A wavelength-locked semiconductor laser module operating at low temperature

Abstract

A low-temperature working wavelength-locked pump laser module comprises a tube shell, a low-thermal-expansion coefficient heat sink, a semiconductor laser chip, a collimating optical assembly, a dual-wavelength selective reflection element, a sealed optical window and a sealed cover plate; after the light emitted by the semiconductor laser chip is collimated, the dual-wavelength selective reflection element partially feeds back the output laser to form an external cavity, thereby realizing wavelength locking and spectral narrowing of the semiconductor laser chip; the dual-wavelength selective reflection element has a low-temperature working wavelength and a normal-temperature debugging wavelength, and can be fixed after debugging at normal temperature; when working in a low-temperature environment, any element does not need to be adjusted, and the required wavelength locking and spectral narrowing are automatically realized; the module adopts a sealed structure to improve reliability; the application solves the problems of wavelength locking failure and complex debugging of traditional lasers in a low-temperature environment, has the advantages of simple normal-temperature debugging, stable low-temperature working, precise wavelength locking, high reliability and the like, and is suitable for a fiber laser pump source in an extreme low-temperature environment.

Description

Technical Field

[0001] This invention relates to laser technology, and more particularly to a wavelength-locked pump laser module that can operate in low-temperature environments, suitable for high-power fiber lasers, high-energy solid-state lasers, or industrial processing in extreme environments. Background Technology

[0002] Wavelength-locked semiconductor lasers are key components of high-power fiber lasers. Wavelength locking can significantly reduce the temperature control requirements of fiber laser systems and improve the optical-optical efficiency of fiber lasers. Fiber lasers have broad application prospects in industrial processing, laser communication, and high-energy laser special fields. While operating at low temperatures (below 5°C or even lower) can improve the electro-optical efficiency of semiconductor laser chips in special applications, wavelength locking of the pump source fails at extreme operating temperatures, thus reducing the optical-optical efficiency of high-power fiber lasers.

[0003] Traditionally, wavelength-locked semiconductor lasers operate near room temperature (25°C). Since the wavelength temperature coefficient of the semiconductor laser chip (typically 0.3 nm / °C) is much larger than that of the external cavity wavelength-locked optical element (typically less than 0.01 nm / °C), when the operating temperature drops below 5°C or -50°C, the wavelength difference between the semiconductor laser chip and the external cavity wavelength-locked optical element becomes too large, making it impossible to achieve wavelength locking and spectral narrowing. This significantly reduces the optical efficiency of the pump at low temperatures.

[0004] Current literature reports that operating semiconductor laser chips or arrays at low temperatures can significantly improve electro-optic efficiency. The literature "A Wavelength-Stable Semiconductor Laser Source with Tunable Full Power Range for High and Low Temperatures" reports a light source operating at -55°C. This method uses a semiconductor cooler to control the semiconductor laser chip at room temperature to stabilize the wavelength. However, because semiconductor coolers generally have low efficiency and do not achieve wavelength locking and spectral narrowing, the overall efficiency of the light source is relatively low when applied to fiber laser pumping. Patent CN119009666B discloses a wavelength-locked semiconductor laser that achieves tunable diffraction efficiency through polarization control. Adjusting the diffraction efficiency addresses the issue of the locking range varying with temperature and current. Increasing the diffraction efficiency can solve the wavelength locking range problem to some extent, but excessively high diffraction efficiency can affect the electro-optic efficiency of the laser and even damage the laser chip. Patent CN 118920277A discloses a wavelength locking and linewidth compression system that achieves wavelength locking for multiple light sources through fiber combiners and diffractive optical elements. Patent CN113131336B describes a method to achieve wavelength locking of a laser by changing the current and temperature of the semiconductor laser chip, avoiding cavity surface catastrophe damage during debugging and improving the stability of the wavelength-locked state. Patent CN120016261A discloses a low-temperature operating fiber laser. By designing the relative position of the wavelength of the semiconductor laser at room temperature and the absorption peak of the gain fiber, when the temperature approaches or falls below zero, the rapid wavelength drift of the non-wavelength-locked semiconductor laser is matched with the absorption peak of the gain fiber. At this time, the spectrum of the non-wavelength-locked semiconductor laser is wider (2nm~3nm), and the optical efficiency of the fiber laser is affected.

