A wavelength-locked semiconductor laser

Abstract

The present application discloses a wavelength-locked semiconductor laser, comprising: a semiconductor laser chip, a collimating lens, a re-collimating lens, a sampling mirror, and a wavelength-locking module. The collimating lens and the re-collimating lens are sequentially arranged along the laser beam emission direction of the semiconductor laser chip. The sampling mirror is used to sample the spot edge of the laser beam after passing through the re-collimating lens and reflect it to the wavelength-locking module. The feedback beam returns to the semiconductor laser chip after passing through the sampling mirror, the focal point of the re-collimating lens, the re-collimating lens, and the collimating lens in sequence. The wavelength-locked semiconductor laser disclosed in the present application can significantly reduce the power density on the wavelength-locking module, improve the temperature characteristics of the wavelength-locking module; avoid the absorption of the feedback beam by the non-light-emitting area at the edge of the semiconductor laser chip, reduce the cavity surface temperature, and greatly improve the laser life and reliability; improve the output beam quality of the laser, and enhance the stability and reliability of the semiconductor laser.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a wavelength-locked semiconductor laser. Background Art

[0002] High-power gas lasers have high power and good beam quality, and are widely used in different fields. Since the absorption peak of gas lasers is relatively narrow, usually the absorption region width (FWHM) is much less than 1 nm, it is necessary to lock the wavelength of the semiconductor laser diode to stably output the central wavelength and narrow the output spectral width. Otherwise, the pump light absorption efficiency is low and the energy loss is serious. The unabsorbed energy will be reflected multiple times inside the laser, causing the temperature of the laser to rise and even burning out the laser.

[0003] In a conventional external cavity wavelength-locking structure, a volume Bragg grating (VBG) needs to be placed inside the pump source, or a volume grating needs to be placed at the front end of each chip. The locking effect of the volume grating, that is, the central wavelength of the locked spectrum, changes with the operating current of the laser and the laser temperature (the change amount is about 0.03 nm / °C). In some fields that require stable output of the central wavelength, such as pumping alkali metal gas lasers, since the absorption peak is relatively narrow (FWHM is approximately 0.3 nm), it is necessary to actively control the temperature of the volume grating. Therefore, for a high-power narrow-linewidth wavelength-locked semiconductor laser using a volume grating, if precise control of the output wavelength and spectral width is required, precise temperature control of the volume grating is needed, and the control difficulty increases with the increase in the number of pump sources. Summary of the Invention

[0004] To solve one or more of the above problems, this application proposes a wavelength-locked semiconductor laser.

[0005] According to one aspect of this application, there is provided a wavelength-locked semiconductor laser, including a semiconductor laser chip, a collimating lens, a re-collimating lens, a sampling mirror, and a wavelength-locking module. The collimating lens and the re-collimating lens are sequentially arranged along the laser beam output direction of the semiconductor laser chip. The sampling mirror is arranged on the side of the re-collimating lens away from the collimating lens. The sampling mirror is used to sample the spot edge of the laser beam after passing through the re-collimating lens. The sampling mirror can collect a preset proportion of the laser beam and reflect the collected sampling beam to the wavelength-locking module. The wavelength-locking module is used to perform wavelength selection on the incident sampling beam and feedback a beam of a specific wavelength. The feedback beam emitted by the wavelength-locking module passes through the sampling mirror, the focus of the re-collimating lens, the re-collimating lens, and the collimating lens in sequence and then returns to the semiconductor laser chip.

[0006] In some embodiments, the collimating lens is a circular lens, the light-emitting cavity surface of the semiconductor laser chip is disposed on the focal plane of the collimating lens, and the collimating lens is used for collimating the laser beam in the fast axis direction and expanding the divergence angle in the slow axis direction; or,

[0007] The collimating lens includes a first cylindrical lens and a second cylindrical lens. The first cylindrical lens and the second cylindrical lens are sequentially disposed along the light-emitting direction of the semiconductor laser chip. The first cylindrical lens is used for collimating the laser beam in the fast axis direction, and the second cylindrical lens is used for expanding the divergence angle of the laser beam in the slow axis direction.

