Self-injection-locked laser device and molecular information output device

Abstract

Provided is a self-injection locking type laser device in which variations in environmental changes, optical path length, and resonator length are less likely to occur. The self-injection locking type laser device includes a first base plate, a second base plate, a temperature adjustment element disposed between the first base plate and the second base plate, a semiconductor laser light source disposed on the first base plate, a reference resonator disposed on the first base plate, located on an optical path of laser light emitted from the semiconductor laser light source, and including at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser light source, a first cover covering the semiconductor laser light source and the reference resonator and in contact with the first base plate, and a second cover covering the first cover and in contact with the second base plate.

Description

Technical Field

[0001] This disclosure relates to a self-injection locking laser device and a molecular information output device. Background Technology

[0002] For example, Patent Document 1 discloses an optical module that includes a semiconductor laser element and a housing, which can lock the laser wavelength emitted from the semiconductor laser element.

[0003] <Prior art documents>

[0004] <Patent Documents>

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-68407 Summary of the Invention

[0006] <Problem to be solved by this invention>

[0007] The purpose of this disclosure is to provide a self-injection locked laser device that is less susceptible to environmental changes and has reduced variations in optical path length and resonator length.

[0008] <Methods for solving problems>

[0009] A self-injection locking laser device according to one embodiment of this disclosure includes: a first base plate; a second base plate; a temperature adjustment element disposed between the first base plate and the second base plate; a semiconductor laser source disposed on the first base plate; a reference resonator disposed on the first base plate, located in the optical path of the laser emitted from the semiconductor laser source, and including at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser source; a first cover covering the semiconductor laser source and the reference resonator, and in contact with the first base plate; and a second cover covering the first cover and in contact with the second base plate.

[0010] Another embodiment of the self-injection locking laser device disclosed herein includes: a first substrate including a recess; a second substrate; a temperature adjustment element disposed between the first substrate and the second substrate; a semiconductor laser source disposed in the recess of the first substrate; a reference resonator disposed in the recess of the first substrate, located in the optical path of the laser emitted from the semiconductor laser source, and including at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser source; a first cover covering the semiconductor laser source and the reference resonator, and in contact with the first substrate; and a second cover covering the first cover and in contact with the second substrate.

[0011] <The Effects of the Invention>

[0012] According to embodiments of this disclosure, a self-injection locking laser device that is less susceptible to environmental changes and exhibits reduced variations in optical path length and resonator length can be provided. Attached Figure Description

[0013] Figure 1 This is a schematic top view of the self-injection locking laser device according to the first embodiment.

[0014] Figure 2 yes Figure 1 A schematic cross-sectional view of line II-II in the diagram.

[0015] Figure 3A yes Figure 1 A schematic cross-sectional view of line IIIA-IIIA in the diagram.

[0016] Figure 3B This is a block diagram showing the hardware structure of the control unit of the self-injection locking laser device according to the first embodiment.

[0017] Figure 3C This is a block diagram showing the functional structure of the controller of the self-injection locking laser device according to the first embodiment.

[0018] Figure 3D This is a flowchart illustrating the process performed by the controller of the self-injection locking laser device of the first embodiment.

[0019] Figure 4 This is a schematic top view of the self-injection locking laser device according to the second embodiment.

[0020] Figure 5 yes Figure 4 A schematic cross-sectional view of the VV line.

[0021] Figure 6 This is a schematic top view showing the first example of the self-injection locking laser device according to the third embodiment.

[0022] Figure 7 yes Figure 6 A schematic cross-sectional view of line VII-VII in the diagram.

[0023] Figure 8 This is a schematic top view showing a second example of the self-injection locking laser device according to the third embodiment.

[0024] Figure 9 This is a schematic top view of the self-injection locking laser device of Variation Example 1.

[0025] Figure 10 This is a schematic top view of the self-injection locking laser device of Variation Example 2.

[0026] Figure 11 This is a schematic cross-sectional view of the molecular information output device according to the fourth embodiment. Detailed Implementation

[0027] The self-injection-locked laser device and molecular information output device according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following description is intended to illustrate the self-injection-locked laser device and molecular information output device that specifically demonstrate the technical concept of the present disclosure, but is not limited thereto. Hereinafter, the self-injection-locked laser device will also be abbreviated as SIL-LD device.

[0028] Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the constituent parts described in the embodiments are not intended to limit the scope of this disclosure, but are merely illustrative examples. Additionally, since the accompanying drawings are schematic representations of the embodiments, the proportions, spacing, or positional relationships of the components are sometimes exaggerated, or sometimes parts of the components are omitted. Furthermore, in the following description, the same names and symbols denote components of the same or similar nature, and detailed descriptions may be appropriately omitted. As sectional views, end views showing only the cross-section are sometimes used.

[0029] In the accompanying figures, orthogonal coordinates including the X, Y, and Z axes are used to represent directions. The X, Y, and Z axes are orthogonal to each other. The direction indicated by the arrow in the X direction is the +X direction, and the direction opposite to the +X direction is the -X direction. The direction indicated by the arrow in the Y direction is the +Y direction, and the direction opposite to the +Y direction is the -Y direction. The direction indicated by the arrow in the Z direction is the +Z direction, and the direction opposite to the +Z direction is the -Z direction. However, the orientation of the SIL-LD device and molecular information output device in the embodiments is not limited to these settings; the orientation of the SIL-LD device and molecular information output device in the embodiments is arbitrary.

[0030] In the terminology of the embodiments, a top view refers to a view of the object as seen from the +Z direction. In the description of the embodiments, to illustrate the internal structure of the SIL-LD device of the embodiment, a top view that allows a view through the interior of the first and second covers of the SIL-LD device is sometimes used. In the embodiments shown below, "along the X, Y, and Z axes" means that the object has an inclination relative to these axes within the range of ±15°, ±10°, or preferably ±5°. The positional relationship expressed as "above" in this specification also includes both contact and non-contact situations where the object is positioned above.

[0031] [First Implementation]

[0032] <Structure of the SIL-LD device in the first embodiment>

[0033] Reference Figures 1 to 3A This describes the SIL-LD device of the first embodiment. Figure 1 This is a schematic diagram showing an example of the SIL-LD device 100 of the first embodiment. Figure 2 yes Figure 1 A schematic cross-sectional view of line II-II in the diagram. Figure 3A yes Figure 1 A schematic cross-sectional view of lines IIIA-IIIA in the diagram. Here, in Figures 1 to 3A In the diagram, a portion of each of the lasers M1 to M6 passing through the SIL-LD device 100 is indicated by an arrow. Additionally, in... Figures 1 to 3A In the SIL-LD device 100, the optical path P through which lasers M1 to M6 pass is represented by a dashed line.

[0034] like Figures 1 to 3A As shown, the SIL-LD device 100 includes a first base plate 1, a second base plate 2, a temperature adjustment element 3 disposed between the first base plate 1 and the second base plate 2, and a semiconductor laser source 4 disposed on the first base plate 1. Additionally, the SIL-LD device 100 includes a reference resonator 5 located on the first base plate 1 and on the optical path P of the laser M1 emitted from the semiconductor laser source 4, which includes at least a first mirror 51 and a second mirror 52 for providing optical feedback to the semiconductor laser source 4. Furthermore, the SIL-LD device 100 includes a first cover 7 covering the semiconductor laser source 4 and the reference resonator 5 and in contact with the first base plate 1, and a second cover 8 covering the first cover 7 and in contact with the second base plate 2.

[0035] exist Figures 1 to 3A In the example shown, the SIL-LD device 100 includes a first collimating lens 9 that transmits a laser M1 emitted from a semiconductor laser source 4, and a beam splitter 10 that transmits a portion of the laser M1 that has been transmitted through the first collimating lens 9 and reflects the remainder of the laser M1. Additionally, in Figures 1 to 3A In the example shown, the SIL-LD device 100 includes an optical isolator 11 located between the first cover 7 and the second cover 8 and on the optical path P, and a focusing lens 12 that transmits the laser M3 reflected by the beam splitter 10. Additionally, in Figure 2 In the example shown, temperature sensor 13 is embedded in the first base plate 1. Additionally, in Figure 2 In the example shown, a position adjustment element 21 for moving the beam splitter 10 may also be included.