[0005] In summary, although there are currently various methods for wavelength locking of semiconductor lasers, wavelength locking and spectral narrowing cannot be achieved directly at low temperatures (below 5°C). If conventional wavelength locking adjustment methods are used to achieve wavelength locking at low temperatures, adjustments and fixation need to be performed at near-low temperature conditions. At this time, the adhesive curing time is long or even fails to cure. At the same time, maintaining low temperature requires complex drying or vacuum systems to ensure that there is no condensation on the laser chip cavity surface, which brings complexity to process adjustment and high cost. Summary of the Invention

[0006] This invention aims to overcome the technical shortcomings of existing wavelength-locked semiconductor lasers, such as locking failure at low temperatures, reliance on active temperature control by semiconductor coolers, and the need for complex on-site debugging at low temperatures (e.g., difficulties in adhesive curing and high risk of condensation). It provides a wavelength-locked semiconductor laser module that operates at low temperatures. This module employs a dual-wavelength selective reflection element with two preset reflection wavelengths (a room-temperature adjustment wavelength and a low-temperature operating wavelength). Utilizing the significant difference in wavelength temperature coefficients between the semiconductor laser chip and the reflection element, the interval between the two reflection wavelengths is quantitatively designed using a formula. This ensures that the blue shift of the chip's free-running wavelength precisely compensates for this interval during the temperature drop from room temperature to low temperature, achieving an external cavity feedback operating mode of "one-time assembly and adjustment at room temperature, passive locking at low temperature."

[0007] The technical solution of the present invention is as follows: A low-temperature operating wavelength-locked semiconductor laser module includes: The casing serves as the basic housing for the overall encapsulation.

[0008] A heat sink with a low coefficient of thermal expansion is fixed to the inner bottom surface of the tube shell to provide stable mechanical support and an efficient heat conduction path.

[0009] A semiconductor laser chip is fixed to the upper surface of the low thermal expansion coefficient heat sink and is used to emit a laser beam. This chip is preferably a Fabry-Perot cavity chip, with a high-reflectivity coating on the rear cavity surface and an anti-reflection coating on the emitting surface to enhance the external cavity feedback efficiency.

[0010] The collimating optical component is fixed to the upper surface of the low thermal expansion coefficient heat sink and located in the optical path of the emitted laser beam of the semiconductor laser chip, and is used to collimate the diverging laser beam.

[0011] A dual-wavelength selective reflection element is fixed to the upper surface of the low thermal expansion coefficient heat sink and located behind the output optical path of the collimating optical assembly. It is positioned opposite the semiconductor laser chip along the optical path, together forming an external cavity feedback structure. This element has a first reflection wavelength λ1 and a second reflection wavelength λ2, where λ1 is a preset low-temperature operating wavelength and λ2 is a preset room-temperature adjustment wavelength.

[0012] A sealed optical window is welded to the side wall or end wall of the tube shell and located in the optical path of the output laser after the action of the dual-wavelength selective reflection element, in order to achieve airtightness and allow laser output.

[0013] A sealing cover is sealed to the tube shell, and the low thermal expansion coefficient heat sink, semiconductor laser chip, collimating optical components and dual wavelength selective reflection element are hermetically installed inside the tube shell.

[0014] The wavelength difference Δλ between the two reflected wavelengths of the dual-wavelength selective reflection element satisfies the following formula: Δλ=(T room -T low ) λ T-chip T low T is the preset low-temperature operating temperature. room For room temperature assembly, λ T-chip The temperature coefficient of the center wavelength of the semiconductor laser chip is typically 0.15 nm / ℃ to 0.5 nm / ℃.

