Light source device

Abstract

To provide a light source device that can quickly change the wavelength of emitted light.SOLUTION: A light source device includes an optical amplifier, a spectroscopic element, a spatial phase modulation element, and a control portion. The optical amplifier amplifies and emits light. The spectroscopic element separates the light from the optical amplifier according to the wavelength. The spatial phase modulation element includes a base portion and a plurality of grating elements that reflect the light separated by the spectroscopic element, and displaces at least some of the grating elements relative to the base portion, applies the phase modulation to the light separated by the spectroscopic element, and emits diffracted light along an incident optical path from the spectroscopic element for some wavelengths in the wavelength range of the light separated by the spectroscopic element. The control portion controls displacement of the plurality of grating elements with respect to the base portion. The diffracted light emitted from the spatial phase modulation element generates light with a partial wavelength in the spectroscopic element, and the partial wavelength light is amplified by the optical amplifier and then emitted toward the spectroscopic element. The partial wavelength light that has been amplified multiple times by the optical amplifier is output.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a light source device capable of changing the wavelength of emitted light. [Background technology]

[0002] 2. Description of the Related Art Light sources such as laser light sources that are capable of changing the wavelength of light they emit are used in the fields of optical communications and inspection devices.

[0003] For example, optical coherence tomography (OCT) is a well-known example of an examination device that can non-invasively acquire information about a tomographic image of a subject. Swept source OCT (SS-OCT), one type of OCT, uses a light source that changes the wavelength of emitted light over a wide band over time, and acquires the intensity of light produced by interference between sample light and reference light for each wavelength. For this reason, SS-OCT uses a wavelength-swept light source (frequency-swept light source) that can sweep the wavelength of output light over a wide band.

[0004] An example of such a wavelength-swept light source is an external resonator-type wavelength-swept light source that combines a gain medium that generates light with a vibrating mirror of a microelectronic mechanical system (MEMS) (see, for example, Patent Document 1). In this external resonator-type wavelength-swept light source, light having a certain range of wavelengths emitted from the gain medium is split according to wavelength using a diffraction grating or the like, and the reciprocating motion of the MEMS vibrating mirror is used to selectively reflect light of a desired wavelength and return it to the gain medium, thereby amplifying the light and sweeping the wavelength of the light emitted from the light source. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-148109 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in an external cavity wavelength swept light source using a MEMS vibrating mirror, for example, the time required to sweep the wavelength of the light emitted from the light source depends on the vibration period of the MEMS vibrating mirror. In other words, the speed at which the wavelength of the light emitted from the light source is changed is determined by the vibration period of the MEMS vibrating mirror.

[0007] Furthermore, in an external resonator type wavelength swept light source using a MEMS vibrating mirror, the wavelength of the light emitted from the light source can only be changed sequentially, for example, in the direction from the maximum wavelength to the minimum wavelength or from the minimum wavelength to the maximum wavelength in a specified wavelength range, by the vibration of the MEMS vibrating mirror.

[0008] Therefore, there is room for improvement in external resonator type wavelength swept light sources, for example, in terms of quickly changing the wavelength of the emitted light.

[0009] The present invention has been made in view of the above-mentioned problems, and has an object to provide a light source device that can quickly change the wavelength of emitted light. [Means for solving the problem]

[0010] To solve the above problems, a light source device according to a first aspect includes an optical amplifier, a spectroscopic element, a spatial phase modulator, and a control unit. The optical amplifier amplifies and emits light. The spectroscopic element disperses the light emitted from the optical amplifier according to wavelength. The spatial phase modulator has a base and a plurality of grating elements that reflect the light dispersed by the spectroscopic element. At least some of the grating elements are displaced relative to the base to perform phase modulation on the light dispersed by the spectroscopic element, and diffracted light of some wavelengths in the wavelength range of the light dispersed by the spectroscopic element is emitted toward the spectroscopic element along an incident light path from the spectroscopic element. The control unit controls the displacement of the plurality of grating elements relative to the base. The diffracted light emitted from the spatial phase modulator generates light of the certain wavelengths in the spectroscopic element, and the light of the certain wavelengths is amplified by the optical amplifier and then emitted toward the spectroscopic element. The light of the certain wavelengths that has been amplified multiple times by the optical amplifier is output. The plurality of grating elements include a plurality of ribbon-shaped portions. Each of the plurality of ribbon-shaped portions has a long, thin ribbon shape extending along a first direction, flexibility, and a reflecting portion having a light-reflecting surface on the opposite side from the base portion. The plurality of ribbon-shaped portions are aligned along a second direction perpendicular to the first direction. The reflecting portion of each of the plurality of ribbon-shaped portions faces the base portion across a space. Each of the plurality of ribbon-shaped portions includes a connecting portion connected to the base portion at each of both ends in the first direction. The base portion includes an electrode facing each of the reflecting portions. The control unit adjusts the potential difference applied between the reflecting portion of each of the plurality of ribbon-shaped portions and the electrode to control the amount of deflection of the plurality of ribbon-shaped portions due to the electrostatic force between the reflecting portion of each of the plurality of ribbon-shaped portions and the electrode, thereby controlling the amount of displacement of the reflecting portion of each of the plurality of ribbon-shaped portions relative to the base portion. The spectroscopic element emits the light emitted from the optical amplifier in the second direction at different angles according to the wavelength, and irradiates the light onto the reflecting portions of the plurality of ribbon-shaped portions. The control unit controls the amount of bending of the plurality of ribbon-shaped portions, thereby causing at least some of the plurality of ribbon-shaped portions to function as blazed diffraction gratings. An angle formed by the light of the certain wavelengths incident on the blazed diffraction grating from the spectroscopic element with respect to the blazed diffraction grating is the same as an angle formed by the diffracted light of the certain wavelengths emitted from the blazed diffraction grating with respect to the blazed diffraction grating.

[0011] A light source device according to a second aspect is the light source device according to the first aspect, wherein the optical amplifier includes a semiconductor optical amplifier, a booster optical amplifier, or a semiconductor laser.

[0012] A light source device according to a third aspect is the light source device according to the first or second aspect, wherein the dispersive element includes a diffraction grating.

[0013] A light source device according to a fourth aspect is a light source device according to any one of the first to third aspects, wherein the control unit switches from a state in which the portion of wavelengths includes a first wavelength to a state in which the portion of wavelengths includes a second wavelength different from the first wavelength by changing the displacement pattern of the plurality of grating elements relative to the base portion from a first pattern to a second pattern using the spatial phase modulation element.

[0014] A light source device according to a fifth aspect is the light source device according to any one of the first to third aspects, wherein the certain wavelengths include a plurality of different wavelengths that are spaced apart from one another.

[0015] A light source device according to a sixth aspect is the light source device according to the fifth aspect, wherein the control unit changes the displacement pattern of the plurality of grating elements relative to the base portion from a first pattern to a second pattern using the spatial phase modulation element, thereby switching from a state in which the plurality of wavelengths include a 1A wavelength and a 1B wavelength to a state in which the plurality of wavelengths include a 2A wavelength different from the 1A wavelength and a 2B wavelength different from the 1B wavelength.

[0016] A light source device according to a seventh aspect is the light source device according to any one of the first to sixth aspects, and includes a first light guiding unit, an optical path changing optical system, and a second light guiding unit. The first light guiding unit guides light emitted from the optical amplifier toward the optical path changing optical system. The optical path changing optical system guides light emitted from the optical amplifier and passing through the first light guiding unit toward the spectroscopic element, and guides light of the certain wavelengths generated by the spectroscopic element in response to the diffracted light emitted from the spatial phase modulator to the second light guiding unit. The second light guiding unit includes a first light output unit that outputs a certain light of the light guided to the second light guiding unit by the optical path changing optical system to the outside of the second light guiding unit, and a light guiding portion that guides the remaining light, excluding the certain light, of the light guided to the second light guiding unit by the optical path changing optical system toward the optical amplifier.

[0017] A light source device according to an eighth aspect is the light source device according to any one of the first to sixth aspects, further comprising a third light guiding unit and a partial reflection optical system. The third light guiding unit guides the light emitted from a first end face of the optical amplifier toward the spectroscopic element and guides the light of the partial wavelengths generated by the spectroscopic element in response to the diffracted light emitted from the spatial phase modulation element toward the first end face of the optical amplifier. The partial reflection optical system transmits and outputs a portion of the light emitted from a second end face of the optical amplifier, and reflects the remaining light, excluding the portion of the light, toward the second end face.

[0019] No. 9 The light source device according to the aspect ofThe optical amplifier includes an optical spectroscopic element, a spatial phase modulator, and a control unit. The optical amplifier amplifies and emits light. The spectroscopic element disperses the light emitted from the optical amplifier according to wavelength. The spatial phase modulator has a base and a plurality of grating elements that reflect the light dispersed by the spectroscopic element, and performs phase modulation on the light dispersed by the spectroscopic element by displacing at least some of the grating elements relative to the base, thereby emitting diffracted light toward the spectroscopic element along an incident optical path from the spectroscopic element for some wavelengths within the wavelength range of the light dispersed by the spectroscopic element. The control unit controls the displacement of the plurality of grating elements relative to the base. The diffracted light emitted from the spatial phase modulator generates light of the certain wavelengths in the spectroscopic element, and the light of the certain wavelengths is amplified by the optical amplifier and then emitted toward the spectroscopic element. The light of the certain wavelengths that has been amplified multiple times by the optical amplifier is output. The spatial phase modulation element includes a plurality of reflecting elements arranged in a matrix. Each of the plurality of reflecting elements includes a movable reflecting portion that faces the base portion across a space and has a light-reflecting surface on the side opposite the base portion, and a flexible supporting portion that supports the movable reflecting portion at multiple locations and is connected to the base portion. The plurality of grating elements include the movable reflecting portion of each of the plurality of reflecting elements. The base portion includes an electrode facing each of the movable reflecting portions. The control portion adjusts the potential difference applied between the movable reflecting portion and the electrode in each of the plurality of reflecting elements, thereby controlling the electrostatic force between the movable reflecting portion and the electrode. R the support portion of deflection Control the amount of , displacement of the movable reflecting portion relative to the base portion amount Control. The plurality of reflecting elements are arranged in a matrix, with M (M is a natural number) reflecting elements arranged in a first direction and N (N is a natural number) reflecting elements arranged in a second direction. The spectroscopic element emits light emitted from the optical amplifier in the second direction at different angles according to wavelength, and irradiates the movable reflecting portion of each of the plurality of reflecting elements. The control unit controls the amount of displacement of the movable reflecting portion of each of the plurality of reflecting elements relative to the base portion, thereby causing at least some of the plurality of reflecting elements to function as a blazed diffraction grating. The angle formed by the light of the certain wavelengths incident on the blazed diffraction grating from the spectroscopic element and the diffracted light of the certain wavelengths emitted from the blazed diffraction grating and the blazed diffraction grating is the same. [Effects of the Invention]

[0020] 1st to 3rd 9 In any of the light source devices according to the above aspects, for example, by changing the pattern of displacement of the plurality of grating elements relative to the base portion, it is possible to quickly change the wavelength of light selectively returned to the spectroscopic element from the light in a predetermined wavelength range dispersed by the spectroscopic element. As a result, for example, the wavelength of the output light output from the light source device after multiple amplifications can be quickly switched. Therefore, for example, the wavelength of the light emitted by the light source device can be quickly changed.

