Semiconductor laser module

Abstract

The application provides a semiconductor laser module, comprising: a semiconductor laser comprising a light-emitting cavity surface; a mirror comprising a light-incident end surface; and an optical element arranged between the light-emitting cavity surface and the light-incident end surface, used for guiding light emitted by the semiconductor laser to the light-incident end surface; wherein the optical element comprises a light-incident surface opposite to the light-emitting cavity surface, a light-emitting surface opposite to the light-incident end surface, and a tapered outer surface; the tapered outer surface is coated with a film layer with a refractive index varying along a first direction or a second direction, the first direction is an extension direction of the light-incident surface to the light-emitting surface, and the second direction is perpendicular to the first direction; and the outer diameter of the optical element gradually decreases along a direction from the light-incident surface to the light-emitting surface. The application can realize multi-directional stray light suppression and improve the reliability and performance of the semiconductor laser.

Description

Technical Field

[0001] This application relates to the field of semiconductor laser technology, and more specifically, to a semiconductor laser module. Background Technology

[0002] In semiconductor laser chip module packaging, the output laser light is often reflected by interfaces such as the internal metal casing and fiber end face, forming backflow stray light that returns to the semiconductor laser cavity surface. This stray light not only causes a local temperature increase at the semiconductor laser cavity surface, interfering with the stability of the laser mode, but may also accelerate the aging of the semiconductor laser chip under long-term effects and even lead to its sudden burnout. Furthermore, the multiple reflections and scattering of stray light within the packaging cavity also introduce additional optical noise, affecting the quality and stability of the output beam.

[0003] Furthermore, as semiconductor lasers develop towards higher power and smaller package size, the generation path and reflection angle of stray light become more complex. Traditional packaging structures have limited ability to suppress stray light from multiple angles. Therefore, there is an urgent need for a packaging structure that can suppress stray light from multiple angles. Summary of the Invention

[0004] In view of this, this application provides a technical solution to the problem in the prior art where stray light is reflected from multiple angles in the packaging structure and returns to the cavity surface of the semiconductor laser, thereby causing degradation of the semiconductor laser's performance and reduction of its reliability.

[0005] The technical solution provided in this application is as follows:

[0006] This application provides a semiconductor laser module, including:

[0007] Semiconductor laser, including the light-emitting cavity surface;

[0008] A reflector with a light incident end face;

[0009] An optical element is disposed between the light-emitting cavity surface and the light-incident end surface, for guiding the light emitted from the semiconductor laser to the light-incident end surface;

[0010] The optical element has an incident surface opposite to the light-emitting cavity surface, an exit surface opposite to the light-incident end surface, and a conical outer surface.

[0011] The outer surface of the cone is coated with a film layer whose refractive index varies along a first direction or a second direction, wherein the first direction is the extension direction from the light incident surface to the light emitting surface, and the second direction is perpendicular to the first direction.

[0012] The outer diameter of the optical element gradually decreases along the direction from the light-incident surface to the light-exit surface.

[0013] Furthermore, the film is made of two materials, and the total thickness of the film is inversely proportional to the difference in refractive index between the two materials.

[0014] Furthermore, a lens is provided on the light-emitting surface of the optical element, and the size of the lens is on the subwavelength order, wherein the effective diameter of the lens matches the effective diameter of the laser spot formed by the semiconductor laser at the light-emitting surface.

[0015] Furthermore, the lens includes a hemispherical, aspherical, or diffractive optical surface.

[0016] Furthermore, when the lens is a hemispherical or aspherical surface, the hemispherical or aspherical surface protrudes from the light-incident surface in the direction of extension of the light-outceasing surface;

[0017] When the lens is a diffractive optical surface, the diffractive optical surface is a periodic or non-periodic microstructure.

[0018] Furthermore, a photonic crystal structure is formed on the conical outer surface of the optical element. The photonic crystal structure includes a one-dimensional photonic crystal structure, a two-dimensional photonic crystal structure, or a three-dimensional photonic crystal structure, and the morphologies of the one-dimensional photonic crystal structure, the two-dimensional photonic crystal structure, and the three-dimensional photonic crystal structure are different.

[0019] Furthermore, the photonic crystal structure includes a one-dimensional photonic crystal structure, which is a stacked structure. The stacked structure is formed by alternately stacking two medium materials with different refractive indices on the conical outer surface of the optical element in a direction perpendicular to the outer surface of the conical surface; or,

[0020] The photonic crystal structure includes a two-dimensional photonic crystal structure, which is an array structure. The array structure is etched onto the outer surface of the cone, and the surface of the array structure is uneven.

[0021] The photonic crystal structure includes a three-dimensional photonic crystal structure, which is a material with a three-dimensional periodic refractive index change prepared on the conical outer surface of the optical element.

[0022] Furthermore, the film layer consists of two layers, formed by stacking a first film layer material and a second film layer material. Both the first film layer material and the second film layer material are one of tantalum pentoxide, silicon dioxide, titanium dioxide, hafnium dioxide, aluminum oxide, or silicon nitride, and the first film layer material and the second film layer material are different.