[0015] This formula ensures that during the process of cooling from room temperature to low temperature, the blue shift of the free-running wavelength of the semiconductor laser chip exactly matches the interval between λ1 and λ2, thus automatically achieving wavelength locking at low temperatures without any adjustment.

[0016] Preferably, the wavelength temperature coefficient of the semiconductor laser chip is greater than that of the dual-wavelength selective reflection element, so that at the room temperature adjustment temperature T room With the aforementioned low-temperature operating temperature T low When the wavelengths change, the drift of the chip's free-running wavelength is greater than the drift of the reflected wavelength of the reflective element, ensuring that the two can be re-aligned at low temperatures.

[0017] As a further preferred option, the low-temperature operating temperature T low The range is -50℃ to 5℃, and the ambient temperature adjustment temperature T is... room The temperature range is 15℃ to 30℃.

[0018] As an alternative improvement, the module further includes a focusing optical component and an output optical fiber. The focusing optical component is fixed to the upper surface of the low thermal expansion coefficient heat sink or inside the tube housing, and is located between the sealed optical window and the dual-wavelength selective reflection element or inside the sealed optical window; the input end of the output optical fiber is sealed to the tube housing and is located at the focal point of the output optical path of the focusing optical component, so that the output laser after feedback from the dual-wavelength selective reflection element is coupled into the output optical fiber sequentially through the collimating optical component, the dual-wavelength selective reflection element, and the focusing optical component, thereby achieving fiber-coupled output.

[0019] Preferably, the tube shell is filled with a dry gas (such as nitrogen, argon, or air), and is hermetically sealed through the sealed optical window and sealing cover to prevent condensation inside the module in environments below 5°C.

[0020] Preferably, the free operating wavelength of the semiconductor laser chip at room temperature is aligned with the room temperature adjustment wavelength λ2; at low temperature, the free operating wavelength of the semiconductor laser chip is blue-shifted and automatically aligned with the low-temperature operating wavelength λ1.

[0021] As an extension, the semiconductor laser chip can be one or more. When there are multiple chips, they can be spatially combined or polarization combined using lenses and mirrors, and then together with the dual-wavelength selective reflection element to form an external cavity feedback structure; or, multiple chips can each form an external cavity feedback structure with their respective dual-wavelength selective reflection element, and then be combined and output through a beam combining element to achieve higher power output.

[0022] Preferably, after the dual-wavelength selective reflective element is assembled and adjusted at room temperature, it is fixed to the upper surface of the heat sink with a low coefficient of thermal expansion by means of ultraviolet thermosetting adhesive or welding, without the need for secondary fine-tuning in a low-temperature environment.

[0023] In one specific variant, the dual-wavelength selective reflective element is a dual-wavelength selective fiber grating. In this case, the dual-wavelength selective fiber grating serves simultaneously as an external cavity feedback element and an output fiber; the collimating optical component is replaced by a coupling lens group, which is fixed to the upper surface of the low thermal expansion coefficient heat sink and located in the output optical path of the semiconductor laser chip, used to couple the output laser from the chip into the fiber core of the fiber grating; the input end of the dual-wavelength selective fiber grating is connected to the housing, and its output end extends outside the housing.

[0024] The heat sink with a low coefficient of thermal expansion is preferably made of copper-tungsten alloy or aluminum nitride. The semiconductor laser chip is fixed to the upper surface of the heat sink by gold-tin eutectic bonding to ensure good thermal contact and mechanical stability.

[0025] Compared with the prior art, the present invention has the following advantages: 1) By pre-designing two specific intervals of reflection wavelengths on a reflective element and utilizing the difference in wavelength temperature coefficients between the chip and the reflective element, the blue shift of the chip's free-running wavelength automatically compensates for this wavelength interval when the module is cooled from room temperature to a low temperature, achieving external cavity locking without any active temperature control or mechanical adjustment. This mechanism completely solves the fundamental problem of locking failure below 5°C in traditional solutions.