[0036] exist Figure 1In the example shown, the laser M3, after being reflected by the beam splitter 10 and transmitted through the focusing lens 12, is incident on the reference resonator 5. The laser M3 incident on the reference resonator 5 is reflected by the first mirror 51 and the second mirror 52 respectively, and resonates back and forth between the first mirror 51 and the second mirror 52. Figure 1 The arrow representing laser M4 illustrates the laser traveling back and forth between the first mirror 51 and the second mirror 52. A portion of laser M4, during this back-and-forth motion, exits from the reference resonator 5 towards the condenser lens 12. Laser M5, exiting from the reference resonator 5, passes through the condenser lens 12 and then enters the beam splitter 10. A portion of laser M5 entering the beam splitter 10 is reflected by the beam splitter 10 and exits towards the semiconductor laser source 4. Laser M6, as a portion of laser M5 reflected by the beam splitter 10, passes through the first collimating lens 9 and then enters the semiconductor laser source 4, providing feedback on the optical frequency of laser M1.

[0037] When the difference between the optical frequency of the laser M1 emitted from the semiconductor laser source 4 and the resonant frequency of the reference resonator 5, determined by the resonator length Lc, is close to less than half the full width at half maximum (FWHM) of the linewidth of the reference resonator 5, the laser M1 enters the reference resonator 5 and undergoes a round trip to filter the optical frequency. The filtered light, becoming thinner than the original linewidth, is fed back to the semiconductor laser source 4. This optical feedback by the laser M1 results in a self-injection locking linewidth narrowing effect. The linewidth of the self-injection locked laser can, for example, be between 500 Hz and 1 MHz. The oscillation frequency of the self-injection locked laser is almost identical to the resonant frequency of the reference resonator 5. However, if the deviation between the optical frequency of the laser M1 emitted from the semiconductor laser source 4 and the resonant frequency of the reference resonator 5 is large, the linewidth of the laser Mo extracted from the SIL-LD device 100 will become equal to the linewidth of the laser M1 emitted from the semiconductor laser source 4. The laser M1 emitted from the semiconductor laser source 4 does not resonate with the reference resonator 5, and therefore self-injection locking does not occur. In this case, the linewidth of the laser Mo extracted from the SIL-LD device 100 will not be narrower relative to the linewidth of the laser M1.

[0038] To reduce the linewidth of the laser Mo extracted from the SIL-LD device 100, the optical path length Lb between the first end face 41 of the semiconductor laser element 401 of the semiconductor laser source 4 and the first face 511 of the reference resonator 5 needs to be λ×(N+θ) / 2, and the resonator length Lc of the reference resonator 5 needs to be λ×M / 2. The optical path length Lb represents the length of the optical feedback path in self-injection locking. Figure 1In this context, the sum of Lb1 and Lb2 is equivalent to Lb. Here, λ is the wavelength of the laser Mo, N and M are positive integers, and θ is a constant inherent to the semiconductor laser element 401. However, when environmental changes such as temperature, air pressure, humidity, or convection cause at least one of the optical path length Lb and the resonator length Lc to change by a factor of λ / 2, the above condition cannot be met, and the linewidth of the laser Mo will not become thinner.

[0039] In this embodiment, the semiconductor laser source 4 and the reference resonator 5 are protected from environmental changes within the SIL-LD device 100 by the first base plate 1 and the first cover 7, and the changes in the optical path length Lb and the resonator length Lc are reduced. This stabilizes the state where the linewidth of the laser Mo becomes thinner due to self-injection locking. Furthermore, the operation of the temperature adjustment element 3 is controlled based on the temperature of the semiconductor laser source 4 detected by the temperature sensor 13. The temperature of the first base plate 1 remains constant, and the temperature of the first cover 7, which is in contact with the first base plate 1, is also close to the temperature of the first base plate 1. Therefore, the semiconductor laser source 4 and the reference resonator 5, surrounded by the first base plate 1 and the first cover 7, are less susceptible to environmental changes, and the variations in the optical path length Lb and the resonator length Lc are reduced.

[0040] The following is a detailed description of the various elements constituting the SIL-LD device 100.

[0041] (First base plate 1 and second base plate 2)

[0042] exist Figures 1 to 3A In the example shown, the first base plate 1 is disposed on the second base plate 2 via a temperature adjustment element 3. Here, as long as the temperature adjustment element 3 is disposed between the first base plate 1 and the second base plate 2, the positional relationship between the first base plate 1 and the second base plate 2 can be arbitrary. The first base plate 1 can be disposed on the second base plate 2 via the temperature adjustment element 3 in either the X or Y direction.

[0043] The materials of the first substrate 1 and the second substrate 2 may include at least one selected from the group consisting of aluminum, copper, graphite, diamond, aluminum nitride, super Invar alloy, and low thermal expansion glass. When the materials of the first substrate 1 and the second substrate 2 are aluminum, copper, graphite, diamond, or aluminum nitride, heat dissipation from the substrate can be improved. Furthermore, when the materials of the first substrate 1 and the second substrate 2 are super Invar alloy or low thermal expansion glass, the changes in the optical path length Lb and the resonator length Lc caused by thermal expansion can be reduced. The materials of the first substrate 1 and the second substrate 2 may be the same or different. Preferably, the SIL-LD device 100 has the first substrate 1 made of a material with low thermal expansion and the second substrate 2 made of a material with high thermal conductivity. This allows for effective heat dissipation through the second substrate 2, making it easier to maintain a constant temperature for the first substrate 1. Furthermore, when the temperature of the first substrate 1 remains constant, the change in the optical path length Lb is reduced due to the low thermal expansion of the first substrate 1. The combination of the first base plate 1 and the second base plate 2, for example, the first base plate 1 can be super Invar alloy and the second base plate 2 can be copper.

[0044] (Temperature adjustment element 3)

[0045] Temperature adjustment element 3 is disposed between the first base plate 1 and the second base plate 2. Temperature adjustment element 3 is, for example, adhered to the first base plate 1 and the second base plate 2 respectively by an adhesive. The adhesive may be, for example, thermal grease. Figures 1 to 3A In the example shown, the temperature adjustment element 3 includes a Peltier element. By adjusting the temperature of the first substrate 1 using the Peltier element, the temperature of the first substrate 1 is kept constant. Here, "keeping the temperature constant" means that the temperature of the first substrate 1 varies within a range of ±1°C, preferably ±0.01°C, or more preferably ±0.001°C relative to a predetermined temperature. However, the temperature adjustment element 3 is not limited to a Peltier element as long as it is positioned between the first substrate 1 and the second substrate 2 and can adjust the temperature. The SIL-LD device 100 reduces the temperature rise of the first substrate 1 by utilizing the temperature adjustment element 3, thereby reducing the change in the optical path length Lb caused by the thermal expansion of the first substrate 1. In addition, by keeping the temperature of the first substrate constant, the expansion or contraction of the reference resonator 5 can be reduced, and the variation in the resonator length Lc can be reduced. The temperature adjustment element 3 can be arranged overlapping the semiconductor laser source 4 and the reference resonator 5 in a top view. Thus, by keeping the temperature of the first substrate 1 constant, the temperature variation of the semiconductor laser source 4 and the reference resonator 5 can be reduced.

[0046] (Semiconductor laser source 4)

[0047] exist Figure 1In the example shown, the semiconductor laser source 4 includes a semiconductor laser element 401 and a package 402 for sealing the semiconductor laser element 401. A base may also be provided between the semiconductor laser element and the package. The interior of the package 402 is sealed with dry air or an inert gas. This reduces the possibility of photodust accumulation, thereby reducing the degradation of the semiconductor laser element 401. Sealing the interior of the package 402 is more preferable when the oscillation wavelength of the semiconductor laser element 401 is shorter, for example, below 550 nm, below 500 nm, or below 450 nm. This is because the light energy density at the first end face 41 of the semiconductor laser element 401 increases.

[0048] The semiconductor laser element 401 includes a first end face 41 and a second end face 42. The semiconductor laser element 401 emits a laser beam M1 from the first end face 41. The wavelength band of the laser beam M1 emitted from the semiconductor laser element 401 is, for example, 360 nm to 1600 nm, preferably 400 nm to 550 nm. Furthermore, the linewidth (frequency) of the laser beam M1 emitted solely from the semiconductor laser element 401 is, for example, 10 MHz to 1 GHz. The linewidth value is not limited to this example and may be less than 10 MHz. Through self-injection locking, the linewidth of the light extracted from the SIL-LD device 100 can be further reduced. Figure 1 The SIL-LD device 100 shown has a structure in which self-injection locking and light extraction are performed on the side where the first end face 41 of the semiconductor laser element 401 is located.

[0049] exist Figures 1 to 3A In the example shown, the semiconductor laser source 4 includes a distributed feedback laser diode (DFB-LD) element. When the semiconductor laser source 4 includes a DFB-LD element, the laser M1 emitted from the semiconductor laser source 4 becomes a single frequency, and the laser Mo extracted from the SIL-LD device 100 can also become a single frequency and linewidth.