[0021] According to the light source device of the fourth aspect, for example, by changing the pattern of displacement of the grating elements relative to the base from a first pattern to a second pattern, the wavelength of the light output from the light source device can be changed randomly, and as a result, for example, the wavelength of the light emitted by the light source device can be changed quickly.

[0022] In either the fifth or sixth aspect of the light source device, for example, the wavelengths of light selectively returned to the spectroscopic element from the light in a predetermined wavelength range dispersed by the spectroscopic element include a plurality of different wavelengths that are far apart from each other, so that light of a plurality of different wavelengths that are far apart from each other can be output from the light source device simultaneously.

[0023] According to the light source device of the sixth aspect, for example, by changing the pattern of displacement of the grating elements relative to the base from a first pattern to a second pattern, it is possible to randomly change the wavelengths of the light simultaneously output from the light source device, thereby enabling, for example, the wavelengths of the light simultaneously emitted by the light source device to be quickly changed. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram schematically illustrating an example of the configuration of a light source device according to the first embodiment. [Figure 2] FIG. 2 is a plan view schematically showing an example of the configuration of a grating light valve as a spatial phase modulation element. [Figure 3] FIG. 3 is a cross-sectional view showing a schematic example of the configuration of a grating light valve as a spatial phase modulation element. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic example of the configuration of a grating light valve as a spatial phase modulation element. [Figure 5] FIG. 5 is a diagram showing an example of the operation of a grating light valve as a spatial phase modulation element. [Figure 6] FIG. 6 is a diagram showing an example of the operation of a grating light valve as a spatial phase modulation element. [Figure 7] FIG. 7 is a diagram showing an example of the operation of a grating light valve as a spatial phase modulation element. [Figure 8] FIG. 8 is a diagram schematically illustrating an example of the relationship between the optical path of incident light and the optical path of diffracted light as emitted light in a spatial phase modulation element. [Figure 9]FIG. 9 is a diagram schematically illustrating an example of the relationship between the optical path of incident light and the optical path of diffracted light as emitted light in a spatial phase modulation element. [Figure 10] FIG. 10 is a diagram schematically illustrating an example of the relationship between the optical path of incident light and the optical path of diffracted light as emitted light in a spatial phase modulation element. [Figure 11] FIG. 11 is a graph schematically showing an example of switching of the wavelength of the output light output from the light source device. [Figure 12] FIG. 12 is a graph showing an example of the relationship between wavelength and intensity for output light of a plurality of wavelengths output from a light source device. [Figure 13] FIG. 13 is a cross-sectional view schematically showing an example of a 1A pattern relating to the surface shape of a blazed diffraction grating functionally realized in a spatial light modulation element. [Figure 14] FIG. 14 is a cross-sectional view schematically showing an example of a 1B pattern relating to the surface shape of a blazed diffraction grating functionally realized in a spatial light modulation element. [Figure 15] FIG. 15 is a diagram illustrating an example of a method for generating a composite pattern for returning light of multiple wavelengths to a dispersing element using the surface shape of a blazed diffraction grating functionally realized in a spatial phase modulation element. [Figure 16] FIG. 16 is a cross-sectional view showing a schematic example of a composite pattern relating to the surface shape of a blazed diffraction grating that is functionally realized in a grating light valve as a spatial phase modulation element. [Figure 17] FIG. 17 is a graph schematically showing an example of switching between a plurality of wavelengths in the output light output from the light source device. [Figure 18] FIG. 18 is a diagram schematically showing the configuration of a light source device according to one modified example. [Figure 19] FIG. 19 is a plan view showing a schematic example of the configuration of a flat light valve. [Figure 20] FIG. 20 is a cross-sectional view showing a schematic configuration of one reflecting element and a base portion in a flat light valve. [Figure 21]FIG. 21 is a cross-sectional view showing a schematic configuration of one reflecting element and a base portion in a flat light valve. DETAILED DESCRIPTION OF THE INVENTION

[0025] Various embodiments of the present invention will be described below with reference to the accompanying drawings. The components described in these embodiments are merely examples and are not intended to limit the scope of the present invention. In the drawings, parts having similar configurations and functions are designated by the same reference numerals, and redundant description will be omitted in the following description. Furthermore, for ease of understanding, the dimensions and numbers of each part are exaggerated or simplified as necessary. In each figure, a right-handed XYZ Cartesian coordinate system is attached to Figures 2 to 10, 13 to 16, and 19 to 21 to explain the positional relationships of each element. Here, the X and Y axes extend along the diffraction grating surface (also referred to as the grating surface) P0 of the spatial phase modulator 7 (described later), and the Z axis extends along the normal to the grating surface P0. In the following description, the direction of the arrowhead is referred to as the + (plus) direction, and the opposite direction is referred to as the - (minus) direction.

[0026] Unless otherwise specified, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only express that positional relationship exactly, but also express a state in which there is a relative displacement in terms of angle or distance within a range in which tolerance or equivalent functionality is obtained. Expressions indicating an equal state (e.g., "identical," "equal," "homogeneous," etc.) not only express a state in which there is strict quantitative equality, but also express a state in which there is a difference in which tolerance or equivalent functionality is obtained, unless otherwise specified. Expressions indicating shape (e.g., "square shape" or "cylindrical shape," etc.) not only express the shape exactly geometrically, but also express a shape with, for example, concaves and convexes and chamfers, within a range in which equivalent effects are obtained. The expressions "comprise," "include," "have," "includes," "includes," or "have" of one component are not exclusive expressions that exclude the presence of other components. Unless otherwise specified, "above" and "below" may include cases where two elements are in contact as well as cases where two elements are separated. Unless otherwise specified, "moving in a specific direction" may include not only moving parallel to this specific direction, but also moving in a direction that has a component in this specific direction.

[0027] 1. First Embodiment <1-1. Configuration of the light source device> Fig. 1 is a diagram schematically illustrating an example of the configuration of a light source device 100 according to the first embodiment. In Fig. 1, the traveling direction of light is indicated by a thin dashed arrow.

[0028] The light source device 100 has the configuration of an externally resonated light source device that can amplify and output light of a desired wavelength by selectively returning light of a desired wavelength from the light emitted from the optical amplifier to the optical amplifier using a configuration provided outside the optical amplifier.

[0029] The light source device 100 includes an optical amplifier 1, a spectroscopic element 6, a spatial phase modulation element 7, and a first control unit 10. The light source device 100 also includes, for example, a second control unit 20. In the first embodiment, the light source device 100 includes a first light guiding unit 2, an optical path changing optical system 3, and a second light guiding unit 8. In the example of FIG. 1, the light source device 100 includes an optical fiber 4, which is an optical transmission unit having a function of transmitting light, and a collimator lens 5, which is an optical lens, arranged between the optical path changing optical system 3 and the spectroscopic element 6.

[0030] <<Optical Amplifier 1>> The optical amplifier 1 amplifies and emits light. The optical amplifier 1 emits the light, for example, toward a spectroscopic element 6. The optical amplifier 1 may be an optical gain medium (also referred to as an optical gain medium) that amplifies light, such as a semiconductor laser (laser diode: LD), a semiconductor optical amplifier (SOA), or a booster optical amplifier (BOA).

[0031] The optical amplifier 1 generates light in response to, for example, the application of a voltage. The optical amplifier 1 is driven, for example, by controlling the applied voltage under the control of the second control unit 20. The optical amplifier 1 emits, for example, light having an intensity in a predetermined wavelength range. The predetermined wavelength range is set to, for example, a range having a width of approximately 50 nanometers (nm) to 150 nm. The light having an intensity in the predetermined wavelength range may be, for example, visible light or invisible light. Examples of invisible light include near-infrared light, ultraviolet light, and far-infrared light. The light emitted from the optical amplifier 1 may include, for example, light having an intensity at a wavelength other than the predetermined wavelength range. In the example of FIG. 1, light emitted from one end face (also referred to as the first end face) E1 of the optical amplifier 1 passes through the first light guiding unit 2, the optical path changing optical system 3, the optical fiber 4, and the collimator lens 5 in this order, and is irradiated onto the spectroscopic element 6.

[0032] <<First light guide section 2>> The first light guiding unit 2 guides the light emitted from the optical amplifier 1 toward the optical path changing optical system 3. The first light guiding unit 2 has, for example, a collimator lens 21 which is an optical lens, and an optical fiber 22 which is an optical transmission unit. In the example of Fig. 1, the light emitted from the first end face E1 of the optical amplifier 1 passes through the collimator lens 21 and the optical fiber 22 in this order before entering the optical path changing optical system 3.

[0033] <<Optical path changing optical system 3>> The optical path changing optical system 3 guides the light emitted from the optical amplifier 1 and passed through the first light guiding section 2 toward the spectroscopic element 6. The optical path changing optical system 3 also guides the light from the spectroscopic element 6 to the second light guiding section 8. The light from the spectroscopic element 6 is, for example, light generated in the spectroscopic element 6 in response to diffracted light emitted from the spatial phase modulation element 7. The optical path changing optical system 3 is, for example, an optical system configured using an optical circulator or a polarizing beam splitter (PBS).