[0026] 2) The entire process is fixed at room temperature, without the need for semiconductor coolers or complex temperature control measures. It utilizes the dual-wavelength characteristics of dual-wavelength selective reflective elements to compensate for the thermal drift of the chip wavelength, achieving a passive working mode of "room temperature adjustment and low temperature automatic locking". The packaging process is simple and low cost.

[0027] 3) Modular design with strong structural stability, adaptable to the pumping requirements of high-power fiber lasers, reducing the temperature control requirements of the entire system in low-temperature operating environments, and improving the overall optical efficiency of the system.

[0028] 4) Low thermal expansion coefficient heat sink is used to reduce optical path drift during temperature changes; hermetic packaging and filling with dry gas effectively prevent low-temperature condensation; all components are fixed by welding or high-stability adhesive, providing strong resistance to vibration and impact. The module can operate stably for a long time within the range of -50℃ to 5℃. Attached Figure Description

[0029] To more clearly illustrate the embodiments or technical solutions of this invention, the drawings used in the description of the embodiments or technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other similar drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a block diagram of the wavelength-locking structure of the low-temperature operating wavelength-locked semiconductor laser module of the present invention. Figure 2 This is a schematic diagram illustrating the block wavelength locking principle of the low-temperature operating wavelength-locked semiconductor laser mode of the present invention. Figure 3 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the structure of Embodiment 3 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments and accompanying drawings, but these should not be construed as limiting the scope of protection of the present invention.

[0032] A wavelength-locked semiconductor laser module operating at low temperature mainly includes a semiconductor laser chip 11, a collimating optical lens group 12, and a dual-wavelength selective reflection element 13.

[0033] The semiconductor laser chip 11 outputs a laser beam, which is collimated by the collimating optical lens group 12, and then forms an external cavity through wavelength feedback via the dual-wavelength selective reflection element 13. When operating at room temperature (25℃), the free spectrum of the semiconductor laser chip 11 and the wavelength λ of the dual-wavelength selective reflection element 13 are... H Basic alignment is achieved at room temperature by adjusting the dual-wavelength selective reflection element 13 to realize wavelength locking and spectral narrowing of the semiconductor laser chip 11, with the locked wavelength being λ. HWhen the module operates at low temperatures (e.g., -25°C), the free-running spectrum of the semiconductor laser chip 11 undergoes a blue shift (approximately 15nm = 50°C × 0.3nm / °C, where 50°C is the temperature difference between the debugging temperature and the low-temperature operating temperature, and the chip's wavelength temperature coefficient is 0.3nm / °C). This blue shift is related to the second wavelength (operating wavelength) λ designed for the dual-wavelength selective reflection element 13. L Essentially the same, since the gratings corresponding to the two designed reflection wavelengths of the dual-wavelength selective reflective element 13 are parallel, wavelength locking and spectral narrowing can be achieved at low temperatures without further adjustment of the dual-wavelength selective reflective element 13. L To provide the wavelength required for low-temperature operation, the wavelength corresponding to the dual-wavelength selective reflective element 13 at room temperature is λ. L +0.01nm / ℃×50℃ (assuming the wavelength temperature coefficient of the dual-wavelength selective reflective element 13 is 0.01nm / ℃). The two feedback wavelengths of the dual-wavelength selective reflective element 13 differ by approximately 15nm (determined by the temperature difference between the low-temperature operating temperature and the room temperature temperature, as well as the wavelength temperature coefficient of the semiconductor laser chip).