[0050] DFB-LD devices can include materials such as those from group III-V. For example, DFB-LD devices can be nitride semiconductors, arsenide semiconductors, or phosphide semiconductors. A DFB-LD device can be, for example, a stack comprising an n-side cladding layer, an n-side light guiding layer, an active layer, a p-side light guiding layer, and a p-side cladding layer, forming an optical waveguide. Either the n-side cladding layer or the n-side light guiding layer includes at least one n-type semiconductor layer. The active layer can be a quantum well. Either the p-side light guiding layer or the p-side cladding layer includes at least one p-type semiconductor layer. A DFB-LD device can have a diffraction grating in at least a portion within the waveguide. The period of the diffraction grating is λ / (2×n). eqλ is the oscillation wavelength of the laser M1 in the semiconductor laser element, and n eq It is the equivalent refractive index. In this example, the order is 1.

[0051] exist Figures 1 to 3A In the example shown, the first end face 41 of the DFB-LD element is covered by an anti-reflective film 410. The reflectivity of the anti-reflective film 410 to the laser wavelength can be, for example, between 0.01% and 1%. By covering the end face with the anti-reflective film 410, the DFB-LD element can obtain stable single-mode characteristics. The second end face 42 is covered by a high-reflectivity film 420. The reflectivity of the high-reflectivity film to the laser wavelength can be, for example, between 90% and 99.9%.

[0052] exist Figures 1 to 3A In the example shown, the diffraction grating of the DFB-LD element has a λ / 4 phase shift structure. A λ / 4 phase shift structure means that, for example, the phase of the diffraction grating of the DFB-LD element is shifted to one-quarter of the peak wavelength of the laser emitted by the DFB-LD element. By having a λ / 4 phase shift structure, the DFB-LD element can achieve stable single-mode characteristics.

[0053] The semiconductor laser source 4 is not limited to DFB-LD elements. For example, the semiconductor laser source 4 may include semiconductor laser elements other than DFB-LD elements. For example, it may include distributed Bragg reflector (DBR) laser elements or photonic crystal surface-emitting lasers (PCSELs).

[0054] (Reference Resonator 5)

[0055] exist Figure 1 In the reference resonator 5 shown, the first mirror 51 includes a first surface 511 serving as the light-reflecting surface of the reference resonator 5 and a second surface 512 located opposite to the first surface 511. The second mirror 52 includes a third surface 513 opposite to the first surface 511 and a fourth surface 514 located opposite to the third surface 513. The third surface 513 is the light-reflecting surface of the reference resonator 5. The reflectivity of the first mirror 51 for the wavelength of the laser M1 emitted from the semiconductor laser source 4 is, for example, 95.0% to 99.9%. Similarly, the reflectivity of the second mirror 52 for the wavelength of the laser M1 emitted from the semiconductor laser source 4 is, for example, 95.0% to 99.9%. The first mirror 51 and the second mirror 52 in the reference resonator 5 may be constructed using materials such as synthetic quartz or low-thermal-expansion glass.

[0056] The resonator length Lc of the reference resonator 5 is equivalent to the distance between the first mirror 51 and the second mirror 52. More specifically, in Figure 1 In the example shown, the resonator length Lc of the reference resonator 5 is equivalent to the distance between the first surface 511 of the first mirror 51 and the third surface 513 of the second mirror 52. As an example, the resonator length Lc is 10 mm, but it is not limited to this. It can be appropriately changed according to the desired frequency of the laser Mo. Figure 1 The reference resonator 5 shown is slightly tilted relative to the optical axis of the laser M3. Therefore, the reflected light from the second surface 512 of the first mirror 51 is difficult to return as return light to the semiconductor laser source 4. Figure 1 In the middle, because the reference resonator 5 is tilted, the light that resonates with the reference resonator 5 will resonate in the V-shaped optical path.

[0057] exist Figures 1 to 3A In the reference resonator 5 shown, the first mirror 51 and the second mirror 52 are both concave mirrors. Additionally, in... Figures 1 to 3A In the example shown, the first mirror 51 and the second mirror 52 constitute a confocal resonator. That is, the radii of curvature of the first mirror 51 and the second mirror 52 are equal, and the distance between the first mirror 51 and the second mirror 52 is equal to the size of the radii of curvature. Therefore, the fundamental mode and higher-order modes resonating in the reference resonator 5 are dimensionally reduced and resonate at the same frequency. The confocal resonator has a simple spectral structure through mode dimension reduction. In addition, the mode of the light extracted from the reference resonator 5 depends on the mode of the light resonating in the reference resonator 5. Therefore, if the laser of the fundamental mode is resonated by the reference resonator 5, the light of the fundamental mode can be extracted and fed back to the semiconductor laser element 401. Therefore, the confocal resonator is suitable for mode observation of the laser Mo extracted from the SIL-LD device 100, etc.

[0058] The reference resonator 5 is not limited to being composed of a first mirror 51 and a second mirror 52, and may include three or more mirrors. For example, the reference resonator 5 may also include mirrors arranged in a V-shape or bow-tie shape. Additionally, the reference resonator 5 may include an etalon. When the reference resonator 5 includes an etalon, the first mirror 51 corresponds to the side near the front, i.e., the side where the condenser lens 12 is located, and the second mirror 52 corresponds to the side at the depth, i.e., the opposite side of the side where the condenser lens 12 is located. The first mirror 51 and the second mirror 52 of this etalon may also constitute a confocal resonator. Furthermore, the reference resonator 5 is not limited to a confocal resonator. Moreover, the first mirror 51 and the second mirror 52 are not limited to concave mirrors, and may also be two or more opposing plane mirrors, etc.

[0059] The SIL-LD device 100, as described above, includes a semiconductor laser source 4 and a reference resonator 5. As described above, the frequency of the laser light M1 emitted from the semiconductor laser source 4 is filtered by the reference resonator 5. This filtered light, with a finer linewidth than before, is fed back to the semiconductor laser source 4. As a result of this optical feedback, the laser M1 is self-injected and locked, and the linewidth of the laser M1 becomes finer, achieving a predetermined linewidth.

[0060] The optical path length Lb of the resonator formed by the first end face 41 of the semiconductor laser source 4 and the first face 511 of the first mirror 51 required for optical feedback is equivalent to the sum of lengths Lb1 and Lb2. Figure 1 In the example shown, the lengths are the sum of lengths Lb1 and Lb2. Length Lb1 is the length corresponding to the distance from the first end face 41 of the semiconductor laser source 4 to the approximate center of the beam splitter 10. Length Lb2 is the length corresponding to the distance from the approximate center of the beam splitter 10 to the first surface 511 of the first mirror 51 in the reference resonator 5.

[0061] The first surface 511 of the first mirror 51, which is opposite to the second mirror 52, is a shared structure in both the optical path length Lb and the resonator length Lc.

[0062] (First Cover 7)

[0063] The first cover 7 covers the semiconductor laser source 4 and the reference resonator 5 and is in contact with the first base plate 1. Therefore, the first cover 7 and the first base plate 1 are in thermal contact, and when the semiconductor laser source 4 is driven, the temperature of the first cover 7 is close to the temperature of the first base plate 1. Thus, since the semiconductor laser source 4 and the reference resonator 5 are disposed within the space enclosed by the first cover 7 and the first base plate 1, environmental changes are less likely to occur within this space, and the semiconductor laser source 4 and the reference resonator 5 are less susceptible to the effects of environmental changes.

[0064] Furthermore, by sealing with the first cover 7, the environment of the space sealed by the first cover 7 is easily stabilized, extending the time that the laser M1 can maintain its frequency after resonance with the reference resonator 5. The semiconductor laser source 4 and the reference resonator 5 are sealed by the first base plate 1 and the first cover 7. For example, an O-ring or gasket can be placed between the first cover 7 and the first base plate 1 in the first cover 7 to effectively seal the semiconductor laser source 4 and the reference resonator 5.

[0065] When the semiconductor laser source 4 is driven and the temperature of the first base plate 1 remains constant, the absolute value of the temperature difference between the first cover 7 and the first base plate 1 is, for example, greater than 0°C and less than 1°C, preferably greater than 0°C and less than 0.1°C, more preferably greater than 0°C and less than 0.001°C. The first cover 7 can be fixed to the first base plate 1 by screws. The screws are tightened, for example, through the side wall of the first cover 7. The first cover 7 can also be fused to the first base plate 1 or bonded by adhesive. Considering maintainability, it is preferable to fix the first cover 7 to the first base plate 1 using screws. The size and shape of the first cover 7 can be appropriately determined. Figure 2 In the example shown, the laser M2, transmitted through the beam splitter 10, exits from the inside of the first cover 7 to the outside through the first opening 71 formed on the first cover 7. The material of the first cover 7 includes aluminum or copper. Heat from the first base plate 1 is effectively transferred to the first cover 7, causing the temperature of the first cover 7 to easily approach the temperature of the first base plate 1. The first cover 7 can also be a composite material in which heat-insulating materials such as foam resin are adhered to the outside of the aluminum or copper. This reduces the influence of temperature on the outside of the first cover 7. A light-transmitting component 710, such as synthetic quartz, can be inserted into the first opening 71.