[0034] 1, the light emitted from the optical amplifier 1 and guided by the optical path changing optical system 3 toward the spectroscopic element 6 passes through the optical fiber 4 and the collimator lens 5 in this order, and is then irradiated onto the spectroscopic element 6. Furthermore, the light generated by the spectroscopic element 6 in response to the diffracted light emitted from the spatial phase modulation element 7 passes through the collimator lens 5 and the optical fiber 4 in this order, and is then incident on the optical path changing optical system 3.

[0035] <<Spectroscopic element 6>> The spectroscopic element 6 disperses the light emitted from the optical amplifier 1 according to wavelength. In the example of FIG. 1 , the spectroscopic element 6 disperses the light emitted from the optical amplifier 1, which passes through the first light guiding unit 2, the optical path changing optical system 3, the optical fiber 4, and the collimator lens 5, in this order, and is then irradiated onto the spectroscopic element 6, according to wavelength. The spectroscopic element 6 emits light having an intensity in a predetermined wavelength range that constitutes the light emitted from the optical amplifier 1, at an angle that corresponds to the wavelength. In other words, the spectroscopic element 6 disperses the light having an intensity in a predetermined wavelength range that constitutes the light emitted from the optical amplifier 1, according to wavelength. A diffraction grating is used for the spectroscopic element 6. In the example of FIG. 1 , a transmissive diffraction grating is used for the spectroscopic element 6, but this is not limiting, and a reflective diffraction grating may also be used for the spectroscopic element 6. Furthermore, the spectroscopic element 6 may be another spectroscopic element, such as a prism.

[0036] The light dispersed by the spectroscopic element 6 is irradiated onto the spatial phase modulation element 7. For this reason, light having an intensity in a predetermined wavelength region is irradiated onto the spatial phase modulation element 7 at an angle according to the wavelength. Here, a reference optical path Ln0 is defined as an optical path that serves as a reference among the optical paths of the light dispersed by the spectroscopic element 6 and irradiated from the spectroscopic element 6 to the spatial phase modulation element 7. As the reference optical path Ln0, for example, the central optical path among the optical paths of the light dispersed by the spectroscopic element 6 and irradiated from the spectroscopic element 6 to the spatial phase modulation element 7 is adopted. For light having an intensity in a predetermined wavelength region, an optical path at a central angle within the range of angles of the light emitted from the spectroscopic element 6 is applied as the central optical path.

[0037] Furthermore, the spectroscopic element 6 generates light corresponding to the diffracted light emitted from the spatial phase modulator 7. This light is emitted toward the optical path changing optical system 3. In the example of Fig. 1, the light generated by the spectroscopic element 6 in response to the diffracted light emitted from the spatial phase modulator 7 passes through the collimator lens 5 and the optical fiber 4 in this order, and enters the optical path changing optical system 3.

[0038] <<Spatial Phase Modulator 7>> The spatial phase modulation element 7 performs phase modulation on the light irradiated from the spectroscopic element 6. This allows the spatial phase modulation element 7 to emit diffracted light toward the spectroscopic element 6, for example. The spatial phase modulation element 7 may be, for example, a grating light valve, which is a type of optical phase array, as shown in FIGS. 2 to 4. FIG. 2 is a plan view schematically showing an example of the configuration of a grating light valve. FIG. 2 also shows a schematic view of a portion of the configuration of a grating light valve. FIGS. 3 and 4 are cross-sectional views each showing an example of the configuration of a grating light valve. FIGS. 5 to 7 are schematic views each showing an example of the operation of a grating light valve. In FIGS. 2 to 7, a first direction along a main surface (also referred to as a first main surface) Sf1 on the +Z direction side of a substrate 71s constituting the grating light valve is the +Y direction, a second direction along the first main surface Sf1 and perpendicular to the +Y direction is the +X direction, and a third direction along a normal to the first main surface Sf1 is the +Z direction.

[0039] The grating light valve has, for example, a base portion 71 and a plurality of ribbon-shaped portions (also referred to as ribbons) 72 as a plurality of grating elements that reflect the light dispersed by the dispersing element 6.

[0040] The base portion 71 has, for example, a substrate 71s and an electrode (also referred to as a reference electrode) 71e. The substrate 71s is, for example, a plate-shaped substrate such as a silicon substrate. The reference electrode 71e is located along a first main surface Sf1 of the substrate 71s. The reference electrode 71e is, for example, a metal film formed on the first main surface Sf1 of the substrate 71s.

[0041] The plurality of ribbons 72 are located on the first main surface Sf1 of the substrate 71s. Each of the plurality of ribbons 72 is formed of, for example, a fine structure made of an amorphous silicon nitride film or the like. The plurality of ribbons 72 are aligned along the X direction. The number of the plurality of ribbons 72 is set to, for example, approximately 2000 to 4000. More specifically, the number of the plurality of ribbons 72 is set to, for example, approximately 3000. Here, the plurality of ribbons 72 are not in contact with each other. In other words, there is a minute gap between two adjacent ribbons 72 among the plurality of ribbons 72.

[0042] Each of the multiple ribbons 72 has a long, thin ribbon-like shape extending along the Y direction. For example, as shown in Fig. 2, when viewed in a plan view, each of the multiple ribbons 72 has a rectangular shape with a short side direction along the X direction and a long side direction along the Y direction. The length (also referred to as width) of each ribbon 72 in the short side direction is set to, for example, about 2 micrometers (µm) to 25.5 µm, and the length of each ribbon 72 in the long side direction is set to, for example, about 1 millimeter (mm) to 3 mm.

[0043] Each of the multiple ribbons 72 has, for example, a reflecting portion 72r and a connecting portion 72c. In each ribbon 72, the reflecting portion 72r is located in the center in the Y direction, and the connecting portions 72c are located at both ends in the Y direction. In other words, in each ribbon 72, the connecting portion (also referred to as a first connecting portion) 72c, the reflecting portion 72r, and the connecting portion (also referred to as a second connecting portion) 72c are located in this order in the Y direction.

[0044] The reflecting portion 72r has a surface (also referred to as a light-reflecting surface) that specularly reflects light on the side opposite to the base portion 71. For example, the light-reflecting surface is a surface parallel to the XY plane. For example, the surface of each ribbon 72 is configured to be covered with a thin metal film such as aluminum that specularly reflects light. As a result, for example, the surface of the reflecting portion 72r of each ribbon 72 opposite to the base portion 71 functions as a light-reflecting surface. Here, for example, since the reflecting portion 72r has a light-reflecting surface, the reflecting portion 72r of each ribbon 72 can reflect light dispersed by the spectroscopic element 6. In other words, for example, the multiple ribbons 72 as multiple grating elements can reflect light dispersed by the spectroscopic element 6. Furthermore, the thin metal film that forms the surface of each ribbon 72 functions as an electrode (also referred to as a movable electrode).

[0045] The connecting portion 72c is a portion connected to the base portion 71. For example, as shown in Fig. 3, each of the plurality of ribbons 72 includes a connecting portion 72c connected to the base portion 71 at both ends in the Y direction. In other words, for example, each of the plurality of ribbons 72 is connected to the first main surface Sf1 of the base portion 71 at both ends in the Y direction.

[0046] Here, the reflecting portion 72r of each of the multiple ribbons 72 faces the base portion 71 across a space Sp1. The reflecting portion 72r of each ribbon 72 faces the reference electrode 71e of the base portion 71 across the space Sp1. In other words, the reference electrode 71e of the base portion 71 faces the reflecting portions 72r of each of the multiple ribbons 72. From another perspective, for example, each of the multiple ribbons 72 is installed on the substrate 71s so as to straddle the reference electrode 71e without making contact with it.

[0047] Each of the multiple ribbons 72 is flexible. Here, for example, when a potential difference is applied between the ribbon 72, which functions as a movable electrode, and the reference electrode 71e, an electrostatic force is generated between the reflective portion 72r and the reference electrode 71e, attracting the reflective portion 72r to the reference electrode 71e. This electrostatic force causes the ribbon 72 to bend. FIG. 3 illustrates the ribbon 72 in an unbent state (also referred to as a reference state), and FIG. 4 illustrates the ribbon 72 in a bent state. As shown in FIGS. 3 and 4, the ribbon 72 is displaced in the Z direction when it bends. Here, for example, the position of the reflective portion 72r in the reference state in which the ribbon 72 is unbent is used as a reference, and the reflective portion 72r is displaced in the −Z direction when the ribbon 72 bends.

[0048] The grating light valve serving as the spatial phase modulation element 7 displaces the ribbons 72 by an amount corresponding to the signal by, for example, bending the ribbons 72 with an electrostatic force corresponding to the signal from the first control unit 10. The grating light valve has, for example, a CMOS (Complementary Metal Oxide Semiconductor) driver (not shown) or the like for individually applying an electric potential to each of the plurality of ribbons 72 according to the signal from the first control unit 10.

[0049] In the first embodiment, for example, the first control unit 10 can adjust the potential difference applied between the reflecting portion 72r and the reference electrode 71e for each of the multiple ribbons 72, thereby bending the ribbons 72 using the electrostatic force between the reflecting portion 72r and the reference electrode 71e, and controlling the displacement of the reflecting portion 72r relative to the base portion 71.

[0050] For example, a first potential serving as a fixed reference, such as 0 volts (V) to −12 V, is applied to the reference electrode 71e, and a second potential equal to or greater than the first potential is applied to each of the ribbons 72. The second potential is set, for example, so that the difference (potential difference) between the second potential and the first potential is a desired potential difference within a predetermined range, such as 0 V to 25 V. For example, the second potential is variable. For example, different second potentials can be applied to the ribbons 72. This allows, for example, the displacement amounts of the reflecting portions 72r to be freely varied among the ribbons 72. After the ribbons 72 are deflected by electrostatic force corresponding to the potential difference applied between the ribbons 72 and the reference electrode 71e, when the potential difference applied between the ribbons 72 and the reference electrode 71e becomes substantially zero, the ribbons 72 return to their undeflected reference state due to their elastic force. At this time, the displacement amount of the reflecting portion 72r returns to zero.

[0051] FIG. 5 illustrates a first state in which the displacements of the multiple reflecting portions 72r in the multiple ribbons 72 are equal and zero. In this case, the light-reflecting surfaces of the multiple reflecting portions 72r are located along the grating plane P0, and the grating light valve serving as the spatial phase modulator 7 functions as a mirror. The reference light path Ln0 is, for example, an optical path along the normal to the light-reflecting surface of the reflecting portion 72r. In this case, the reference light path Ln0 is an optical path along the normal to the grating plane P0 of the grating light valve serving as the spatial phase modulator 7. Here, the grating plane P0 of the grating light valve is a plane along the XY plane. The normal to the grating plane P0 is an imaginary straight line extending along the Z direction.