[0034] Figure 2 To further explain the wavelength locking principle during low-temperature operation, the first peak wavelength 21-1 of the free-running spectrum 21 of the semiconductor laser chip at room temperature (25℃) is λ1. When the operating temperature drops to a low temperature (-25℃), the peak wavelength 21-2 of the free-running spectrum 21 of the semiconductor laser chip is λ2, and λ1-λ2 is 15nm (wavelength temperature coefficient is 0.3nm / ℃). The wavelengths corresponding to the reflection spectrum 22 of the dual-wavelength selective reflection element are the low-temperature operating wavelength peak 22-1, which is λ1. L +0.01nm / ℃×50℃ and the peak wavelength at room temperature is 22-2 wavelength. H (Wavelength adjustment). The reflected wavelength λ is used when performing wavelength locking and spectral narrowing at room temperature. H Spectral locking is achieved by aligning with the free wavelength λ1 of the semiconductor laser, and λ is considered to be... H To adjust the wavelength. When operating at low temperature, the peak wavelength of the free spectrum of the semiconductor laser blue-shifts to the peak wavelength 21-2, and simultaneously, the reflection spectrum of the dual-wavelength selective reflector also exhibits a blue shift, with the peak wavelength of the reflection spectrum at 22-3 being λ. L Alignment with λ2 of the peak wavelength 21-2 of the low-temperature semiconductor laser chip achieves wavelength locking and spectral narrowing at low temperatures.

[0035] Example 1: Single-chip wavelength locking module based on volume Bragg grating Please refer to Figures 1-3This embodiment provides a wavelength-locked semiconductor laser module that operates at low temperature. It uses a volume Bragg grating as a dual-wavelength selective reflection element and is suitable for application scenarios that require direct spatial light output.

[0036] like Figure 3 As shown, a low-temperature operating wavelength-locked semiconductor laser module includes: a housing 31, a low-expansion-coefficient heat sink 32, an hermetically sealed optical window 33, a dual-wavelength selective volume Bragg grating 34, a collimating optical component 35, a semiconductor laser chip 36, and a sealing cover 37. The low-expansion-coefficient heat sink 32 is welded to the bottom surface inside the housing 31. The semiconductor laser chip 36, the collimating optical component 35, and the dual-wavelength selective volume Bragg grating 34 are sequentially fixed to the upper surface of the low-expansion-coefficient heat sink 32. The semiconductor laser chip 36 is fixedly connected to the low-expansion-coefficient heat sink 32 by metal welding. After the collimating optical component 35 and the dual-wavelength selective volume Bragg grating 34 are adjusted to achieve room-temperature wavelength locking, they are fixed to the upper surface of the low-expansion-coefficient heat sink 32 with adhesive or welding. The hermetically sealed optical window 33 is connected to the housing 31 by metal welding or adhesive bonding to achieve hermetical tightness. After the optical path is assembled, dry gas is filled into the tube shell 31, and the sealing cover 37 is connected to the shell 31 by parallel sealing welding or adhesive bonding to achieve the airtightness of the cover.

[0037] At room temperature (25℃), the laser output from the semiconductor laser chip 36 is collimated by the collimating optical component 35. The center wavelength of the free-running spectrum at room temperature is approximately 991nm. The laser is then diffracted by the dual-wavelength selective volume Bragg grating 34 at wavelength λ. H =991nm (tuning wavelength, the other diffraction wavelength of the volume Bragg grating is 976.15nm) reflects to form an external cavity, achieving wavelength locking and spectral narrowing. The wavelength-locked and spectrally narrowed laser is output through an airtight optical window. When the module of Example 1 operates at a low temperature (e.g., -25℃), the wavelength of the semiconductor laser chip 36 exhibits a blue shift. The free-running spectral wavelength of the chip at low temperature is around 976nm (wavelength temperature coefficient is 0.3nm / ℃). When the temperature decreases, the two wavelengths of the dual-wavelength selective volume Bragg grating 34 exhibit blue shifts to 990.85nm and λ, respectively. L =976nm (grating wavelength temperature coefficient is 0.01nm / ℃), wavelength λ of dual-wavelength selective bulk Bragg grating 34 at low temperature. L =976nm, matching the wavelength of the free spectrum of semiconductor laser chip 36 at low temperature to achieve wavelength locking and spectral narrowing. At room temperature, the free-operating spectral design wavelength of semiconductor laser chip 36 is 991nm, and the wavelength λ of the dual-wavelength selective volume Bragg grating 34 is [missing information]. H =991nm is the adjustment wavelength.