[0066] (Second cover 8)

[0067] The second cover 8 covers the first cover 7 and contacts the second base plate 2. The second cover 8 can be fixed to the second base plate 2 by screws. The screws are tightened, for example, through the side wall of the second cover 8. The second cover 8 can be fused to the second base plate 2 or glued by adhesive. Considering maintainability, it is preferable to fix the second cover 8 to the second base plate 2 by screws. The second cover 8 protects the first cover 7 and the first base plate 1 from the external environment of the SIL-LD device 100. This makes the spatial environment enclosed by the first cover 7 and the first base plate 1 more stable. The size and shape of the second cover 8 can be appropriately determined. The laser M2, which has been transmitted through the optical isolator 11, is emitted as laser Mo from the inside of the second cover 8 to the outside through the second opening 81 formed on the second cover 8. The material of the second cover 8 includes aluminum or copper. Alternatively, the second cover 8, like the first cover 7, can also be a composite material with further heat-insulating material bonded to it. A light-transmitting component 810, such as synthetic quartz, can also be inserted into the second opening 81.

[0068] The first cover 7 covers the components that help determine the optical path length Lb and the resonator length Lc. On the other hand, the second cover 8 covers the first cover 7 and the components used to control the self-injection locking laser. As a result, the number and volume of the components covered by the first cover 7 are reduced, and the first cover 7 can be reduced in size. By reducing the size of the first cover 7, the temperature unevenness of the first cover 7 is reduced, thereby reducing the temperature difference between the first cover 7 and the first base plate 1.

[0069] (First collimating lens 9)

[0070] The first collimating lens 9 can be any type of lens, such as a spherical lens or an aspherical lens. The first collimating lens 9 can be composed of a combination of two or more lenses. The first collimating lens 9 can be made of materials such as glass, quartz, synthetic quartz, sapphire, or transparent ceramic.

[0071] (Band splitter 10)

[0072] Beam splitter 10 can use an optical element with a specified reflectivity and transmittance for the peak wavelength of the laser M1 emitted from semiconductor laser source 4. The transmittance of the beam splitter can be, for example, 50% to 80% or 65% to 75%. Beam splitter 10 can be plate-shaped or cubic.

[0073] (Optical Isolator 11)

[0074] exist Figure 1 In the example shown, the optical isolator 11 is located between the first cover 7 and the second cover 8, and is situated on the optical path P. Alternatively, the optical isolator 11 is located outside the first cover 7 and inside the second cover 8, and is situated on the optical path P. The optical isolator 11 has a structure that clamps a Faraday rotor between two polarizers. The optical isolator 11 can be a structure combining a polarization beam splitter and a λ / 4 wavelength plate. By incorporating the optical isolator 11, the SIL-LD device 100 can reduce the possibility of the laser Mo emitted from the SIL-LD device 100 being reflected or scattered outside the SIL-LD device 100, thus reducing the possibility of it becoming return light incident on the SIL-LD device 100. This reduces the instability of the single-mode characteristics of the SIL-LD device 100 caused by the return light of the laser Mo. The optical isolator 11 can be positioned outside the SIL-LD device 100 as needed.

[0075] In addition, various optical components such as mirrors, lenses, beam shaping elements, electro-optic modulators or acousto-optic modulators can be configured on the optical path P between the first cover 7 and the second cover 8, in addition to the optical isolator 11.

[0076] (Condensing Lens 12)

[0077] The condenser lens 12 can be any type of lens, such as a spherical lens or an aspherical lens. The condenser lens 12 can be composed of a combination of two or more lenses. The condenser lens 12 can be made of materials such as glass, quartz, synthetic quartz, sapphire, or transparent ceramic.

[0078] (Temperature sensor 13)

[0079] The temperature sensor 13 is embedded in the first bottom plate 1 and can detect the temperature of the first bottom plate 1. The temperature sensor 13 can be composed of a thermistor, a thermocouple, a platinum sensor, etc. The SIL-LD device 100 controls the operation of the temperature adjustment element 3 according to the temperature of the first bottom plate 1 detected by the temperature sensor 13, so as to keep the temperature of the first bottom plate 1 constant. By keeping the temperature of the first bottom plate 1 constant, the SIL-LD device 100 can reduce the variation of the optical path length Lb caused by the thermal expansion of the first bottom plate 1, etc. In addition, the temperature sensor 13 is embedded in the first bottom plate 1 directly below the semiconductor laser light source 4. Thus, the temperature of the semiconductor laser light source 4 can be controlled with higher precision, and the variation of the resonator length of the semiconductor laser element caused by temperature changes can be reduced.

[0080] (Optical detector 55)

[0081] The optical detector 55 is disposed on the opposite side of the first mirror 51 across the fourth surface 514 of the second mirror 52 included in the reference resonator 5. The optical detector 55 detects the signal intensity of the light transmitted through the second mirror 52. When the oscillation frequency of the semiconductor laser light source 4 approaches the resonance frequency of the reference resonator 5, the laser resonates with the reference resonator 5, so a part of the laser is also transmitted through the second mirror 52. By detecting this transmitted light with the optical detector 55, the operation of self-injection locking can be confirmed. The optical detector 55 can be, for example, a photodiode.

[0082] (Position adjustment element 21)

[0083] The position adjustment element 21 is an element that adjusts the optical path length Lb by moving the beam splitter 10. The position adjustment element 21 can, for example, move the beam splitter 10 in the normal direction of the reflection surface of the beam splitter 10. The position adjustment element 21 can be, for example, a piezoelectric element. The position adjustment element 21 is directly or indirectly disposed on the first bottom plate 1 in a manner that enables the beam splitter 10 to move. The position adjustment element 21 is composed of, for example, lead zirconate titanate. The position adjustment element 21 expands and contracts in the normal direction of the reflection surface of the beam splitter 10 according to the applied drive voltage, so as to be able to move the beam splitter 10 in the normal direction of the reflection surface of the beam splitter 10. However, the actuator for moving the beam splitter 10 is not limited to a piezoelectric actuator, and can also be an electrostatic actuator, a thermal actuator, etc.

[0084] <Relocking function of the SIL-LD device 100>

[0085] In the SIL-LD device, changes in internal or external temperature or air pressure can cause variations in the optical path length Lb, the resonator length Lc of the reference resonator 5, etc., which may lead to a situation where the self-injection lock state is lost. If the self-injection lock state is lost, the linewidth of the laser Mo extracted from the SIL-LD device 100 will not become narrower relative to the linewidth of the laser M1.

[0086] The SIL-LD device 100 of this embodiment has a re-locking function to control the device to re-enter the self-injection locked state if the device has lost the self-injection locked state due to temperature or pressure changes inside or outside the device. Specifically, through the re-locking function, the SIL-LD device 100 can continuously monitor the detection value of the light detected by the photodetector 55 on the transmission second mirror 52. The SIL-LD device 100 detects that it has lost the self-injection locked state based on the continuously monitored detection value of the photodetector 55. When the SIL-LD device 100 has lost the self-injection locked state, the SIL-LD device 100 controls the driving current of the semiconductor laser source 4 or the driving voltage of the position adjustment element 21 to make the SIL-LD device 100 return to the self-injection locked state. The re-locking function of the SIL-LD device 100 will be described below.

[0087] (Structure of control unit 150)

[0088] The relocking function of the SIL-LD device 100 is mainly achieved through the control unit of the SIL-LD device 100. Figure 3B This is a block diagram showing the hardware structure of the control unit 150 included in the SIL-LD device 100. (As shown...) Figure 3B As shown, the control unit 150 includes a CPU (Central Processing Unit) 151, a ROM (Read Only Memory) 152, a RAM (Random Access Memory) 153, and an I / F (Interface) 154. These components are interconnected communicatively via the system bus B.

[0089] The control unit 150 realizes its various functions by executing instruction codes stored in a memory by electronic circuits, or by performing various processes through electronic circuits designed for special purposes. Figure 3BIn the example shown, the electronic circuit is CPU151. However, this electronic circuit can also be an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or something similar.

