area of ​​the movable layer when viewed from the said direction.

7. A Fabry-Perot interference filter according to any one of claims 1 to 6, further comprising a first terminal and a second terminal, wherein the fixed layer further comprises a fixed electrode electrically connected to the first terminal, and the movable layer further comprises a movable electrode electrically connected to the second terminal, and at least one of the distance between the outer edge of the gap and the outer edge of the first terminal when viewed from the direction and the distance between the outer edge of the gap and the outer edge of the second terminal when viewed from the direction is greater than the distance between the outer edge of the first portion and the outer edge of the gap when viewed from the direction.

8. A Fabry-Perot interference filter according to any one of claims 1 to 7, wherein when viewed from the direction, the outer edge of the first portion and the outer edge of the gap have a circular shape with the same center.

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