[0038] Example 2: Fiber Coupled Output Module Based on Volume Bragg Grating Please see Figure 4 This embodiment adds an optical fiber coupling output structure based on embodiment 1, and is suitable for pump source applications that require flexible transmission.

[0039] like Figure 4 As shown, the module in this embodiment includes: a housing 41, a heat sink with a low coefficient of thermal expansion 42, an airtight optical window 43, a dual-wavelength selective volume Bragg grating 46 (with the same function as in Embodiment 1), a focusing optical component 45, a semiconductor laser chip 48, a collimating optical component 47, a sealing cover plate 49, and an output optical fiber 44.

[0040] The difference from Example 1 is as follows: Inside the airtight optical window 43 (or integrated into the inside of the window), there is a focusing optical component 45, which may be composed of one or more spherical cylindrical lenses, used to converge the collimated beam after wavelength locking and spectral narrowing.

[0041] The output fiber 44 is a large-core multimode fiber, and its input end face is located near the focal point of the focusing optical component 45. It is connected to the tube shell 41 through a fiber coupler.

[0042] During operation, the laser emitted from the semiconductor laser chip 48 is collimated by the collimating optical component 47, locked by the dual-wavelength selective volume Bragg grating 46, and then coupled into the output optical fiber 44 through the focusing optical component 45 to achieve fiber output.

[0043] The wavelength design and locking principle in this embodiment is exactly the same as in Embodiment 1.

[0044] Example 3: Module based on dual-wavelength selective fiber Bragg grating Please see Figure 5 The difference between this embodiment and embodiments 1 and 2 is that a dual-wavelength selective fiber grating 54 is used instead of a bulk Bragg grating as an external cavity feedback element, thereby achieving wavelength locking, spectral narrowing and fiber output.

[0045] like Figure 5 As shown, the module in this embodiment includes: a housing 51, a low thermal expansion coefficient heat sink 52, an airtight optical window 53, a dual-wavelength selective fiber grating 54, a coupling lens group 55, a semiconductor laser chip 56, and a sealing cover 57. The dual-wavelength selective fiber grating 54 consists of two fiber gratings with different Bragg wavelengths written into the fiber core, corresponding to the room-temperature tuning wavelength λ2 and the low-temperature operating wavelength λ1, respectively. The input end face of this fiber grating 54 is beveled or coated with an anti-reflection film to reduce end-face feedback interference.

[0046] The coupling lens group 55 consists of one or more lenses and is used to efficiently couple the emitted laser from the semiconductor laser chip 56 into the fiber core of the dual-wavelength selective fiber grating 54.