[0090] CPU 151 is a computing device used to control the SIL-LD device 100 as a whole. For example, CPU 151 uses RAM 153 as its working area to execute the processing specified by various control programs stored in ROM 152, and outputs control instructions for controlling various actions of SIL-LD device 100.

[0091] I / F154 is an interface used to connect the control unit 150 to external devices or external apparatuses other than the control unit 150 for communication. External devices may include a position adjustment element driver 161 for driving the position adjustment element 21, a semiconductor laser driver 162 for driving the semiconductor laser source 4, a temperature adjustment element driver 163 for driving the temperature adjustment element 3, and a voltmeter 164 that receives light signals from the photodetector 55 and outputs them as digital voltage signals. External devices may include PCs (Personal Computers) other than the control unit 150.

[0092] Figure 3C This is a block diagram showing the functional structure of the control unit 150 included in the SIL-LD device 100. (For example...) Figure 3C As shown, the SIL-LD device 100 includes a detection value acquisition unit 171, an intensity determination unit 172, a FAST control unit 173, a stabilization time determination unit 174, a FULL control unit 175, a temperature control unit 176, and an output unit 177.

[0093] The functions of the detection value acquisition unit 171 and the output unit 177 are implemented by the I / F 154 or by the CPU 151 executing the processing specified by various control programs stored in the ROM 152. The functions of the intensity determination unit 172, the FAST control unit 173, the stabilization time determination unit 174, the FULL control unit 175, and the temperature control unit 176 are implemented by the CPU 151 executing the processing specified by various control programs stored in the ROM 152. Furthermore, some of the functions of the control unit 150 can be implemented by external devices other than the control unit 150, or by decentralized processing of the control unit 150 and external devices.

[0094] The detection value acquisition unit 171 receives a digital voltage signal output by the voltmeter 164 by controlling communication with the voltmeter 164. The detection value acquisition unit 171 acquires this digital voltage signal and uses it as the detection value of the photodetector 55.

[0095] The intensity determination unit 172 determines whether the detection value of the photodetector 55 obtained by the detection value acquisition unit 171 is below a predetermined intensity threshold. If the intensity determination unit 172 determines that the detection value of the photodetector 55 is below the intensity threshold, the SIL-LD device 100 is detected to have disengaged from the self-injection lock state.

[0096] The FAST control unit 173 controls the drive current of the semiconductor laser source 4 when the SIL-LD device 100 is out of the self-injection locked state, so as to make the SIL-LD device 100 return to the self-injection locked state. Compared with the FULL control unit 175 described later, the FAST control unit 173 can perform the control of making the SIL-LD device 100 return to the self-injection locked state at a high speed.

[0097] The stabilization time determination unit 174 determines whether the stabilization time is below a predetermined time threshold after the FAST control unit 173 performs control. Here, the stabilization time refers to the duration during which the detection value of the photodetector 55, acquired by the detection value acquisition unit 171, is above the intensity threshold. The stabilization time determination unit 174, for example, uses the clock of the CPU 151 to measure the stabilization time and compares the measured stabilization time with the time threshold to determine whether the stabilization time is below the time threshold. If the stabilization time determination unit 174 determines that the stabilization time is below the time threshold, the SIL-LD device 100 detects that its self-injection lock state is unstable. An unstable self-injection lock state of the SIL-LD device 100 means that the SIL-LD device 100 is in a state where it is easy to break out of the self-injection lock state.

[0098] The FULL control unit 175 controls the driving current of the semiconductor laser source 4 and the driving voltage of the position adjustment element 21 when the self-injection locked state of the SIL-LD device 100 is unstable, so as to make the SIL-LD device 100 reach a stable self-injection locked state. Compared with the FAST control unit 173, the FULL control unit 175 can more accurately execute the control to make the SIL-LD device 100 reach the self-injection locked state.

[0099] The temperature control unit 176 controls the operation of the temperature adjustment element 3 to adjust the temperature of the first base plate 1. The SIL-LD device 100 can maintain a constant temperature of the first base plate 1 through the temperature control unit 176.

[0100] The output unit 177 outputs various control signals by controlling the communication between the position adjustment element driver 161, the semiconductor laser driver 162, and the temperature adjustment element driver 163. For example, the output unit 177 outputs the drive current of the semiconductor laser source 4 provided by the FAST control unit 173 and the FULL control unit 175 to the semiconductor laser source 4. Additionally, the output unit 177 outputs the drive voltage of the position adjustment element 21 provided by the FULL control unit 175 to the position adjustment element 21. Furthermore, the output unit 177 outputs the control signal of the drive voltage of the temperature adjustment element 3 provided by the temperature control unit 176 to the temperature adjustment element 3.

[0101] (Processing of Control Unit 150)

[0102] Reference Figure 3D Let me explain the processing of the control unit 150.

[0103] Figure 3D This is a flowchart illustrating an example of the processing performed by the control unit 150. For example, the control unit 150 begins processing when the SIL-LD device 100 becomes a self-injection locked state as a start condition. Figure 3D The processing in the middle.

[0104] First, in step S11, the control unit 150 obtains the detection value of the photodetector 55 processed by the voltmeter 164 through the detection value acquisition unit 171.

[0105] Next, in step S12, the control unit 150 determines, through the intensity determination unit 172, whether the detection value of the photodetector 55 is below a predetermined intensity threshold.

[0106] In step S12, if it is determined that the detection value of the photodetector 55 is not below the predetermined intensity threshold (No in step S12), the control unit 150 determines that the SIL-LD device 100 is in a stable self-injection lock state and moves to the processing of step S16.

[0107] In contrast, in step S12, if it is determined that the detection value of the photodetector 55 is below a predetermined intensity threshold (yes in step S12), the control unit 150 detects that the SIL-LD device 100 has left the self-injection locked state. In step S13, the control unit 150 controls the driving current of the semiconductor laser source 4 through the FAST controller 173 to make the SIL-LD device 100 return to the self-injection locked state.

[0108] Then, in step S14, the control unit 150 determines whether the stabilization time is below a predetermined time threshold by the stabilization time determination unit 174.

[0109] In step S14, if it is determined that the stabilization time is not below the predetermined time threshold (step S14 is no), the control unit 150 determines that the SIL-LD device 100 is in a stable self-injection lock state and moves to the processing of step S16.

[0110] In contrast, in step S14, if it is determined that the stabilization time is below a predetermined time threshold (step S14 is yes), the control unit 150 can detect that the self-injection lock state of the SIL-LD device 100 is not yet stable. In step S15, the control unit 150, through the FULL control unit 175, controls the driving current of the semiconductor laser source 4 and the driving voltage of the position adjustment element 21 to bring the SIL-LD device 100 back into the self-injection lock state. In step S15, the driving voltage of the position adjustment element 21 can be fixed, and the driving current of the semiconductor laser source 4 can be scanned.

[0111] The FULL controller 175 continuously adjusts the drive current of the semiconductor laser source 4 and the drive voltage of the position adjustment element 21 until the SIL-LD device 100 reaches a stable self-injection locked state. After the control unit 150 achieves a stable self-injection locked state for the SIL-LD device 100 under the control of the FULL controller 175, it moves to step S16.

[0112] Then, in step S16, the control unit 150 determines whether to end the process. For example, the control unit 150 determines to end the process if it detects that the power supply to the SIL-LD device 100 has been cut off. Furthermore, the end condition for the control unit 150's process is not limited to the power supply being cut off to the SIL-LD device 100. For example, the end condition may also be that the operation unit of the SIL-LD device 100 receives an operation input instructing the control unit 150 to end the process, a predetermined time has elapsed, or the control unit 150 has performed the process a predetermined number of times.

[0113] In step S16, if the process is determined to end (step S16 is yes), the control unit 150 ends the process. Conversely, if the process is determined not to end (step S16 is no) in step S16, the control unit 150 moves to the process in step S11. The control unit 150 repeatedly performs step S11 and its subsequent processes until the process is determined to end in step S16.

[0114] As described above, the control unit 150 is capable of performing processing to implement the relocking function.

[0115] [Second Implementation]

[0116] Reference Figure 4 and Figure 5The SIL-LD device of the second embodiment will be described below. Furthermore, the same names and symbols as in the previously described embodiments denote the same or similar components or structures, and detailed descriptions are omitted where appropriate. This will also be the case in the descriptions of the embodiments and variations shown below.

[0117] Figure 4 This is a schematic top view showing an example of the SIL-LD device 100a according to the second embodiment. Figure 5 yes Figure 4 A schematic cross-sectional view of the VV line. And, in Figure 4 and Figure 5 In the diagram, a portion of each of the lasers M7 to M10 inside the SIL-LD device 100a is indicated by an arrow. Additionally, in... Figure 4 and Figure 5 In the SIL-LD device 100a, the optical path P through which lasers M7 to M10 pass is represented by a dashed line.