[0052] Fig. 6 illustrates a second state in which the amount of displacement of the reflecting portion 72r in the X direction changes periodically, and the grating light valve serving as the spatial phase modulator 7 functions as a blazed diffraction grating. Fig. 7 illustrates a third state in which the amount of displacement of the reflecting portion 72r in the X direction changes periodically, and the grating light valve serving as the spatial phase modulator 7 functions as a blazed diffraction grating. For convenience, each of Figs. 6 and 7 includes the grating pitch d (also referred to as the grating pitch), which is the period of displacement in the blazed diffraction grating, and the angle θb (also referred to as the blaze angle), which is the angle formed by the sawtooth-shaped inclined surface with respect to the grating plane P0.

[0053] The grating pitch d and the blaze angle θb are different between the second state shown in Fig. 6 and the third state shown in Fig. 7. The grating light valve as the spatial phase modulation element 7 can function as a blazed diffraction grating in which the grating pitch d and the blaze angle θb are variable, for example, by controlling the amount of bending of the plurality of ribbons 72 by controlling the second potential applied to each of the plurality of ribbons 72.

[0054] In the first embodiment, for example, the spectroscopic element 6 is arranged to emit light at different angles according to wavelength in the X direction, which is the second direction in which the ribbons 72 serving as the grating elements are arranged. The spectroscopic element 6 is arranged so that the dispersed light emitted is irradiated onto the ribbons 72 serving as the grating elements. For example, the light emitted from the spectroscopic element 6 is irradiated onto the center of each of the ribbons 72 serving as the grating elements in the Y direction, which is the first direction. In other words, the light emitted from the spectroscopic element 6 is irradiated onto the reflecting portions 72r constituting the ribbons 72 serving as the grating elements. Here, the light emitted from the spectroscopic element 6 is irradiated onto a linear or band-shaped region that is approximately centered along the Y direction, which is the first direction, of the ribbons 72 serving as the grating elements. In this case, light of different wavelengths is irradiated onto the light-reflecting surfaces of the reflecting portions 72r in the X direction. For example, it is conceivable that the wavelength of the light emitted from the spectroscopic element 6 and irradiated onto the light-reflecting surfaces of the reflecting portions 72r becomes shorter as it moves in the +X direction.

[0055] Here, for example, a grating light valve serving as the spatial phase modulation element 7 can displace at least some of the ribbons 72 serving as the grating elements relative to the base portion 71. Then, for example, the grating light valve serving as the spatial phase modulation element 7 can perform phase modulation on the light dispersed by the spectroscopic element 6, and emit diffracted light for some wavelengths within a predetermined wavelength range of the light dispersed by the spectroscopic element 6 along the optical path (also referred to as the incident optical path) Li of the incident light from the spectroscopic element 6 toward the spectroscopic element 6. In this way, the grating light valve serving as the spatial phase modulation element 7 can selectively return light of some wavelengths (also referred to as selected wavelengths) of the light dispersed by the spectroscopic element 6 to the spectroscopic element 6.

[0056] 8 to 10 are diagrams each showing a schematic example of the relationship between the optical path of incident light (incident optical path) Li and the optical path of diffracted light as emitted light (also called the emitted optical path) Le in a grating light valve.

[0057] When the grating light valve as the spatial phase modulator 7 functions as a blazed diffraction grating, it can emit diffracted light at an angle corresponding to the grating pitch d in response to the irradiation of incident light. When the grating light valve as the spatial phase modulator 7 functions as a blazed diffraction grating, it is configured in a so-called Littrow configuration, so that for light of a desired wavelength, the angle θi (also called the incident angle) between the normal L0 of the grating surface P0 and the optical path (incident optical path) Li of the incident light is the same as the angle θe (also called the diffraction angle) between the normal L0 of the grating surface P0 and the optical path (exit optical path) Le of the diffracted light. In the Littrow configuration, for example, the diffraction efficiency can be increased as the depth (= d × tan θb) of the sawtooth pattern of the blazed diffraction grating approaches half the desired wavelength. In this case, for example, the incident angle θi, the diffraction angle θe, and the blaze angle θb are the same.

[0058] Here, for example, the positive and negative of the blaze angle θb can be defined such that when the sawtooth-shaped inclined surface slopes toward the −Z direction as it moves toward the +X direction, the blaze angle θb is a negative angle, and when the sawtooth-shaped inclined surface slopes toward the −Z direction as it moves toward the −X direction, the blaze angle θb is a positive angle. In this case, the positive and negative of the incident angle θi and the diffraction angle θe can be defined such that when the incident light path Li and the output light path Le are tilted counterclockwise to form an acute angle with respect to the normal line L0 in a planar view in the +Y direction, the incident angle θi and the diffraction angle θe are negative angles, and when the incident light path Li and the output light path Le are tilted clockwise to form an acute angle with respect to the normal line L0, the incident angle θi and the diffraction angle θe are positive angles.

[0059] For example, the grating light valve serving as the spatial phase modulation element 7 can be set in a Littrow configuration for some wavelengths (selected wavelengths) within a predetermined wavelength range of light dispersed by the spectroscopic element 6 by displacing at least some of the reflecting portions 72r relative to the base portion 71 under the control of the first control unit 10. In this case, the grating light valve serving as the spatial phase modulation element 7 can emit diffracted light of the selected wavelength along the incident optical path Li of the incident light from the spectroscopic element 6 toward the spectroscopic element 6. In other words, for light of the selected wavelength, the angle (incident angle) θi between the normal L0 of the grating surface P0 and the optical path (incident optical path) Li of the incident light is the same as the angle (diffraction angle) θe between the normal L0 of the grating surface P0 and the optical path (exit optical path) Le of the diffracted light. This allows the grating light valve serving as the spatial phase modulation element 7 to selectively return light of some wavelengths (selected wavelengths) of the light dispersed by the spectroscopic element 6 to the spectroscopic element 6. The diffracted light of the selected wavelength emitted from the spatial phase modulation element 7 causes the spectroscopic element 6 to generate light of a part of the wavelength (selected wavelength) within a predetermined wavelength range of the light dispersed by the spectroscopic element 6.

[0060] Here, for example, the grating light valve serving as the spatial phase modulation element 7 can be set in a Littrow configuration for a first wavelength λ1, which is a portion of a wavelength (selected wavelength) within a predetermined wavelength range of light dispersed by the spectroscopic element 6, by displacing at least some of the reflecting portions 72r among the plurality of reflecting portions 72r relative to the base portion 71 under the control of the first control unit 10. Here, as shown in FIG. 9 , for example, in the grating light valve serving as the spatial phase modulation element 7, a blaze angle (also referred to as a first blaze angle) θb1 is set corresponding to the angle (also referred to as a first incident angle) θi1 formed between the optical path (also referred to as a first incident optical path) Li1 of the first wavelength λ1 irradiated from the spectroscopic element 6 toward the spatial phase modulation element 7 and the normal line L0 of the grating surface P0. In this case, the grating light valve serving as the spatial phase modulation element 7 emits diffracted light of the first wavelength λ1 toward the spectroscopic element 6 along the incident optical path (first incident optical path) Li1 of the incident light of the first wavelength λ1 from the spectroscopic element 6. In other words, for light of the selected wavelength, the angle (first incident angle) θi1 formed between the normal L0 to the grating surface P0 and the optical path (first incident optical path) Li1 of the incident light of the first wavelength λ1 is the same as the angle (first diffraction angle) θe1 formed between the normal L0 to the grating surface P0 and the optical path (first exit optical path) Le1 of the diffracted light of the first wavelength λ1. This allows the grating light valve serving as the spatial phase modulation element 7 to selectively return light of the first wavelength λ1, which is light of a partial wavelength (selected wavelength) of the light dispersed by the spectroscopic element 6, to the spectroscopic element 6. The diffracted light of the first wavelength λ1 emitted from the spatial phase modulation element 7 then generates light of the first wavelength λ1, which is a partial wavelength (selected wavelength) of a predetermined wavelength range of the light dispersed by the spectroscopic element 6, in the spectroscopic element 6.

[0061] Furthermore, for example, a grating light valve serving as the spatial phase modulation element 7 can be set in a Littrow configuration for a second wavelength λ2, which is a portion of a wavelength (selected wavelength) within a predetermined wavelength range of light dispersed by the spectroscopic element 6, by displacing at least some of the reflecting portions 72r relative to the base portion 71 under the control of the first control unit 10. The second wavelength λ2 is different from the first wavelength λ1. Here, for example, as shown in FIG. 10 , in the grating light valve serving as the spatial phase modulation element 7, a blaze angle (also referred to as a second blaze angle) θb2 is set corresponding to an angle (also referred to as a second incident angle) θi2 formed between an optical path (also referred to as a second incident optical path) Li2 of the second wavelength λ2 irradiated from the spectroscopic element 6 toward the spatial phase modulation element 7 and a normal line L0 to the grating surface P0. In this case, the grating light valve serving as the spatial phase modulation element 7 emits diffracted light of the second wavelength λ2 toward the spectroscopic element 6 along the incident light path (second incident light path) Li2 of the incident light of the second wavelength λ2 from the spectroscopic element 6. In other words, for the light of the selected wavelength, the angle (second incident angle) θi2 formed between the normal L0 to the grating surface P0 and the light path (second incident light path) Li2 of the incident light of the second wavelength λ2 is the same as the angle (second diffraction angle) θe2 formed between the normal L0 to the grating surface P0 and the light path (second exit light path) Le2 of the diffracted light of the second wavelength λ2. This allows the grating light valve serving as the spatial phase modulation element 7 to selectively return the light of the second wavelength λ2, which is light of a portion of the wavelength (selected wavelength) of the light dispersed by the spectroscopic element 6, to the spectroscopic element 6. The diffracted light of the second wavelength λ2 emitted from the spatial phase modulation element 7 generates light of the second wavelength λ2 in the spectroscopic element 6 as a partial wavelength (selected wavelength) of the predetermined wavelength range of the light dispersed by the spectroscopic element 6.