[0008] In some embodiments, the focal length of the collimating lens is not greater than half of the Rayleigh range in the slow axis direction of the output light of the semiconductor laser chip.

[0009] In some embodiments, the re-collimating lens is a cylindrical lens. Denote the Rayleigh range in the slow axis direction of the laser beam after passing through the collimating lens as Z R1 The focal length of the re-collimating lens is n times Z R1 where n is an integer not less than 20.

[0010] In some embodiments, the distance between the collimating lens and the re-collimating lens is the sum of the focal length of the collimating lens and the focal length of the re-collimating lens.

[0011] In some embodiments, the horizontal distance between the center of the sampling mirror and the plane where the re-collimating lens is located is not less than twice the focal length of the re-collimating lens and not greater than one quarter of the Rayleigh range in the slow axis direction of the laser beam after passing through the re-collimating lens.

[0012] In some embodiments, the proportion of the laser beam collected by the sampling mirror is 5% - 50%.

[0013] In some embodiments, the wavelength locking module is a volume grating, a reflective surface grating, or a transmissive surface grating and a mirror disposed behind the transmissive surface grating.

[0014] In some embodiments, assume there is a virtual wavelength locking module. The virtual wavelength locking module is axisymmetric with the wavelength locking module about the sampling mirror. Let the angle between the sampling beam incident on the wavelength locking module and the sampling beam exiting from the wavelength locking module be θ, the angle between the sampling mirror and the optical axis be β, and the angle between the straight line where the incident surface of the virtual wavelength locking module is located and the straight line where the incident surface of the wavelength locking module is located be α. Then β = 90 - α / 2 - θ / 2.

[0015] In some embodiments, there is a virtual incident point on the virtual wavelength locking module. The virtual incident point is axisymmetric with the incident point of the sampling beam on the wavelength locking module about the sampling mirror.

[0016] The expression for the included angle θ between the sampling beam of the incident wavelength locking module and the sampling beam exiting from the wavelength locking module is as follows:

[0017]

[0018] In the formula, f 1 represents the focal length of the collimating lens, f 2 represents the focal length of the re-collimating lens, w 0 represents the spot width in the slow axis direction of the laser beam emitted from the semiconductor laser chip, L 1 represents the horizontal distance between the incident point of the sampling beam on the sampling mirror and the re-collimating lens, L 2 represents the horizontal distance between the incident point of the sampling beam on the sampling mirror and the virtual incident point on the virtual wavelength locking module.

[0019] A wavelength-locked semiconductor laser disclosed in the present application uses optical elements to perform edge spot sampling on the expanded spot of the output cavity surface of the semiconductor laser chip, enabling the low-power spot at the edge of the laser beam to be incident on the wavelength locking module for wavelength selection. This can significantly reduce the power density on the wavelength locking module, improve the temperature characteristics of the wavelength locking module, reduce the drift of the semiconductor laser wavelength over time and the internal temperature gradient of the wavelength locking module without active temperature control; feedback the edge beam after wavelength selection to the center of the semiconductor laser chip cavity surface, avoiding absorption of the feedback beam by the non-emitting area at the edge of the semiconductor laser chip, reducing the cavity surface temperature, and greatly improving the lifetime and reliability of the laser; sampling at the edge of the spot reduces the output beam size and improves the output beam quality of the laser. Since the spot size of the output cavity surface of the semiconductor laser chip is controlled by the waveguide and the waveguide size does not change with the operating temperature and operating current, the sampled spot size will not change with temperature and current after the sampling ratio is determined, improving the stability and reliability of the semiconductor laser. Description of the Drawings

[0020] Figure 1 This is a top view of a wavelength-locked semiconductor laser provided by an embodiment of the present application.

[0021] Figure 2 This is an optical path diagram of the laser beam passing through the collimating lens when the collimating lens is a single circular lens in a wavelength-locked semiconductor laser provided by an embodiment of the present application.