[0118] In this embodiment, the semiconductor laser source 4 includes a DFB-LD element as a semiconductor laser element 401. The reference resonator 5 resonates with the laser M7 emitted from the second end face 42 of the semiconductor laser element 401. Figure 5 As shown, an anti-reflective film 410 is formed on both the first end face 41 and the second end face 42 of the semiconductor laser element 401. The laser M8 emitted from the first end face 41 of the semiconductor laser element 401 is used as the output. From another perspective, the SIL-LD device 100a of this embodiment has a structure in which self-injection locking is performed on the side where the second end face 42 of the semiconductor laser element 401 is located, and light extraction is performed on the side where the first end face 41 of the semiconductor laser element 401 is located. The above are the main differences from the first embodiment. The SIL-LD device 100a of this embodiment is less susceptible to environmental changes, reduces the variation of the optical path length Lb and the resonator length Lc, and reduces the output reduction of the laser extracted from the SIL-LD device 100a.

[0119] For example, if an optical element such as a beam splitter is used to branch the laser light in order to extract laser light from a SIL-LD device, power loss occurs when the laser light is branched. For example, in Figure 1 In the SIL-LD device 100 shown, a portion of the light emitted from the reference resonator 5 and passing through the condenser lens 12 before entering the beam splitter 10 will be transmitted through the beam splitter 10 and will not return to the semiconductor laser source 4. As a result, power loss occurs, causing a reduction in the light output of the laser extracted from the SIL-LD device.

[0120] In this embodiment, by performing self-injection locking on the second end face 42 side of the semiconductor laser element 401, the wavelength of the laser Mo extracted from the SIL-LD device 100a is selected while the linewidth of the laser Mo is reduced. Furthermore, the laser M8 emitted from the first end face 41 of the semiconductor laser element 401 is extracted from the SIL-LD device 100a as laser Mo. Therefore, it is unnecessary to employ branching optical elements such as beam splitters to extract laser Mo from the SIL-LD device 100a, thereby improving the light output of the laser Mo extracted from the SIL-LD device 100a.

[0121] exist Figure 4 and Figure 5 In the example shown, the SIL-LD device 100a also includes a second collimating lens 14. The second collimating lens 14 can be any type of lens, such as a spherical lens or an aspherical lens. The second collimating lens 14 can be composed of two or more lenses. The second collimating lens 14 can be made of materials such as glass, quartz, synthetic quartz, sapphire, or transparent ceramic.

[0122] exist Figure 4 and Figure 5 In the example shown, the semiconductor laser element 401 can emit laser M8 from the first end face 41 and the second end face 42 respectively. After the laser M8 emitted from the first end face 41 passes through the first collimating lens 9 and the first opening 71 of the first cover 7, it is extracted as laser Mo from the SIL-LD device 100a through the transmission light isolator 11 and the second opening 81 of the second cover 8.

[0123] On the other hand, the laser M7 emitted from the second end face 42 of the semiconductor laser element 401 is transmitted through the second collimating lens 14 and the condenser lens 12, and then incident on the reference resonator 5. The laser M7 incident on the reference resonator 5 is reflected by the first mirror 51 and the second mirror 52, and resonates back and forth between the first mirror 51 and the second mirror 52. Figure 4 and Figure 5 The arrow representing laser M9 indicates the laser traveling back and forth between the first mirror 51 and the second mirror 52. A portion of laser M9, while traveling back and forth between the first mirror 51 and the second mirror 52, is emitted from the reference resonator 5 towards the location of the second collimating lens 14. Laser M10 emitted from the reference resonator 5 is transmitted through the condenser lens 12 and the second collimating lens 14, respectively. Laser M10, having been transmitted through the condenser lens 12 and the second collimating lens 14, is incident on the semiconductor laser element 401 and fed back to the optical frequency of laser M8.

[0124] exist Figure 4In the example shown, the optical path length Lb between the semiconductor laser source 4 and the reference resonator 5 is the distance between them. Specifically, it is the distance between the second end face 42 of the semiconductor laser element 401 and the first face 511 of the first mirror 51. The optical path length Lb, as in the first embodiment, represents the length of the optical feedback path in self-injection locking. The resonator length Lc is the same as in the first embodiment.

[0125] In this example, the semiconductor laser element 401 is illustrated as extending along the X direction, but it is not limited to this. The optical path can be adjusted by appropriately changing the emission direction of the laser from the semiconductor laser element 401, or by appropriately arranging a reflecting mirror inside or outside the package of the semiconductor laser source 4.

[0126] [Third Implementation]

[0127] Reference Figure 6 and Figure 7 The SIL-LD device of the third embodiment will be described.

[0128] (Example 1)

[0129] Figure 6 This is a schematic top view showing a first example of the SIL-LD device 100b according to the third embodiment. Figure 7 yes Figure 6 A schematic cross-sectional view of line VII-VII in the diagram. Here, in Figure 6 and Figure 7 In the diagram, a portion of each of the lasers M7 to M12 inside the SIL-LD device 100b is indicated by an arrow. Furthermore, in... Figure 6 and Figure 7 In the SIL-LD device 100b, the optical path P through which lasers M7 to M12 pass is represented by a dashed line.

[0130] In this embodiment, an optical amplifier 18 is also included, located between the optical isolator 11 and the second cover 8, to receive the laser M8 that has passed through the optical isolator 11. This is the main difference from the embodiment described above. In this embodiment, by passing the self-injected locked laser M8 through the optical amplifier 18, the wavelength can be selectively controlled, and the power of the thin-linewidth laser M8 can be amplified.

[0131] like Figure 6 and Figure 7The SIL-LD device 100b shown in the first example, like the second embodiment, has a structure that performs self-injection locking on the side where the second end face 42 of the semiconductor laser source 4 is located, and performs light extraction on the side where the first end face 41 of the semiconductor laser source 4 is located. Furthermore, like the first embodiment, the SIL-LD device 100b may also have a structure that performs self-injection locking and light extraction on the side where the first end face 41 of the semiconductor laser source 4 is located, respectively.

[0132] exist Figure 6 and Figure 7 In the first example shown, the SIL-LD device 100b includes a first reflecting mirror 15 and a second reflecting mirror 16 for reflecting the laser M8 that has passed through the optical isolator 11, and a third collimating lens 17 for transmitting the laser L8 reflected by the second reflecting mirror 16. Additionally, the SIL-LD device 100b includes a fourth collimating lens 19 for transmitting the laser M11 that has passed through the optical amplifier 18, and a third base plate 20 for mounting the third collimating lens 17, the optical amplifier 18, and the fourth collimating lens 19.

[0133] (First reflector 15 and second reflector 16)

[0134] The first reflector 15 and the second reflector 16 are aligned so that the laser M8 is properly incident on the third collimating lens 17. The first reflector 15 and the second reflector 16 can be constructed from materials such as glass, quartz, synthetic quartz, sapphire, or transparent ceramic. The positions of the first reflector 15 and the second reflector 16 can be appropriately selected according to the specifications of the SIL-LD device 100b. Here, the SIL-LD device 100b does not necessarily include mirrors such as the first reflector 15 and the second reflector 16; it may include one or more mirrors.

[0135] (Third collimating lens 17 and fourth collimating lens 19)

[0136] The third collimating lens 17 and the fourth collimating lens 19 can each use various types of lenses, such as spherical lenses and aspherical lenses. The third collimating lens 17 and the fourth collimating lens 19 can each be a structure combining two or more lenses. The third collimating lens 17 and the fourth collimating lens 19 can each be constructed from materials such as glass, quartz, synthetic quartz, sapphire, or transparent ceramic.

[0137] (Optical Amplifier 18)

[0138] The optical amplifier 18 is located between the optical isolator 11 and the second cover 8, and is positioned so that the laser M8 passing through the optical isolator 11 is incident upon it. Alternatively, the optical amplifier 18 can be positioned outside the first cover 7 and inside the second cover 8, between the optical isolator 11 and the second cover 8, with the optical path P passing through the optical amplifier 18. The optical amplifier 18 can be a semiconductor optical amplifier (SOA). Examples of semiconductor optical amplifiers include nitride semiconductors, arsenide semiconductors, and phosphide semiconductors. However, the optical amplifier 18 is not limited to semiconductor optical amplifiers; rare-earth-doped optical fibers can also be used. Furthermore, when amplifying visible light such as blue light, a semiconductor optical amplifier is preferred as the optical amplifier 18.