[0062] <<Second light guide section 8>> 1, the second light guiding section 8 includes an optical fiber 81 as a light transmitting section, a collimator lens 82 which is an optical lens, and an optical fiber 83 as a light transmitting section. For example, light guided to the second light guiding section 8 by the optical path changing optical system 3 passes through the optical fiber 81, the collimator lens 82, and the optical fiber 83 in this order, and enters the first light output section 84.

[0063] The first light output unit 84 outputs a portion of the light guided to the second light guide unit 8 by the optical path changing optical system 3 as output light to the outside of the second light guide unit 8. For example, an optical fiber coupler (also referred to as a coupler) is used for the first light output unit 84. For example, the coupler outputs a portion of the light incident on the coupler to the outside of the second light guide unit 8 via an optical fiber 85, which is an optical transmission unit, and guides the remaining light of the light incident on the coupler to a light guide portion 86. Here, for example, with respect to the light incident on the coupler, the amount of the remaining light output to the light guide portion 86 is set to be several times to several tens of times greater than the amount of output light output to the outside of the second light guide unit 8 via the optical fiber 85. From another perspective, for example, with respect to the light incident on the coupler, the ratio of the amount of output light output to the outside of the second light guide unit 8 via the optical fiber 85 to the amount of the remaining light output to the light guide portion 86 is set to be, for example, 5 to 20:95 to 80. For example, the ratio between the amount of output light and the amount of remaining light is set to 10:90.

[0064] The light guiding section 86 guides the remaining light, of the light guided by the optical path changing optical system 3 to the second light guiding section 8, excluding a portion of the light (output light) outputted to the outside of the second light guiding section 8 by the first light output section 84, toward the optical amplifier 1. As a result, for example, light incident on the optical amplifier 1 is amplified by the optical amplifier 1 and then emitted toward the spectroscopic element 6. In other words, for example, light of a portion of wavelengths (selected wavelengths) within a predetermined wavelength range, which is generated in the spectroscopic element 6 in response to diffracted light emitted from the spatial phase modulation element 7, is amplified by the optical amplifier 1 and then emitted toward the spectroscopic element 6.

[0065] 1, light guiding section 86 includes an optical fiber 861 as a light transmitting section and a collimator lens 862 as an optical lens. In this case, for example, light guided from first light output section 84 to light guiding section 86 passes through optical fiber 861 and collimator lens 862 in this order, and enters another end face (also referred to as a second end face) E2 of optical amplifier 1 that is different from first end face E1. As a result, for example, light that has entered second end face E2 of optical amplifier 1 is amplified by optical amplifier 1 and then emitted toward spectroscopic element 6.

[0066] In the light source device 100, light emitted from the optical amplifier 1 can pass multiple times through a path (also referred to as an amplification path) that passes through the spectroscopic element 6, the spatial phase modulation element 7, the spectroscopic element 6, and the optical amplifier 1 in this order. As a result, for example, in response to the emission from the optical amplifier 1 of light having an intensity in a predetermined wavelength range, light of a portion of wavelengths (selected wavelengths) that has been amplified multiple times by the optical amplifier 1 can be output. As a result, for example, light having high intensity in a narrow wavelength range can be output from the light source device 100.

[0067] <<First control unit 10>> The first control unit 10 controls the operation of the spatial phase modulation element 7. Specifically, the first control unit 10 controls the displacement of a plurality of ribbons 72 (specifically, a plurality of reflecting portions 72r) as a plurality of grating elements relative to a base portion 71 of the spatial phase modulation element 7. Here, for example, by using a grating light valve as the spatial phase modulation element 7 to change the pattern of displacement of the plurality of ribbons 72 (specifically, a plurality of reflecting portions 72r) as a plurality of grating elements relative to the base portion 71, it is possible to quickly change the light of a portion of wavelengths (selected wavelengths) selectively returned to the spectroscopic element 6 from the light in a predetermined wavelength range dispersed by the spectroscopic element 6. As a result, for example, the wavelength of the output light output from the light source device 100 after multiple amplifications can be quickly switched. Therefore, for example, the wavelength of the light emitted by the light source device 100 can be quickly changed.

[0068] Furthermore, for example, each of the ribbons 72 (specifically, the reflecting portions 72r) as the grating elements is minute, and the amount of displacement of the ribbons 72 (specifically, the reflecting portions 72r) as the grating elements can be controlled with precision. This allows, for example, the wavelength of the light emitted by the light source device 100 to be changed with precision.

[0069] The first control unit 10 is configured to include, for example, a processor such as a CPU (Central Processing Unit), a memory and a storage unit, or an FPGA (Field Programmable Gate Array). The storage unit may be, for example, a non-volatile storage medium that stores a program executable by the CPU or the like. The first control unit 10 controls the operation of the spatial phase modulation element 7 in response to, for example, a signal or information from a control device 200 external to the light source device 100. The signal or information input from the control device 200 to the first control unit 10 includes, for example, a signal or information indicating a displacement pattern of a plurality of ribbons 72 (specifically, a plurality of reflecting portions 72r) serving as a plurality of grating elements relative to a base portion 71 in the spatial phase modulation element 7.

[0070] The control device 200 may be, for example, a personal computer having a CPU, a storage unit, or other suitable computer. The control device 200 generates information indicating a displacement pattern of the ribbons 72 (specifically, the reflecting portions 72r) serving as the grating elements of the spatial phase modulator 7 relative to the base portion 71, in accordance with the surface shape of the blazed diffraction grating corresponding to the light of the desired wavelength (selected wavelength) to be output from the light source device 100. The surface shape of the blazed diffraction grating corresponding to the light of the desired wavelength to be output from the light source device 100 can be determined, for example, by calculation or simulation based on the relative position and orientation relationship between the spectroscopic element 6 and the spatial phase modulator 7, information on the spectroscopic characteristics of the spectroscopic element 6, or by experiments using the light source device 100. Factors that define the surface shape of the blazed diffraction grating include, for example, the blaze angle θb and the grating pitch d.

[0071] The first control unit 10 can, for example, change the displacement pattern of multiple ribbons 72 (specifically, multiple reflecting portions 72r) as multiple grating elements relative to the base portion 71 from a first pattern to a second pattern using a grating light valve as the spatial phase modulation element 7.

[0072] Here, for example, when the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 is set to a first pattern, the grating light valve as the spatial phase modulation element 7 functions as a blazed diffraction grating having a blaze angle (first blaze angle) θb1 corresponding to the angle (first incident angle) θi1 formed between the optical path (first incident optical path) Li1 of the incident light of the first wavelength λ1 irradiated from the dispersive element 6 toward the spatial phase modulation element 7 and the normal L0 of the grating surface P0. Furthermore, for example, when the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 is set to a second pattern, the grating light valve as the spatial phase modulation element 7 functions as a blazed diffraction grating having a blaze angle (second blaze angle) θb2 corresponding to the angle (second incident angle) θi2 formed between the optical path (second incident optical path) Li2 of the incident light of the second wavelength λ2 irradiated from the dispersive element 6 toward the spatial phase modulation element 7 and the normal L0 of the grating surface P0.

[0073] In this case, for example, when the first control unit 10 changes the pattern of displacement of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) serving as the plurality of grating elements relative to the base portion 71 from the first pattern to the second pattern, a state in which some wavelengths (selected wavelengths) within the predetermined wavelength range of light dispersed by the dispersing element 6 include the first wavelength λ1 is switched to a state in which some wavelengths (selected wavelengths) within the predetermined wavelength range of light dispersed by the dispersing element 6 include the second wavelength λ2. Therefore, for example, the wavelength of the output light output from the light source device 100 can be changed randomly. As a result, for example, the wavelength of the light emitted by the light source device 100 can be changed quickly.

[0074] Furthermore, the first control unit 10 may change the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 from the first pattern to a third pattern, for example, by a grating light valve as the spatial phase modulation element 7. Here, for example, when the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 is set to the third pattern, the grating light valve as the spatial phase modulation element 7 emits diffracted light of light having a third wavelength λ3 within the predetermined wavelength range dispersed by the dispersing element 6 toward the dispersing element 6 along the incident optical path Li of the incident light from the dispersing element 6. In this case, for example, when the first control unit 10 changes the pattern of displacement of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 from the first pattern to the third pattern, the state switches from one in which some wavelengths (selected wavelengths) within the predetermined wavelength range of the light dispersed by the dispersive element 6 include the first wavelength λ1 to one in which some wavelengths (selected wavelengths) within the predetermined wavelength range of the light dispersed by the dispersive element 6 include the third wavelength λ3.

[0075] Fig. 11 is a graph showing a schematic example of switching of the wavelength (selected wavelength) of the output light output from light source device 100. In Fig. 11, an example of the spectrum of the output light when the wavelength of the output light output from light source device 100 is a first wavelength λ1 is shown by a curve drawn with a solid line, and an example of the spectrum of the output light when the wavelength of the output light output from light source device 100 is a second wavelength λ2 is shown by a curve drawn with a dashed dotted line. In Fig. 11, an example of the spectrum of the output light when the wavelength of the output light output from light source device 100 is a third wavelength λ3 is shown by a curve drawn with a dashed two-dotted line.

[0076] 11, for example, a possible mode is one in which the wavelength of output light output from light source device 100 is quickly switched from a first wavelength λ1 to a second wavelength λ2 that is farther away from and smaller than the first wavelength λ1. Also, for example, a possible mode is one in which the wavelength of output light output from light source device 100 is quickly switched from the first wavelength λ1 to a third wavelength λ3 that is farther away from and larger than the first wavelength λ1. In this case, the second wavelength λ2 and the third wavelength λ3 may be interchanged.

[0077] In this way, in the light source device 100, for example, as described above, by using a grating light valve as the spatial phase modulation element 7, light of some wavelengths (selected wavelengths) of the light dispersed by the dispersing element 6 is selectively returned to the dispersing element 6, thereby randomly increasing and decreasing the wavelength of the output light output from the light source device 100.

[0078] Incidentally, for example, in an external resonator-type wavelength-swept light source using a MEMS vibrating mirror described in the background art, the wavelength of the output light is swept by oscillating a vibrating mirror that is larger than the ribbon 72 (specifically, the reflecting portion 72r) serving as a lattice element in the light source device 100. For this reason, there is a rate-limiting factor, for example, in that the vibrating mirror can only be oscillated within a certain angle range. Therefore, it is not easy to sweep the wavelength of the output light within a narrow wavelength range, for example, less than 10 nm. In contrast, in the light source device 100 according to the first embodiment, the wavelength of the output light can be swept within a narrow wavelength range, for example, from 1 nm to less than 10 nm, by controlling the amount of displacement of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) serving as a lattice element that is smaller than the MEMS vibrating mirror.