[0022] Figure 3 This is an optical path diagram of the laser beam passing through the collimating lens when the collimating lens is two cylindrical lenses in a wavelength-locked semiconductor laser provided by an embodiment of the present application.

[0023] Figure 4An optical path diagram of a wavelength-locked semiconductor laser provided by an embodiment of the present application.

[0024] Figure 5 A top view of another wavelength-locked semiconductor laser provided by an embodiment of the present application.

[0025] Figure 6 A top view of another wavelength-locked semiconductor laser provided by an embodiment of the present application. Detailed implementation manners

[0026] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only a part of the embodiments of the present application, rather than all of the embodiments, and are only used to explain the present application, not to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application.

[0027] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "both ends", "both sides", "bottom", "top", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the elements referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present application. In addition, the terms "first", "second", "superior", "inferior", "main", "secondary", etc. are only used for descriptive purposes and can be simply used to more clearly distinguish different components, rather than indicating or implying relative importance.

[0028] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0029] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0030] Embodiment:

[0031] Refer to the attached drawings of the specification Figure 1, an embodiment of the present application provides a wavelength-locked semiconductor laser, which includes a semiconductor laser chip 1, a collimating lens 2, a re-collimating lens 3, a sampling mirror 4, and a wavelength-locking module 5.

[0032] Among them, the collimating lens 2 and the re-collimating lens 3 are sequentially arranged along the laser beam emission direction of the semiconductor laser chip 1.

[0033] The sampling mirror 4 is arranged on the side of the re-collimating lens 3 away from the collimating lens 2. The sampling mirror 4 is used to sample the spot edge of the laser beam after passing through the re-collimating lens. The sampling mirror 4 can collect a preset proportion of the laser beam. For the laser beam passing through the re-collimating lens 3, a part of it is incident on the sampling mirror 4, and after being reflected by the sampling mirror 4, it is used as a sampling beam to be incident on the wavelength-locking module 5, and the other part of the laser beam remains unchanged in direction.

[0034] The wavelength-locking module 5 is used for wavelength selection and feedbacks a beam of a specific wavelength. For the sampling beam incident on the wavelength-locking module 5, after being wavelength-locked by the wavelength-locking module 5, a feedback beam of a specific wavelength is emitted. The feedback beam sequentially passes through the sampling mirror 4, the focus of the re-collimating lens 3, the re-collimating lens 3, and the collimating lens 2 and then returns to the center of the semiconductor laser chip.

[0035] The collimating lens 2 is a positive lens, that is, a lens with a positive focal length.

[0036] In an alternative embodiment, the collimating lens 2 can be a circular lens. The light-emitting cavity surface of the semiconductor laser chip 1 is arranged on the focal plane of the collimating lens 2. The collimating lens 2 is used to collimate the laser beam emitted by the semiconductor laser chip 1 in the fast axis direction and expand the divergence angle in the slow axis direction. Refer to the attached Figure 2 , the attached Figure 2 shows the optical path diagram of the laser beam passing through the collimating lens 2 when the collimating lens 2 is a circular lens, where (a) is a top view and (b) is a side view.

[0037] In an alternative embodiment, the collimating lens 2 can be two cylindrical lenses. The collimating lens 2 can include a first cylindrical lens 21 and a second cylindrical lens 22. The first cylindrical lens 21 and the second cylindrical lens 22 are sequentially arranged along the light-emitting direction of the semiconductor laser chip 1. The first cylindrical lens 21 is used to collimate the laser beam in the fast axis direction, and the second cylindrical lens 22 is used to expand the divergence angle of the laser beam in the slow axis direction. Refer to the attached Figure 3 , the attached Figure 3 shows the optical path diagram of the laser beam passing through the collimating lens 2 when the collimating lens 2 is two cylindrical lenses, where (a) is a top view and (b) is a side view.

[0038] When the divergence angle of the laser beam after passing through the collimating lens 2 is greater than the divergence angle of the laser beam before entering the collimating lens 2, that is, the focal length of the collimating lens 2 is not greater than half of the Rayleigh interval length in the slow axis direction of the laser beam output by the semiconductor laser chip 1. When the collimating lens 2 is two cylindrical lenses, the focal length of the second cylindrical lens 22 is not greater than half of the Rayleigh interval length in the slow axis direction of the laser beam output by the laser chip.