[0139] In this embodiment, an optical isolator 11 is disposed between the semiconductor laser element 401 and the optical amplifier 18. The optical isolator 11 can reduce the amount of light amplified by the optical amplifier 18 that returns to the semiconductor laser element 401, thereby improving the stability of the single-mode performance of the SIL-LD device 100.

[0140] (Third base plate 20)

[0141] As long as at least a third collimating lens 17, an optical amplifier 18, and a fourth collimating lens 19 can be mounted, the shape and size of the third base plate 20 can be appropriately selected. The material of the third base plate 20 preferably includes at least one material selected from the group consisting of aluminum, copper, graphite, diamond, aluminum nitride, and super Invar alloy. Since aluminum, copper, graphite, diamond, and aluminum nitride have high thermal conductivity, they are advantageous in terms of heat dissipation generated by the optical amplifier 18. Furthermore, since super Invar alloy is less prone to thermal expansion, it can reduce the positional deviation of the optical amplifier 18, thereby reducing the deviation of the third collimating lens 17 from the focal point position.

[0142] (Second example)

[0143] Figure 8 This is a schematic top view showing a second example of the SIL-LD device 100b according to the third embodiment.

[0144] Figure 8 The second example of the SIL-LD device 100b shown is the same as the first embodiment, but the difference between the second example and the first example of the SIL-LD device 100b is that it has a structure in which self-injection locking and light extraction are performed on the side where the first end face 41 of the semiconductor laser source 4 is located.

[0145] exist Figure 8 In the second example shown, with Figure 6 and Figure 7Similarly, in the first example shown, the SIL-LD device 100b directs the laser M8, which has passed through the optical isolator 11, through the first reflector 15, the second reflector 16, and the third collimating lens 17 to the optical amplifier 18. By directing the self-injection-locked laser M8 through the optical amplifier 18, the wavelength can be selected while the power of the narrow-linewidth laser M8 is amplified. The SIL-LD device 100b is able to extract the amplified laser Mo.

[0146] [Variation Example 1]

[0147] Next, a variation 1 of the SIL-LD device according to the embodiment will be described. Figure 9 This is a schematic top view of the SIL-LD device 100c of Modified Example 1.

[0148] The SIL-LD device 100c of Modified Example 1 includes a first substrate 1c having a recess 22, a second base plate 2 corresponding to the second substrate, a temperature adjustment element 3 disposed between the first substrate 1c and the second base plate 2, and a semiconductor laser source 4 disposed in the recess 22 of the first substrate 1c. Furthermore, the SIL-LD device 100c also includes a reference resonator 5 disposed in the recess 22 of the first substrate 1c and located in the optical path of the laser M1 emitted from the semiconductor laser source 4. Moreover, the SIL-LD device 100c also includes a first cover 7 covering the semiconductor laser source 4 and the reference resonator 5 and in contact with the first substrate 1c, and a second cover 8 covering the first cover 7 and in contact with the second base plate 2.

[0149] exist Figure 9 In the example shown, the first substrate 1c includes a bottom surface 221, a first side surface 222, a second side surface 223, and a top surface 224. The recess 22 is at least the portion defined by the bottom surface 221, the first side surface 222, and the second side surface 223. The first substrate 1c is preferably made of a material with low thermal expansion, such as a super Invar alloy. The first substrate 1c may be made of the same material as the first base plate 1 described in the SIL-LD device 100 of Embodiment 1.

[0150] exist Figure 9 In the example shown, the second substrate is illustrated as a second base plate 2, but is not limited thereto. The second substrate may include a recess. The first substrate 1c and the optical isolator 11 may also be disposed within the recess of the second substrate.

[0151] A semiconductor laser source 4 and a reference resonator 5 are disposed on the bottom surface 221 of the first substrate 1c. The semiconductor laser source 4 and the reference resonator 5 are sealed by the first substrate 1c and a first cover 7. This facilitates the stabilization of the environment within the space sealed by the first cover 7, extending the time during which the laser M1 can maintain its frequency after resonating with the reference resonator 5. Figure 9In the example shown, a portion of the upper surface 224 of the first substrate 1c is formed into a recessed shape, and the O-ring 73 is disposed in the recessed area of ​​this portion of the upper surface 224. This allows for easy sealing. The first cover 7 is a flat plate, and its lower surface 72 is disposed opposite to the upper surface 224 of the first substrate 1c via the O-ring 73. This also allows for easy sealing. The sealed space can be filled with dry air, nitrogen, or an inert gas such as a rare gas. Alternatively, a vacuum can be used. This reduces the effect of external sound and vibration. A gasket can also be used instead of the O-ring 73.

[0152] The first cover 7 is fixed to the first base 1c by screws 74. Therefore, the first cover 7 is easily disassembled, facilitating the inspection and adjustment of the semiconductor laser source 4 or the reference resonator 5. Figure 9 As shown, when the screw 74 fixes the first cover 7 at a position closer to the recess 22 than the O-ring 73, it is preferable to also provide an O-ring 73 between the screw 74 and the first cover 7 to improve airtightness.

[0153] In the SIL-LD device 100c of Modified Example 1, the same effects as those of the SIL-LD device 100 of the first embodiment can be obtained. Furthermore, the first substrate 1c and the flat first cover 7 in the SIL-LD device 100c are not limited to the SIL-LD device 100 of the first embodiment; the SIL-LD device a of the second embodiment and the SIL-LD device b of the third embodiment can also be used.

[0154] <Experimental Results>

[0155] In the SIL-LD device 100c, where the semiconductor laser source 4 and the reference resonator 5 are hermetically sealed by the first cover 7 and the first substrate 1c, the laser and the reference resonator 5 resonate and output a fine-linewidth laser for approximately 80 hours. In the SIL-LD device 100 where the first cover 7 is not hermetically sealed, the laser and the reference resonator 5 resonate and output a fine-linewidth laser for only a few hours. Therefore, it can be determined that a more stable drive can be achieved through hermetical sealing.

[0156] [Variation Example 2]

[0157] Next, a variation 2 of the SIL-LD device according to the embodiment will be described. Figure 10 This is a schematic top view of the SIL-LD device 100d in Modified Example 2.

[0158] The difference between the SIL-LD device 100d in Modified Example 2 and the SIL-LD device 100c in Modified Example 1 is that the screw 74 is fixed at a position further away from the recess 22 than the O-ring 73. Therefore, even without the O-ring 73 between the screw 74 and the first cover 7, it is easier to achieve an airtight seal. Other aspects are the same as those in the SIL-LD device 100c of Modified Example 1.

[0159] [Fourth Implementation]

[0160] Reference Figure 11 This describes the molecular information output device 200 of the fourth embodiment. Figure 11 This is a schematic top view showing a portion of the molecular information output device 200 according to the fourth embodiment.

[0161] In this embodiment, in the molecular information output device 200, a molecule S, which is the object of detection, is sealed between the first mirror 51 and the second mirror 52 of the reference resonator 5 constituting the SIL-LD devices 100, 100a, and 100b described in the first to third embodiments. Other structures are common to the SIL-LD devices 100, 100a, or 100b, and are omitted from the drawings for simplicity. In the molecular information output device 200, a photodetector 55 that receives light transmitted through the reference resonator 5 is used for confirmation of the self-injection locking action, and also outputs information about the molecule S.

[0162] The molecular information output device 200 can acquire and output relevant information about the molecule S with ultra-high sensitivity by interacting with the electromagnetic properties of the molecule S within the reference resonator 5 during the self-injection locking operation, using a high-intensity, narrow-linewidth laser. The first cover 7 also stabilizes the state of the molecule S, improving measurement accuracy. The molecule S is, for example, a gas molecule. However, the molecule S can also be a molecule other than a gas, such as a liquid. Information about the molecule S, such as its concentration, absorbance, temperature, composition, and isotope ratio, can be obtained, for example, by the electrical signal output from the photodetector 55 that receives the laser Ma1 extracted from the reference resonator 5. From the viewpoint of improving the accuracy of the relevant information 210 about the molecule S, the reference resonator 5 preferably has a Q value that is as high as possible.

[0163] The photodetector 55 receives the light signal from the laser Ma1 extracted from the reference resonator 5 and outputs it as relevant information 210 of the molecule S. The photodetector 55 can use a photodiode or the like.

[0164] The preferred embodiments have been described in detail above, but are not limited to the embodiments described above. Various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0165] The ordinal numbers, quantities, and other numerical values ​​used in the description of the embodiments are all for illustrative purposes only, and the invention is not limited to the illustrative numbers. Furthermore, the connection relationships between structural elements are for illustrative purposes only, and the connection relationships used to achieve the functions of the invention are not limited to these.