[0079] <<Second control unit 20>> The second control unit 20 is configured to include, for example, a processor such as a CPU (Central Processing Unit), a memory and a storage unit, or an FPGA (Field Programmable Gate Array). The storage unit may be, for example, a non-volatile storage medium that stores a program executable by the CPU or the like. The second control unit 20 may control the optical amplifier 1 in response to a signal from the control device 200, for example.

[0080] <1-2. Summary of the First Embodiment> As described above, in the light source device 100 according to the first embodiment, for example, a grating light valve as the spatial phase modulation element 7 can be used to change the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71. This makes it possible to quickly change, for example, light of a portion of wavelengths (selected wavelengths) that is selectively returned to the spectroscopic element 6 from light in a predetermined wavelength range dispersed by the spectroscopic element 6. As a result, for example, the wavelength of the output light output from the light source device 100 after multiple amplifications can be quickly switched. Therefore, for example, the wavelength of the light emitted by the light source device 100 can be quickly changed.

[0081] Furthermore, in the light source device 100 according to the first embodiment, for example, when the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) serving as the plurality of grating elements relative to the base portion 71 is changed from a first pattern to a second pattern, a state in which some wavelengths (selected wavelengths) within a predetermined wavelength range of light dispersed by the spectroscopic element 6 include a first wavelength λ1 is switched to a state in which some wavelengths (selected wavelengths) within the predetermined wavelength range of light dispersed by the spectroscopic element 6 include a second wavelength λ2. This allows, for example, the wavelength of the output light output from the light source device 100 to be changed randomly. As a result, for example, the wavelength of the light emitted by the light source device 100 can be changed quickly.

[0082] <2. Modifications> The present invention is not limited to the first embodiment described above, and various modifications and improvements can be made without departing from the gist of the present invention.

[0083] <<First Modification>> In the first embodiment, for example, some wavelengths (selected wavelengths) of light selectively returned to the spectroscopic element 6 by the grating light valve serving as the spatial phase modulation element 7 within a predetermined wavelength range of light dispersed by the spectroscopic element 6 may include a plurality of wavelengths that are different from one another. Here, for example, the first control unit 10 may cause the grating light valve serving as the spatial phase modulation element to set a first pattern for the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) serving as the plurality of grating elements relative to the base portion 71, thereby selectively returning light of a plurality of wavelengths that are different from one another within the predetermined wavelength range of light dispersed by the spectroscopic element 6 to the spectroscopic element 6 as light of the selected wavelengths. In this case, for example, the wavelengths of light selectively returned to the spectroscopic element 6 from the light of a predetermined wavelength range dispersed by the spectroscopic element 6 include a plurality of wavelengths that are different from one another, so that light of a plurality of wavelengths that are different from one another can be simultaneously output from the light source device 100.

[0084] Fig. 12 is a graph schematically showing an example of the relationship between wavelength and intensity for output light of multiple wavelengths output from light source device 100. As shown in Fig. 12, a possible embodiment is one in which the multiple wavelengths that are separate from each other include a first A wavelength λ1a and a first B wavelength λ1b that are separate from each other and have a different relationship. Here, for example, the spectrum of the entire output light has a peak at the first A wavelength λ1a (also referred to as the first A peak) and a peak at the first B wavelength λ1b (also referred to as the first B peak).

[0085] Fig. 13 is a cross-sectional view showing an example of a 1A pattern relating to the surface shape of a blazed diffraction grating functionally realized in a grating light valve as the spatial phase modulation element 7. Fig. 14 is a cross-sectional view showing an example of a 1B pattern relating to the surface shape of a blazed diffraction grating functionally realized in a grating light valve as the spatial phase modulation element 7.

[0086] Here, for example, if the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements in the grating light valve serving as the spatial phase modulation element 7 relative to the base portion 71 corresponds to the surface shape of the 1A pattern as shown in Fig. 13, then the blazed diffraction grating functionally realized in the grating light valve serving as the spatial phase modulation element 7 is deemed to have a Littrow arrangement for the 1A wavelength λ1a, which is a portion of the wavelengths (selected wavelengths) within the predetermined wavelength range of light dispersed by the dispersing element 6. Also, here, for example, if the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements in the grating light valve serving as the spatial phase modulation element 7 relative to the base portion 71 corresponds to the surface shape of the 1B pattern as shown in Fig. 14, then the blazed diffraction grating functionally realized in the grating light valve serving as the spatial phase modulation element 7 is deemed to have a Littrow arrangement for the 1B wavelength λ1b, which is a portion of the wavelengths (selected wavelengths) within the predetermined wavelength range of light dispersed by the dispersing element 6.

[0087] In this case, the control device 200 may generate a surface shape pattern (also referred to as a composite pattern) based on the surface shapes of the 1A pattern and the 1B pattern, and generate information indicating a displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) serving as the plurality of grating elements in the spatial phase modulation element 7 relative to the base portion 71, in accordance with the surface shape of the composite pattern of the blazed diffraction grating. Here, for example, a mode is considered in which the control device 200 generates the composite pattern by combining the surface shapes of the 1A pattern and the 1B pattern using a so-called inverse Fourier transform method.

[0088] Fig. 15 is a diagram illustrating an example of a method for generating a composite pattern for returning light of multiple wavelengths to a dispersing element for the surface shape of a blazed diffraction grating functionally realized in a grating light valve as the spatial phase modulation element 7. Fig. 16 is a cross-sectional view schematically showing an example of a composite pattern for the surface shape of a blazed diffraction grating functionally realized in a grating light valve as the spatial phase modulation element 7.

[0089] Here, for example, as shown in Figures 15 and 16, an embodiment may be adopted in which the control device 200 generates a composite pattern so that the composite pattern has a surface shape of a 1A pattern at a location corresponding to an area A1a (also called the 1A area) where light of the 1A wavelength λ1a is irradiated in a grating light valve as the spatial phase modulation element 7, and has a surface shape of a 1B pattern at a location corresponding to an area A1b (also called the 1B area) where light of the 1B wavelength λ1b is irradiated in a grating light valve as the spatial phase modulation element 7.

[0090] Here, for example, by arbitrarily setting the first A wavelength λ1a and the first B wavelength λ1b, it is possible to simultaneously output light of a plurality of different wavelengths that are spaced apart from one another from the light source device 100. As a result, for example, light having high intensity in each of a plurality of different narrow wavelength ranges can be output from the light source device 100.

[0091] 17 is a graph showing an example of switching among multiple wavelengths in output light output from light source device 100. In Fig. 17, an example of the spectrum of output light when the wavelengths of the output light output from light source device 100 are a first A wavelength λ1a and a first B wavelength λ1b as multiple wavelengths is shown by a curve drawn with thin two-dot chain lines, and an example of the spectrum of output light when the wavelengths of the output light output from light source device 100 are a second A wavelength λ2a and a second B wavelength λ2b as multiple wavelengths that are spaced apart from each other is shown by a curve drawn with solid lines. When the wavelengths of the output light output from light source device 100 are the second A wavelength λ2a and the second B wavelength λ2b as multiple wavelengths that are spaced apart from each other, the entire spectrum of the output light has, for example, a peak at the second A wavelength λ2a (also referred to as the second A peak) and a peak at the second B wavelength λ2b (also referred to as the second B peak).

[0092] Here, the first control unit 10 may change the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements relative to the base portion 71 by, for example, a grating light valve as the spatial phase modulation element 7 from a first pattern to a second pattern, thereby switching from a state in which the plurality of wavelengths as a portion of the predetermined wavelength range of the light dispersed by the spectroscopic element 6 include the firstA wavelength λ1a and the firstB wavelength λ1b to a state in which the plurality of wavelengths as a portion of the predetermined wavelength range of the light dispersed by the spectroscopic element 6 include the secondA wavelength λ2a and the secondB wavelength λ2b. In this case, for example, by changing the displacement pattern of the plurality of ribbons 72 (specifically, the plurality of reflecting portions 72r) as the plurality of grating elements of the grating light valve as the spatial phase modulation element 7 relative to the base portion 71 from the first pattern to the second pattern, the plurality of wavelengths of the light simultaneously output from the light source device 100 can be changed randomly. As a result, for example, the plurality of wavelengths of the light simultaneously emitted by the light source device 100 can be changed quickly.

[0093] 17, for example, a possible mode is one in which the two wavelengths of the output light output from light source device 100 can be quickly switched from the first A wavelength λ1a and the first B wavelength λ1b to a second A wavelength λ2a that is spaced apart from the first A wavelength λ1a in the wavelength increasing direction and a second B wavelength λ2b that is spaced apart from the first B wavelength λ1b in the wavelength increasing direction. Here, for example, the second A wavelength λ2a may be shorter than the first A wavelength λ1a, and the second B wavelength λ2b may be shorter than the first B wavelength λ1b.

[0094] Here, the light source device 100, which can rapidly convert multiple wavelengths of light emitted simultaneously, can be applied to, for example, a device or system that performs long-distance, high-precision distance measurement by a dual beat method using beat signals of two wavelengths in a frequency modulation continuous wave (FMCW) distance measurement technology. In long-distance, high-precision distance measurement by the dual beat method, for example, two different wavelengths of light are used simultaneously, and a beat signal equal to the frequency difference between the reference light and the return light from the object is detected by the interference between the reference light and the return light while sweeping each reference light, and the frequency spectrum related to the beat signal is obtained by a fast Fourier transform (FFT) or the like, thereby measuring the distance to the object.

[0095] <<Second Modification>> In the first embodiment and the modified examples, for example, a configuration may be adopted in which light is emitted from the first end face E1 of the optical amplifier 1, and light generated by the spectroscopic element 6 in response to the diffracted light emitted from the spatial phase modulation element 7 is returned to the first end face E1 of the optical amplifier 1.

[0096] Fig. 18 is a diagram schematically showing the configuration of a light source device 100A according to one modified example. In Fig. 18, similar to Fig. 1, the direction of travel of light is indicated by a thin dashed arrow.