[0039] The length of the Rayleigh interval is denoted as Z R , Z R =w 1 / θ 1 , where w 1 Indicates the spot width, the intensity becomes 1 / e of the peak intensity 2 The corresponding spot width is half, θ 1 Indicates the light spot divergence angle, and the intensity becomes 1 / e of the peak intensity 2 The corresponding spot divergence angle is half.

[0040] In this embodiment, the slow axis w of the laser beam emitted by the semiconductor laser chip 1 is 1 =100μm,θ 1 =5° laser beam as an example, the Rayleigh interval length is 1.1mm, that is, the focal length of the collimating lens 2 is no more than 0.55mm. Assume that the focal length of the collimating lens 2 is f 1 , then the Rayleigh interval length after passing through collimating lens 2 is .

[0041] In this embodiment, the fast axis w of the laser beam emitted by the semiconductor laser chip 1 is set to 1 =1μm,θ 1 =28°, slow axis w 1 =100μm,θ 1 =5°. When the collimating lens 2 is a single circular lens with a focal length of 0.5 mm, the fast axis beam of the laser beam emitted by the semiconductor laser chip 1 passes through the collimating lens 2. 1 From 28° to 0.1°, the Rayleigh interval length of the fast axis beam changes from 1.6μm to 152.7mm; after the slow axis beam passes through the collimating lens 2, θ 1 It expands from 5° to 11.5°, the Rayleigh interval length of the slow-axis beam changes from 1.1mm to 0.2mm, the spot size changes, and the slow-axis spot is imaged from 2mm to infinity from the light-emitting cavity surface of the semiconductor laser chip 1, and the size of the image is proportional to the distance.

[0042] When the transmission distance of the laser beam after passing through the collimating lens 2 is much greater than the Rayleigh interval length, the distribution of the laser beam passing through the collimating lens 2 in the slow axis direction is consistent with the distribution of the laser beam emitted by the semiconductor laser chip 1 in the slow axis direction.

[0043] In an alternative embodiment, the re-collimating lens 3 is a cylindrical lens. Denote the Rayleigh range in the slow axis direction of the laser beam after passing through the collimating lens 2 as Z R1 , then the focal length of the re-collimating lens is n times Z R1 , where n is an integer not less than 20. And the distance between the collimating lens 2 and the re-collimating lens 3 is the sum of the focal lengths of the collimating lens 2 and the re-collimating lens 3

[0044] In this embodiment, n is taken as 50, and the focal length of the re-collimating lens 3 is set to 10 mm. The length of the slow axis Rayleigh range of the laser beam after passing through the re-collimating lens 3 is 458.4 mm, and the spot size is approximately unchanged within a length of 100 mm after passing through the re-collimating lens 3

[0045] The horizontal distance between the center of the sampling mirror 4 and the plane where the re-collimating lens 3 is located is not less than twice the focal length of the re-collimating lens 3 and not greater than one-fourth of the Rayleigh range in the slow axis direction of the laser beam after passing through the re-collimating lens 3

[0046] This is because the spot size is approximately unchanged within 1 / 4 of the length of the slow axis Rayleigh range in the slow axis direction of the laser beam after passing through the re-collimating lens 3. Therefore, the sampling mirror 4 can collect the edge beam of the laser beam for wavelength locking, and since the spot size remains unchanged within this range, the sampling ratio can also remain unchanged after the sampling mirror 4 is fixed