[0047] Wavelength locking principle: At room temperature, the free-running wavelength of chip 56 aligns with λ2 of fiber optic grating 54, and some light is reflected back to the chip to form an external cavity, achieving wavelength locking and spectral narrowing. At low temperature, the chip wavelength blue-shifts and automatically aligns with λ1 of fiber optic grating 54, achieving low-temperature wavelength locking. The locked laser light is directly output through the output end of fiber optic grating 54.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A wavelength-locked pump laser module operating at low temperature, characterized in that, include: Tube shell; A heat sink with a low coefficient of thermal expansion is fixed to the bottom surface inside the tube shell; A semiconductor laser chip is fixed to the upper surface of the heat sink with a low coefficient of thermal expansion for emitting a laser beam. A collimating optical component is fixed to the upper surface of the low thermal expansion coefficient heat sink and located in the optical path of the emitted laser beam of the semiconductor laser chip, for collimating the laser beam; A dual-wavelength selective reflection element is fixed on the upper surface of the low thermal expansion coefficient heat sink and located behind the outgoing optical path of the collimating optical component. It is placed opposite the semiconductor laser chip along the optical path to form an external cavity feedback structure. A sealed optical window is placed on the side wall or end wall of the tube shell and located in the optical path of the output laser after being acted upon by the dual-wavelength selective reflection element; And a sealing cover plate, which is sealed to the tube shell, and hermetically installs the low thermal expansion coefficient heat sink, semiconductor laser chip, collimating optical components and dual wavelength selective reflection element inside the tube shell; The dual-wavelength selective reflection element has a second reflection wavelength λ2 for adjustment and locking at room temperature and a first reflection wavelength λ1 for operation locking at low temperature; the wavelength difference Δλ between the first reflection wavelength λ1 and the second reflection wavelength λ2 satisfies: Δλ = (T room -T low ) λ T-chip T low T is the preset low-temperature operating temperature. room For room temperature assembly, λ T-chip The temperature coefficient of the center wavelength of the semiconductor laser chip is denoted as .

2. The wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The dual-wavelength selective reflection element is selected from one of the following: a volume Bragg grating, a volume Bragg grating combined with a coating element, a fiber optic grating, or an optical filter element with discrete dual reflection peaks.

3. The wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The wavelength temperature coefficient of the semiconductor laser chip is greater than that of the dual-wavelength selective reflection element, so that at the room temperature adjustment temperature T room With the aforementioned low-temperature operating temperature T low When the wavelengths change, the drift of the free-running wavelength of the semiconductor laser chip is greater than the drift of the reflected wavelength of the dual-wavelength selective reflective element.

4. The wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The aforementioned low-temperature operating temperature T low The range is -50℃ to 5℃, and the ambient temperature adjustment temperature T is... room The temperature ranges from 15°C to 30°C.

5. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, It also includes a focusing optical component and an output optical fiber; the focusing optical component is fixed on the upper surface of the low thermal expansion coefficient heat sink or inside the tube shell, and is located between the sealed optical window and the dual-wavelength selective reflection element or inside the sealed optical window; the input end of the output optical fiber is connected to the tube shell and is located at the focal point of the output optical path of the focusing optical component, so that the output laser after feedback by the dual-wavelength selective reflection element is coupled into the output optical fiber through the collimating optical component, the dual-wavelength selective reflection element and the focusing optical component in sequence to realize laser output.

6. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The tube shell is filled with dry gas and is hermetically sealed through the sealed optical window and sealing cover to prevent condensation inside the module in environments below 5°C.

7. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The semiconductor laser chip is an FP cavity chip, with a high-reflectivity film deposited on the rear cavity surface and an anti-reflection film deposited on the light-emitting surface.

8. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The free-running wavelength of the semiconductor laser chip at room temperature is aligned with the second reflected wavelength λ2; at low temperature, the free-running wavelength of the semiconductor laser chip is blue-shifted and aligned with the first reflected wavelength λ1.

9. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, The semiconductor laser chip can be one or more. When there are multiple semiconductor laser chips, they are combined spatially or polarized by lenses and mirrors, and then together with the dual-wavelength selective reflection element to form an external cavity feedback structure. Alternatively, the multiple semiconductor laser chips can each form an external cavity feedback structure with their respective dual-wavelength selective reflection element, and then be combined and output through a beam combining element.

10. A wavelength-locked semiconductor laser module operating at low temperature according to claim 1, characterized in that, After the dual-wavelength selective reflective element is assembled and adjusted at room temperature, it is fixed to the upper surface of the heat sink with a low coefficient of thermal expansion by means of ultraviolet thermosetting adhesive or welding. No secondary fine-tuning is required in a low-temperature environment, and the required wavelength is automatically locked at low temperatures.

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