[0097] The light source device 100A is based on the light source device 100 according to the first embodiment, and includes a third light guiding section 2A and a partial reflection optical system 9A instead of the first light guiding section 2, the optical path changing optical system 3, the second light guiding section 8, the optical fiber 4, and the collimator lens 5. In other words, the light source device 100A includes the third light guiding section 2A and the partial reflection optical system 9A in addition to the optical amplifier 1, the spectroscopic element 6, the spatial phase modulation element 7, and the first control section 10. The light source device 100 also includes, for example, a second control section 20.

[0098] The third light guiding unit 2A guides the light emitted from the first end face E1 of the optical amplifier 1 toward the spectroscopic element 6, and also guides light of a certain wavelength (selected wavelength) generated in the spectroscopic element 6 in accordance with the diffracted light emitted from the spatial phase modulation element 7 toward the first end face E1 of the optical amplifier 1. For example, a collimator lens 21A, which is an optical lens arranged between the optical amplifier 1 and the spectroscopic element 6, is used for the third light guiding unit 2A.

[0099] The partial reflection optical system 9A transmits a portion of the light emitted from the second end face E2 of the optical amplifier 1 to output it as output light, and reflects the remaining light, excluding this portion of the light emitted from the second end face E2 of the optical amplifier 1, toward the second end face E2 of the optical amplifier 1. The partial reflection optical system 9A includes, for example, a partial reflection mirror 91A and a collimator lens 92A, which is an optical lens. The partial reflection mirror 91A may be, for example, a half mirror or a one-way mirror. The partial reflection mirror 91A transmits a portion of the light emitted from the second end face E2 of the optical amplifier 1 to output it as output light outside the partial reflection optical system 9A via the collimator lens 92A.

[0100] Here, the amount of light emitted from the second end face E2 of the optical amplifier 1 and reflected by the partial reflection mirror 91A toward the second end face E2 of the optical amplifier 1 (the remaining light) is set to be several times to several tens of times greater than the amount of light (a portion of the light) that passes through the partial reflection mirror 91A out of the light emitted from the second end face E2 of the optical amplifier 1. From another perspective, the ratio of the amount of the portion of the light that is irradiated onto the partial reflection mirror 91A from the second end face E2 of the optical amplifier 1 and that passes through the partial reflection mirror 91A (also referred to as transmitted light) to the amount of the remaining light (also referred to as reflected light) reflected by the partial reflection mirror 91A is set to, for example, 5 to 20:95 to 80. For example, the ratio of the amount of transmitted light to the amount of reflected light at the partial reflection mirror 91A is set to, for example, 10:90.

[0101] In the light source device 100A having the above configuration, light emitted from the optical amplifier 1 can travel a plurality of times along a path (also referred to as a round-trip path) that passes through the third light guiding section 2A, the spectroscopic element 6, the spatial phase modulation element 7, the spectroscopic element 6, the third light guiding section 2A, the optical amplifier 1, the partial reflection optical system 9A, and the optical amplifier 1 in this order. In other words, the light emitted from the optical amplifier 1 travels back and forth between the partial reflection optical system 9A and the spatial phase modulation element 7 and is amplified a plurality of times by the optical amplifier 1. As a result, for example, in response to the emission from the optical amplifier 1 of light having intensity in a predetermined wavelength range, light of a portion of wavelengths (selected wavelengths) that has been amplified a plurality of times by the optical amplifier 1 is output. As a result, for example, light having high intensity in a narrow wavelength range can be output from the light source device 100A.

[0102] <<Third Modification>> In the first embodiment and each of the modifications, for example, a flat light valve may be applied to the spatial phase modulation element 7 instead of the grating light valve.

[0103] FIG. 19 is a plan view schematically illustrating an example of the configuration of a planar light valve. FIG. 19 shows a portion of the configuration of a planar light valve. FIGS. 20 and 21 are cross-sectional views each schematically illustrating the configuration of one reflecting element 74 and base portion 73 in a planar light valve. In FIGS. 19 to 21, the first direction along the main surface (also referred to as the second main surface) Sf2 on the +Z direction side of a substrate 73s constituting the planar light valve is the +Y direction; the second direction along the second main surface Sf2 and perpendicular to the +Y direction is the +X direction; and the third direction along the normal to the second main surface Sf2 is the +Z direction. For convenience, support portions 74s, which will be described later, are omitted from illustration in FIGS. 20 and 21.

[0104] The planar light valve serving as the spatial phase modulation element 7 has, for example, a base portion 73 and a plurality of reflecting elements 74.

[0105] The base portion 73 has, for example, a substrate 73s and an electrode (also referred to as a reference electrode) 73e. The substrate 73s may be, for example, a plate-shaped substrate such as a silicon substrate. The reference electrode 73e is located along the second main surface Sf2 of the substrate 73s. The reference electrode 73e may be, for example, a metal film formed on the second main surface Sf2 of the substrate 73s. The reference electrode 73e may be, for example, an electrode provided for each reflective element 74, or may be an electrode common to the multiple reflective elements 74.

[0106] The plurality of reflective elements 74 are arranged in a matrix. More specifically, the plurality of reflective elements 74 are arranged in a matrix on the second main surface Sf2 of the substrate 73s. In the planar light valve, for example, M reflective elements 74 are arranged in the Y direction and N reflective elements 74 are arranged in the X direction. Here, M and N are natural numbers, and each of M and N is, for example, a numerical value ranging from several hundred to several thousand.

[0107] Each of the plurality of reflecting elements 74 includes a movable reflecting portion 74r and a support portion 74s. Here, the plurality of movable reflecting portions 74r in the plurality of reflecting elements 74 function as a plurality of grating elements that reflect the light dispersed by the dispersing element 6. In the examples of Fig. 19 to Fig. 21, each of the plurality of reflecting elements 74 includes a fixed reflecting portion 74f.

[0108] 19 to 21, the fixed reflector 74f is a planar, substantially rectangular member fixed to the substrate 73s, and has a substantially circular opening in the center. The surface of the fixed reflector 74f facing the +Z direction (also referred to as the upper surface) has a light reflecting surface (also referred to as the fixed light reflecting surface) that specularly reflects light.

[0109] The movable reflecting portion 74r has a light reflecting surface (also referred to as a movable light reflecting surface) that specularly reflects light on the side opposite to the base portion 73. The light reflecting surface is a surface parallel to the XY plane. For example, the surface of each movable reflecting portion 74r is configured to be covered with a thin film of metal such as aluminum that specularly reflects light. As a result, for example, the surface of each movable reflecting portion 74r on the side opposite to the base portion 73 functions as a light reflecting surface. Here, for example, since the movable reflecting portion 74r has a light reflecting surface, each movable reflecting portion 74r can reflect light dispersed by the dispersing element 6.

[0110] The support portions 74s are flexible, support the movable reflector 74r at multiple locations, and are connected to the base portion 73. The support portions 74s may be formed, for example, by a fine structure made of an amorphous silicon nitride film or the like. The support portions 74s are formed, for example, by a part of a cross-shaped structure (also referred to as a cross-shaped structure). In this case, the cross-shaped structure has a central portion that forms a part of the -Z direction surface (also referred to as a back surface) of the movable reflector 74r, and four end portions that serve as the support portions 74s that are bridged between the movable reflector 74r and the base portion 73. The surface of the cross-shaped structure is coated with a thin metal film such as aluminum. This thin metal film functions as an electrode (also referred to as a movable electrode). In other words, the movable reflector 74r functions as a movable electrode.

[0111] Here, the movable reflector 74r faces the base portion 73 across a space Sp1. Each movable reflector 74r faces the reference electrode 73e of the base portion 73 across the space Sp1. In other words, the reference electrode 73e of the base portion 73 faces each movable reflector 74r. The support portion 74s supports the movable reflector 74r without contacting the reference electrode 73e, for example. Therefore, for example, bending of the support portion 74s can cause the movable reflector 74r to be displaced relative to the base portion 73, as shown in FIGS. 20 and 21 .

[0112] Here, for example, by applying a potential difference between the movable reflector 74r, which functions as a movable electrode, and the reference electrode 73e, an electrostatic force is generated between the movable reflector 74r and the reference electrode 73e, which attracts the movable reflector 74r to the reference electrode 73e. This electrostatic force causes the support portion 74s to bend.

[0113] The planar light valve as the spatial phase modulation element 7, for example, deflects the support portion 74s by an electrostatic force corresponding to a signal from the first control unit 10, thereby displacing the movable reflecting portion 74r by an amount corresponding to the signal.

[0114] For example, the first control unit 10 can adjust the potential difference applied between the movable reflector 74r and the reference electrode 73e for each of the multiple reflecting elements 74 to deflect the support portion 74s using electrostatic force between the movable reflector 74r and the reference electrode 73e, thereby controlling the displacement of the movable reflector 74r relative to the base portion 73. In other words, the first control unit 10 can control the displacement of the multiple movable reflectors 74r as multiple lattice elements relative to the base portion 73. Note that, for example, after the support portion 74s is deflected by electrostatic force corresponding to the potential difference applied between the movable reflector 74r and the reference electrode 73e, when the potential difference applied between the movable reflector 74r and the reference electrode 73e becomes substantially zero, the elastic force of the support portion 74s returns the support portion 74s to its undeflected reference state. At this time, the displacement of the movable reflector 74r returns to zero.

[0115] Here, the displacement of the movable reflector 74r of each of the plurality of reflecting elements 74 arranged along the Y direction is controlled to be the same. In other words, the displacement of the movable reflector 74r of the plurality of reflecting elements 74 arranged in a matrix is ​​controlled by treating each row of the plurality of reflecting elements 74 arranged along the Y direction as a single unit. Therefore, for example, the planar light valve can function as a blazed diffraction grating by periodically changing the displacement of the movable reflector 74r in the X direction in a manner similar to the second and third states of the grating light valve shown in FIGS. 6 and 7 . The planar light valve as the spatial phase modulator 7 can function as a blazed diffraction grating with a variable grating pitch d and blaze angle θb by controlling the amount of deflection of the plurality of support portions 74s, for example, by controlling the potential applied to the movable electrodes of the plurality of movable reflectors 74r.