[0047] Thus, through the settings of the collimating lens 2 and the re-collimating lens 3, it is possible to avoid the situations of inability to sample or over-sampling caused by the divergence angle of the beam in the slow axis direction of the semiconductor laser chip 1 changing with the operating temperature and current. Since the divergence angle of the beam in the slow axis direction of the semiconductor laser chip 1 changes with the operating temperature and current, if the collimating lens 2 and the re-collimating lens 3 are not set, the divergence angle decreases in the case of low current or low temperature, resulting in no beam incident on the sampling mirror 4, unable to sample and unable to perform wavelength locking. In the case of high current or high temperature, the divergence angle of the semiconductor laser chip 1 increases, resulting in an excessive beam incident on the sampling mirror 4, over-sampling, and damaging the chip. Moreover, there is no corresponding relationship between the beam incident on the sampling mirror 4 and the laser beam emitted by the laser chip, and the feedback beam will cover the entire light-emitting cavity surface of the semiconductor laser chip, and there will be absorption at the edge part, increasing the failure risk of the semiconductor laser chip 1

[0048] The sampling mirror 4 is partially disposed on the optical path of the laser beam, that is, the sampling mirror 4 is disposed at the edge of the light spot of the laser beam after passing through the re-collimating lens 3. According to the different proportions of the laser beam collected by the set sampling mirror, the overlapping area of the sampling mirror 4 and the light spot of the laser beam after passing through the re-collimating lens 3 is different. The larger the proportion of the laser beam collected by the sampling mirror 4, the larger the overlapping area of the sampling mirror 4 and the light spot of the laser beam after passing through the re-collimating lens 3.

[0049] In an alternative embodiment, the sampling mirror 4 is a total reflection mirror. The proportion of the laser beam collected by the sampling mirror 4 can be set to 5% - 50%.

[0050] Since the light-emitting cavity surface of the semiconductor laser chip 1 is located at the focal plane of the collimating lens 2, and the focal length of the collimating lens 2 is less than the Rayleigh interval length of the laser beam emitted by the semiconductor laser chip 1, the laser beam emitted by the semiconductor laser chip 1 is approximately parallel light and parallel to the optical axis. Therefore, assuming that a laser ray exits from the edge of the semiconductor laser chip 1, since the laser ray is parallel to the optical axis, the laser ray passes through the focal point on the side of the collimating lens 2 close to the re-collimating lens 3, and then passes through the re-collimating lens 3 and becomes parallel to the optical axis again. The laser ray parallel to the optical axis is sampled by the sampling mirror 4, wavelength selection is performed in the wavelength locking module 5, and the feedback ray emitted from the wavelength locking module 5 passes through the sampling mirror 4, the focal point of the re-collimating lens 3, and the re-collimating lens 3 in sequence. The feedback ray after passing through the re-collimating lens 3 is parallel to the optical axis, and then passes through the collimating lens 2 and is incident on the center of the light-emitting cavity surface of the semiconductor laser chip 1. When the ray emitted from the wavelength locking module 5 is a feedback beam, the center of the feedback beam passes through the focal point of the re-collimating lens 3.

[0051] Thus, by setting the sampling mirror 4, it is possible to prevent the wavelength locking module 5 from directly contacting the high-power laser beam, and to prevent the notch or low-quality coating on the edge of the wavelength locking module 5 from increasing laser absorption and causing a change in the central wavelength.

[0052] Suppose there is a virtual wavelength locking module 6, and the virtual wavelength locking module 6 satisfies the following conditions: when there is no sampling mirror 4, the ray emitted from the edge of the semiconductor laser chip 1 can pass through the collimating lens 2, the focal point of the collimating lens 2, and the re-collimating lens 3 in sequence and then enter the virtual wavelength locking module 6, and the feedback ray emitted from the virtual wavelength locking module 6 can pass through the focal point of the re-collimating lens 3, the re-collimating lens 3, and the collimating lens 2 in sequence and then return to the center of the light-emitting cavity surface of the semiconductor laser chip 1.

[0053] Refer to the attached Figure 4, the virtual wavelength locking module 6 is axisymmetric with the wavelength locking module 5 with respect to the sampling mirror 4. There is a virtual incident point on the virtual wavelength locking module 6, and the virtual incident point is axisymmetric with the incident point of the sampling beam on the wavelength locking module 5 with respect to the sampling mirror 4.