[0166] The SIL-LD device disclosed herein is capable of extracting laser light with a narrow linewidth, and is therefore preferably used as a light source for information output devices, analysis devices, or various optical devices. Furthermore, as one preferred application example, the use of wavelength conversion via a nonlinear optical crystal can be cited.

[0167] Various embodiments of the present invention include the following structures.

[0168] <Item 1> A self-injection locking laser device includes: a first base plate; a second base plate; a temperature adjustment element disposed between the first base plate and the second base plate; a semiconductor laser source disposed on the first base plate; a reference resonator disposed on the first base plate, located in the optical path of the laser emitted from the semiconductor laser source, and including at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser source; a first cover covering the semiconductor laser source and the reference resonator, and in contact with the first base plate; and a second cover covering the first cover and in contact with the second base plate.

[0169] <Item 2> According to the self-injection locking laser device described in <Item 1> above, the temperature adjustment element includes a Peltier element.

[0170] <Item 3> According to the self-injection locking laser device described in <Item 1> or <Item 2> above, the temperature sensor is embedded in the first base plate.

[0171] <Item 4> According to any one of <Item 1> to <Item 3> above, the materials of the first base plate and the second base plate include at least one selected from the group consisting of aluminum, copper, graphite, diamond, aluminum nitride, super Invar alloy and low thermal expansion glass.

[0172] <Item 5> According to any one of <Item 1> to <Item 4> above, the material of the first cover includes aluminum or copper.

[0173] <Item 6> According to any one of <Item 1> to <Item 5> above, the self-injection locking laser device, the semiconductor laser source includes a distributed feedback laser element.

[0174] <Item 7> According to the self-injection locking laser device described in <Item 6> above, the distributed feedback laser element includes a first end face and a second end face opposite to the first end face, the reference resonator resonates with the laser emitted from the second end face, and the laser emitted from the first end face is used as the output.

[0175] <Item 8> According to any one of <Item 1> to <Item 7> above, the self-injection locking laser device, the semiconductor laser source and the reference resonator are sealed by the first base plate and the first cover.

[0176] <Item 9> A self-injection locking laser device includes: a first substrate including a recess; a second substrate; a temperature adjustment element disposed between the first substrate and the second substrate; a semiconductor laser source disposed in the recess of the first substrate; a reference resonator disposed in the recess of the first substrate, located in the optical path of a laser emitted from the semiconductor laser source, and including at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser source; a first cover covering the semiconductor laser source and the reference resonator, and in contact with the first substrate; and a second cover covering the first cover and in contact with the second substrate.

[0177] <Item 10> According to the self-injection locking laser device described in <Item 9> above, the semiconductor laser source and the reference resonator are sealed by the first substrate and the first cover.

[0178] <Item 11> The self-injection locking laser device according to any one of <Item 1> to <Item 10> above further includes: an optical isolator located between the first cover and the second cover, and located on the optical path.

[0179] <Item 12> The self-injection locking laser device according to <Item 11> above further includes: an optical amplifier located between the optical isolator and the second cover, wherein the laser light passing through the optical isolator is incident on the optical amplifier.

[0180] <13> A molecular information output device, in any one of the above-described self-injection locking laser devices (items 1 to 12), further comprises a molecule as the object of detection within the reference resonator.

[0181] This application claims priority based on Japanese Patent Application No. 2023-214224, filed with the Japan Patent Office on December 19, 2023, and incorporates the entire contents of that Japanese Patent Application.

[0182] Symbol Explanation

[0183] 1. First base plate

[0184] 1c First matrix

[0185] 2 Second base plate

[0186] 3 Temperature adjustment element

[0187] 4. Semiconductor laser source

[0188] 41 First end face

[0189] 42 Second end face

[0190] 401 Semiconductor Laser Components

[0191] 402 package

[0192] 410 Anti-reflective film

[0193] 420 High Reflectivity Film

[0194] 5. Reference Resonator

[0195] 51 First Shot

[0196] 511 First Page

[0197] 512 Second page

[0198] 513 Third page

[0199] 514 Fourth page

[0200] 52 Second Shot

[0201] 55 Photodetectors

[0202] 7 First Cover

[0203] 71 First Opening

[0204] 710 Light-transmitting components

[0205] 73 O rings

[0206] 74 screws

[0207] 8 Second cover

[0208] 81 Second opening

[0209] 810 Light-transmitting components

[0210] 9 First collimating lens

[0211] 10 beam splitters

[0212] 11 Optical Isolators

[0213] 12 Condensing Lenses

[0214] 13 Temperature Sensor

[0215] 14 Second collimating lens

[0216] 15 First reflecting mirror

[0217] 16 Second reflecting mirror

[0218] 17 Third collimating lens

[0219] 18 Optical Amplifier

[0220] 19 Fourth collimating lens

[0221] 20 Third base plate

[0222] 21 Position Adjustment Element

[0223] 100, 100a, 100b, 100c, 100d Self-injection locking laser devices

[0224] 150 Control Department

[0225] 151 CPU

[0226] 152 ROM

[0227] 153 RAM

[0228] 154 I / F

[0229] 161 Position Adjustment Element Driver

[0230] 162 Semiconductor Laser Driver

[0231] 163 Temperature Adjustment Element Driver

[0232] 164 Voltmeter

[0233] 171 Detection Value Acquisition Department

[0234] 172 Strength Judgment Section

[0235] 173 FAST Control Department

[0236] 174 Stable Time Determination Department

[0237] 175 Full Control Unit

[0238] 176 Temperature Control Department

[0239] 200-molecule information output device

[0240] 210 Molecular Information

[0241] B System Bus

[0242] C Central axis

[0243] Lc reference resonator resonator length

[0244] Lb optical path length

[0245] Lb1 and Lb2 lengths

[0246] Mo, M1~M11, Ma1 lasers

[0247] P optical path

[0248] S molecule

Claims

1. A self-injection locking laser device, comprising: First base plate; Second base plate; A temperature adjustment element is disposed between the first base plate and the second base plate; A semiconductor laser source is disposed on the first base plate; A reference resonator, disposed on the first base plate, is located in the optical path of the laser emitted from the semiconductor laser source, and includes at least a first mirror and a second mirror, for providing optical feedback to the semiconductor laser source; A first cover covers the semiconductor laser source and the reference resonator, and is in contact with the first base plate; and The second cover covers the first cover and contacts the second base plate.

2. The self-injection locking laser device according to claim 1, wherein, The temperature adjustment element includes a Peltier element.

3. The self-injection locking laser device according to claim 1 or 2, wherein, The temperature sensor is embedded in the first base plate.

4. The self-injection locking laser device according to any one of claims 1 to 3, wherein, The materials of the first base plate and the second base plate include at least one selected from the group consisting of aluminum, copper, graphite, diamond, aluminum nitride, super Invar alloy and low thermal expansion glass.

5. The self-injection locking laser device according to any one of claims 1 to 4, wherein, The material of the first cover includes aluminum or copper.

6. The self-injection locking laser device according to any one of claims 1 to 5, wherein, The semiconductor laser source includes a distributed feedback laser element.

7. The self-injection locking laser device according to claim 6, wherein, The distributed feedback laser element includes a first end face and a second end face opposite to the first end face. The reference resonator resonates with the laser emitted from the second end face. The laser emitted from the first end face is used as the output.

8. The self-injection locking laser device according to any one of claims 1 to 7, wherein, The semiconductor laser source and the reference resonator are sealed by the first base plate and the first cover.

9. A self-injection locking laser device, comprising: The first substrate including the recess; Second matrix; A temperature adjustment element is disposed between the first substrate and the second substrate; A semiconductor laser source is disposed in the recess of the first substrate; A reference resonator, disposed in the recess of the first substrate, is located in the optical path of the laser emitted from the semiconductor laser source, and includes at least a first mirror and a second mirror for providing optical feedback to the semiconductor laser source; A first cover covers the semiconductor laser source and the reference resonator, and is in contact with the first substrate; and The second cover covers the first cover and is in contact with the second substrate.

10. The self-injection locking laser device according to claim 9, wherein, The semiconductor laser source and the reference resonator are sealed by the first substrate and the first cover.

11. The self-injection locking laser device according to any one of claims 1 to 10, further comprising: An optical isolator is located between the first cover and the second cover, and is situated on the optical path.

12. The self-injection locking laser device according to claim 11, further comprising: An optical amplifier is located between the optical isolator and the second cover, and the laser light passing through the optical isolator is incident on the optical amplifier.

13. A molecular information output device, comprising: According to any one of claims 1 to 12, a molecule as the detection target is sealed between the first mirror and the second mirror; and A photodetector receives laser light extracted from the reference resonator and outputs information related to the molecule.

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