[0116] For this reason, for example, the planar light valve serving as the spatial phase modulation element 7 can perform phase modulation on the light dispersed by the spectroscopic element 6 by displacing at least some of the plurality of movable reflecting portions 74r serving as the plurality of grating elements relative to the base portion 73, and can emit diffracted light of some wavelengths within a predetermined wavelength range of the light dispersed by the spectroscopic element 6 along the optical path (incident optical path) Li of the incident light from the spectroscopic element 6 toward the spectroscopic element 6. In this way, the planar light valve serving as the spatial phase modulation element 7 can selectively return light of some wavelengths (also referred to as selected wavelengths) of the light dispersed by the spectroscopic element 6 to the spectroscopic element 6.

[0117] Therefore, even when a planar light valve is applied to the spatial phase modulation element 7, similarly to the first embodiment, by changing the pattern of displacement of the plurality of movable reflecting portions 74r as the plurality of grating elements relative to the base portion 73, it is possible to quickly change the wavelengths (selected wavelengths) of light selectively returned to the spectroscopic element 6 from the light in a predetermined wavelength range dispersed by the spectroscopic element 6. As a result, for example, the wavelength of the output light output from the light source device 100, 100A after multiple amplifications can be quickly switched. Therefore, for example, the wavelength of the light emitted by the light source device 100, 100A can be quickly changed.

[0118] Here, for example, the shape of each of the plurality of movable reflecting portions 74r is not limited to a disk shape, but may be various other plate shapes such as a plate shape with rectangular upper and lower surfaces.

[0119] <<Other variations>> In the first embodiment and each of the modified examples, for example, the depth (= d × tan θb) of the sawtooth pattern of the blazed diffraction grating functionally realized by the spatial phase modulation element 7 does not always have to be set to half the selected wavelength. Here, for example, the depth (= d × tan θb) of the sawtooth pattern of the blazed diffraction grating functionally realized by the spatial phase modulation element 7 may be set to half a specific wavelength within a predetermined wavelength range. The specific wavelength may be, for example, a wavelength at or near the center of the predetermined wavelength range.

[0120] In the first embodiment and each of the modifications described above, for example, the first control unit 10 and the second control unit 20 may be one control unit.

[0121] In the first embodiment and each of the modified examples, for example, some of the functions of the first control unit 10 and the second control unit 20 may be provided in a device external to the light source device 100. For example, a control device 200 or the like may be applied as the external device.

[0122] In the first embodiment and each of the modifications, the location where the optical fiber is provided can be replaced with free space as appropriate, depending on the arrangement of elements before and after it on the optical path.

[0123] It goes without saying that all or part of the components constituting the first embodiment and the various modifications can be combined as appropriate within a range that does not cause contradictions. [Explanation of symbols]

[0124] 1 Optical amplifier 10 First control section 100,100A light source device 2 1st light guiding section 20 Second Control Section 2A 3rd light guide 3. Optical path changing optical system 6. Spectroscopic element 7 Spatial phase modulation element 71,73 Base 71e,73e Reference electrode 71s, 73s board 72 Ribbon 72c connection part 72r reflector 74 Reflective Elements 74r movable reflector 74s support part 8 Second light guide 84 First optical output unit 86 Light guiding part 9A partially reflective optical system E1 1st end surface E2 2nd end face Li incident optical path Sp1 space

Claims

1. an optical amplifier that amplifies and emits light; a spectroscopic element that separates the light emitted from the optical amplifier according to wavelength; a spatial phase modulation element having a base portion and a plurality of grating elements that reflect the light dispersed by the spectroscopic element, wherein at least some of the grating elements are displaced relative to the base portion to perform phase modulation on the light dispersed by the spectroscopic element, and diffracted light of some wavelengths in the wavelength range of the light dispersed by the spectroscopic element is emitted along an incident light path from the spectroscopic element toward the spectroscopic element; a control unit that controls displacement of the plurality of grating elements relative to the base, the diffracted light emitted from the spatial phase modulation element generates light of the part of wavelengths in the spectroscopic element, and the light of the part of wavelengths is amplified by the optical amplifier and then emitted toward the spectroscopic element; outputting light of the part of wavelengths that has been amplified multiple times by the optical amplifier; the plurality of lattice elements includes a plurality of ribbon-shaped portions; Each of the plurality of ribbon-shaped portions has a long, thin ribbon shape extending along a first direction, is flexible, and has a reflecting portion having a light-reflecting surface on a side opposite to the base portion, the plurality of ribbon-shaped portions are aligned along a second direction perpendicular to the first direction, the reflecting portion of each of the plurality of ribbon-shaped portions faces the base portion across a space, each of the plurality of ribbon-shaped portions includes a connecting portion connected to the base portion at each of both ends in the first direction; the base portion includes an electrode facing each of the reflecting portions; the control unit adjusts a potential difference applied between the reflecting portion of each of the plurality of ribbon-shaped portions and the electrode to control an amount of deflection of the plurality of ribbon-shaped portions due to an electrostatic force between the reflecting portion of each of the plurality of ribbon-shaped portions and the electrode, thereby controlling an amount of displacement of the reflecting portion of each of the plurality of ribbon-shaped portions with respect to the base portion; the spectroscopic element emits the light emitted from the optical amplifier in the second direction at different angles according to the wavelength, and irradiates the light on the reflecting portions of the plurality of ribbon-shaped portions; the control unit controls the amount of bending of the plurality of ribbon-shaped portions to cause at least some of the plurality of ribbon-shaped portions to function as blazed diffraction gratings; an angle formed by the light of the certain wavelengths incident on the blazed diffraction grating from the spectroscopic element with respect to the blazed diffraction grating is the same as an angle formed by the diffracted light of the certain wavelengths emitted from the blazed diffraction grating with respect to the blazed diffraction grating.

2. The light source device according to claim 1 , The light source device, wherein the optical amplifier includes a semiconductor optical amplifier, a booster optical amplifier, or a semiconductor laser.

3. 3. The light source device according to claim 1, The light source device, wherein the spectroscopic element includes a diffraction grating.

4. The light source device according to any one of claims 1 to 3, The control unit switches the state in which the portion of the wavelengths includes a first wavelength to a state in which the portion of the wavelengths includes a second wavelength different from the first wavelength by changing the displacement pattern of the plurality of grating elements relative to the base portion from a first pattern to a second pattern using the spatial phase modulation element.

5. The light source device according to any one of claims 1 to 3, A light source device, wherein the part of wavelengths includes a plurality of different wavelengths that are spaced apart from each other.

6. The light source device according to claim 5 , the control unit changes the displacement pattern of the plurality of grating elements relative to the base portion from a first pattern to a second pattern using the spatial phase modulation element, thereby switching from a state in which the plurality of wavelengths include a first A wavelength and a first B wavelength to a state in which the plurality of wavelengths include a second A wavelength different from the first A wavelength and a second B wavelength different from the first B wavelength.

7. The light source device according to any one of claims 1 to 6, a first light guiding unit, an optical path changing optical system, and a second light guiding unit; the first light guiding section guides the light emitted from the optical amplifier toward the optical path changing optical system, the optical path changing optical system guides the light emitted from the optical amplifier and passed through the first light guiding section toward the spectroscopic element, and guides the light of the part of wavelengths generated by the spectroscopic element in accordance with the diffracted light emitted from the spatial phase modulation element to the second light guiding section; the second light guiding section includes: a first light output section that outputs a portion of the light guided to the second light guiding section by the optical path changing optical system to the outside of the second light guiding section; and a light guiding section that guides the remaining light, excluding the portion of the light, guided to the second light guiding section by the optical path changing optical system, toward the optical amplifier.

8. The light source device according to any one of claims 1 to 6, a third light guiding unit that guides the light emitted from a first end face of the optical amplifier toward the spectroscopic element and guides the light of the part of wavelengths generated by the spectroscopic element in accordance with the diffracted light emitted from the spatial phase modulation element toward the first end face of the optical amplifier; a partially reflective optical system that transmits a portion of the light emitted from the second end face of the optical amplifier and outputs the remaining light, excluding the portion of the light, emitted from the second end face of the optical amplifier, toward the second end face.

9. An optical amplifier that amplifies and emits light; a spectroscopic element that separates the light emitted from the optical amplifier according to wavelength; a spatial phase modulation element having a base portion and a plurality of grating elements that reflect the light dispersed by the spectroscopic element, wherein at least some of the grating elements are displaced relative to the base portion to perform phase modulation on the light dispersed by the spectroscopic element, and diffracted light of some wavelengths in the wavelength range of the light dispersed by the spectroscopic element is emitted along an incident light path from the spectroscopic element toward the spectroscopic element; a control unit that controls displacement of the plurality of grating elements relative to the base, the diffracted light emitted from the spatial phase modulation element generates light of the part of wavelengths in the spectroscopic element, and the light of the part of wavelengths is amplified by the optical amplifier and then emitted toward the spectroscopic element; outputting light of the part of wavelengths that has been amplified multiple times by the optical amplifier; the spatial phase modulation element includes a plurality of reflective elements arranged in a matrix; each of the plurality of reflective elements includes a movable reflective portion that faces the base portion across a space and has a light-reflecting surface on the opposite side to the base portion, and a flexible support portion that supports each of a plurality of points of the movable reflective portion and is connected to the base portion; the plurality of grating elements includes the movable reflective portion of each of the plurality of reflective elements; the base portion includes an electrode facing each of the movable reflective portions; the control unit adjusts a potential difference applied between the movable reflector and the electrode in each of the plurality of reflecting elements to control a deflection amount of the support unit due to an electrostatic force between the movable reflector and the electrode, thereby controlling a displacement amount of the movable reflector with respect to the base unit; The plurality of reflective elements are arranged in a matrix, with M reflective elements (M is a natural number) arranged in a first direction and N reflective elements (N is a natural number) arranged in a second direction, the spectroscopic element emits the light emitted from the optical amplifier in the second direction at different angles according to the wavelength, and irradiates the light on the movable reflecting portions of the plurality of reflecting elements; the control unit controls a displacement amount of the movable reflecting portion of each of the plurality of reflecting elements relative to the base portion, thereby causing at least a portion of the plurality of reflecting elements to function as a blazed diffraction grating; an angle formed by the light of the certain wavelengths incident on the blazed diffraction grating from the spectroscopic element with respect to the blazed diffraction grating is the same as an angle formed by the diffracted light of the certain wavelengths emitted from the blazed diffraction grating with respect to the blazed diffraction grating.

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