[0054] Let the angle between the sampling beam incident on the wavelength locking module 5 and the sampling beam exiting from the wavelength locking module 5 be θ, and θ is also the angle between the sampling beam incident on the virtual wavelength locking module 6 and the sampling beam exiting from the virtual wavelength locking module 6. Let the angle between the sampling mirror 4 and the optical axis 7 be β, and the angle between the straight line where the incident surface of the virtual wavelength locking module 6 is located and the straight line where the incident surface of the wavelength locking module 5 is located be α. Then β = 90 - α / 2 - θ / 2.

[0055] Among them, the expression of the angle θ between the sampling beam incident on the wavelength locking module 5 and the sampling beam exiting from the wavelength locking module 5 is as follows:

[0056]

[0057] In the formula, f 1 represents the focal length of the collimating lens 2, f 2 represents the focal length of the re-collimating lens 3, w 0 represents the spot width in the slow axis direction of the laser beam emitted from the semiconductor laser chip 1, L 1 represents the horizontal distance between the incident point of the sampling beam on the sampling mirror 4 and the re-collimating lens 3, L 2 represents the horizontal distance between the incident point of the sampling beam on the sampling mirror 4 and the virtual incident point on the virtual wavelength locking module 6.

[0058] In an alternative embodiment, the wavelength locking module 5 can be a volume grating, or a reflective surface grating 51, or a transmissive surface grating 52 and a mirror 53 disposed behind the transmissive surface grating 52.

[0059] Refer to the attached Figure 1 , the wavelength locking module 5 is a volume grating, and the reflectivity of the volume grating is 50% - 100%.

[0060] Refer to the attached Figure 5 , the wavelength locking module 5 is a reflective surface grating 51.

[0061] Refer to the attached Figure 6, the wavelength locking module 5 includes a transmissive surface grating 52 and a mirror 53 disposed behind the transmissive surface grating 52. The sampling beam is incident on the transmissive surface grating 52, diffracted and then incident on the mirror 53. The feedback beam emitted from the mirror 53 is emitted after passing through the transmissive surface grating 52. There is an included angle between the feedback beam emitted from the transmissive surface grating 52 and the sampling beam incident on the transmissive surface grating 52 from the sampling mirror 4.

[0062] The feedback beam passes through the sampling mirror 4, the re-collimating lens 3 and the collimating lens 2 in sequence, and then is incident on the central region of the light-emitting cavity surface of the semiconductor laser chip 1. The area of the central region of the light-emitting cavity surface of the semiconductor laser chip 1 does not exceed 1 / 2 of the total area of the light-emitting cavity surface, and the central position of the central region of the light-emitting cavity surface of the semiconductor laser chip 1 coincides with the central position of the light-emitting cavity surface.

[0063] A wavelength-locked semiconductor laser disclosed in the present application, through the setting of optical elements, samples the edge spot after the output cavity surface spot of the semiconductor laser chip is enlarged, so that the low-power spot at the edge of the laser beam is incident on the wavelength locking module for wavelength selection, which can greatly reduce the power density on the wavelength locking module, improve the temperature characteristics of the wavelength locking module, and reduce the drift of the semiconductor laser wavelength over time and the internal temperature gradient of the wavelength locking module without active temperature control; the edge beam after wavelength selection is fed back to the center of the semiconductor laser chip cavity surface, avoiding the absorption of the feedback beam by the non-light-emitting area at the edge of the semiconductor laser chip, reducing the cavity surface temperature, and greatly improving the laser life and reliability; sampling at the edge of the spot reduces the output beam size and improves the output beam quality of the laser. Since the output cavity surface spot size of the semiconductor laser chip is controlled by the waveguide and the waveguide size does not change with the working temperature and working current, after the sampling ratio is determined, the sampled spot size does not change with temperature and current, improving the stability and reliability of the semiconductor laser.

[0064] The above are only optional embodiments of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A wavelength-locked semiconductor laser, characterized in that: It includes semiconductor laser chip, collimating lens, re-collimating lens, sampling reflector and wavelength locking module. The collimating lens and the re-collimating lens are sequentially arranged along the laser beam emission direction of the semiconductor laser chip, The sampling reflector is arranged on a side of the re-collimating lens away from the collimating lens, and is used to sample the edge of the spot of the laser beam after passing through the re-collimating lens. The sampling reflector can collect a preset proportion of the laser beam and reflect the collected sampling beam to the wavelength locking module. The wavelength locking module is used to select the wavelength of the incident sampling light beam and feed back a light beam of a specific wavelength. The feedback light beam emitted by the wavelength locking module passes through the sampling reflector, the focus of the re-collimating lens, the re-collimating lens and the collimating lens in sequence and then returns to the semiconductor laser chip. The wavelength locking module is a volume grating or a reflective surface grating or a transmissive surface grating and a reflector arranged behind the transmissive surface grating.

2. A wavelength-locked semiconductor laser according to claim 1, characterized in that: The collimating lens is a circular lens, the light emitting cavity surface of the semiconductor laser chip is arranged on the focal plane of the collimating lens, and the collimating lens is used to collimate the laser beam in the fast axis direction and expand the divergence angle in the slow axis direction; or, The collimating lens includes a first cylindrical lens and a second cylindrical lens, which are sequentially arranged along the light emitting direction of the semiconductor laser chip. The first cylindrical lens is used to collimate the laser beam in the fast axis direction, and the second cylindrical lens is used to expand the divergence angle of the laser beam in the slow axis direction.

3. A wavelength-locked semiconductor laser according to claim 1, characterized in that: The focal length of the collimating lens is not greater than half of the Rayleigh interval in the slow axis direction of the output light of the semiconductor laser chip.

4. The wavelength-locked semiconductor laser according to claim 1, characterized in that: The re-collimating lens is a cylindrical lens, and the Rayleigh interval of the laser beam in the slow axis direction after passing through the collimating lens is recorded as Z R1 , the focal length of the re-collimating lens is n times Z R1 , n is an integer not less than 20.

5. The wavelength-locked semiconductor laser according to claim 1, characterized in that: The distance between the collimating lens and the re-collimating lens is the sum of the focal length of the collimating lens and the focal length of the re-collimating lens.

6. The wavelength-locked semiconductor laser according to claim 1, characterized in that: The horizontal distance between the center of the sampling reflector and the plane where the re-collimating lens is located is not less than twice the focal length of the re-collimating lens, and is not greater than one quarter of the Rayleigh interval in the slow axis direction of the laser beam after passing through the re-collimating lens.

7. The wavelength-locked semiconductor laser according to claim 1, characterized in that: The proportion of the laser beam collected by the sampling reflector is 5%-50%.

8. The wavelength-locked semiconductor laser according to claim 1, characterized in that: Assume that there is a virtual wavelength locking module, and the virtual wavelength locking module is symmetrical with the wavelength locking module about the sampling reflector axis. Assume that the angle between the sampling beam incident on the wavelength locking module and the sampling beam emitted from the wavelength locking module is θ, the angle between the sampling reflector and the optical axis is β, and the angle between the straight line where the incident surface of the virtual wavelength locking module is located and the straight line where the incident surface of the wavelength locking module is located is α, then β=90-α / 2-θ / 2.

9. The wavelength-locked semiconductor laser according to claim 8, characterized in that: There is a virtual incident point on the virtual wavelength locking module, and the virtual incident point and the incident point of the sampling beam on the wavelength locking module are symmetrical about the sampling reflector axis. The expression of the angle θ between the sampling beam incident on the wavelength locking module and the sampling beam emitted from the wavelength locking module is as follows: Wherein, f1 represents the focal length of the collimating lens, f2 represents the focal length of the re-collimating lens, w0 represents the spot width in the slow axis direction of the laser beam emitted by the semiconductor laser chip, L1 represents the horizontal distance between the incident point of the sampling beam on the sampling reflector and the re-collimating lens, and L2 represents the horizontal distance between the incident point of the sampling beam on the sampling reflector and the virtual incident point on the virtual wavelength locking module.

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