[0023] Furthermore, the refractive index of the film varies along the radial direction of the outer surface of the cone, the film has a first refractive index in the central region of the outer surface of the cone, and the refractive index of the film continuously decreases from the central region outward;

[0024] The doping concentrations of the two materials in the film layer vary along a radial gradient to achieve a continuous change in the refractive index of the film layer.

[0025] Furthermore, the light-emitting cavity surface of the semiconductor laser is in contact with the light-incident surface of the optical element, or there is a gap between the light-emitting cavity surface of the semiconductor laser and the light-incident surface of the optical element;

[0026] The light-incident surface of the optical element is coated with a thermally conductive material, or the light-exiting cavity surface of the semiconductor laser is coated with a thermally conductive material.

[0027] The solution provided in this application has the following beneficial effects:

[0028] 1. The semiconductor laser module provided in this application focuses the emitted light from the semiconductor laser by setting a conical optical element between the semiconductor laser and the mirror, suppressing stray light in the range of 0~90° along the emission direction of the emitted beam of the semiconductor laser; furthermore, the outer diameter of the optical element gradually decreases from its incident surface to its emission surface, which can control the size of the emitted beam, reduce the probability of reflected light coupling back to the emission cavity surface of the semiconductor chip, and also block stray light reflected back to the emission surface of the optical element in the 180° direction from other optical devices; furthermore, a film layer with a refractive index varying along a first direction or a second direction is deposited on the conical outer surface of the optical element, which can further focus the emitted light of the semiconductor laser along the optical axis and suppress Fresnel reflection.

[0029] 2. The semiconductor laser module provided in this application has an optical element with a light-emitting surface size on the subwavelength scale, which can control the size of the emitted beam, reduce the probability of reflected light coupling back to the light-emitting cavity surface of the semiconductor chip, and further block stray light reflected back from other optical devices to the light-emitting surface of the optical element in the 180° direction; at the same time, the light-emitting surface of the optical element is arc-shaped, which further compresses the emitted light spot of the laser.

[0030] 3. The semiconductor laser module provided in this application forms a photonic crystal structure on the coating of the outer wall of the tapered outer surface of the optical element. The photonic crystal structure is combined with the optical element to further suppress stray light reflected back to the semiconductor laser module at multiple angles such as 180° laterally. Ultimately, it suppresses stray light incident from a direction close to 360° and avoids it from being reflected to the output cavity surface of the semiconductor laser and causing an impact.

[0031] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the structure of a semiconductor laser module provided in one embodiment of this application;

[0034] Figure 2 This is a schematic diagram of the structure of a semiconductor laser module provided in another embodiment of this application;

[0035] Figure 3 This is a schematic diagram of the structure of a semiconductor laser module provided in one embodiment of this application, compared to... Figure 1 This figure shows the photonic crystal structure formed on the conical outer surface of the optical element;

[0036] Figure 4 This is a schematic diagram of the structure of a semiconductor laser module provided in another embodiment of this application, compared to... Figure 2 This figure shows the photonic crystal structure formed on the conical outer surface of the optical element;

[0037] Figure 5 This is a schematic diagram of the internal optical path of an optical element provided in an embodiment of this application. The photonic crystal structure on the conical outer surface of the optical element is not shown in this figure.

[0038] Figure 6 A curve showing the fit between the reflectivity of the film layer on the conical side surface of the optical element provided in the embodiments of this application and the wavelength of the emitted beam from the semiconductor laser.

[0039] Explanation of reference numerals in the attached figures:

[0040] 100 - Semiconductor laser; 101 - Emission cavity surface; 200 - Optical element; 201 - Lens; 202 - Incident surface; 203 - Emission surface; 300 - Mirror; 301 - Incident surface. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of this application, it should be noted that the terms "inner," "outer," "upper," "lower," "vertical," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, features in the following embodiments can be combined with each other.

[0046] In view of the shortcomings of the prior art, the technical solution of this application is proposed. The technical solution of this application will be described in detail below.

[0047] Please see Figures 1-2 , Figure 1 This is a schematic diagram of the structure of a semiconductor laser module provided in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a semiconductor laser module provided in another embodiment of this application.

[0048] The semiconductor laser includes a semiconductor laser 100, an optical element 200, and a reflector 300. The optical element 200 is disposed between the semiconductor laser 100 and the reflector 300.

[0049] The semiconductor laser 100 includes an output cavity surface 101 for generating laser light. The semiconductor laser 100 is a distributed feedback (DFB) laser or a distributed Bragg reflection (DBR) laser, and its output cavity surface 101 is coated with a reflective film, which can form a resonant cavity together with the grating structure inside the semiconductor laser 100, thereby generating laser light of a specific wavelength.

[0050] Optionally, the semiconductor laser 100 is a quantum well laser, whose active region includes a strained quantum well structure to reduce the threshold current and improve output efficiency. The semiconductor laser 100 can also be a mode-locked laser, which generates pulsed laser light in the time domain by introducing a modulator within its resonant cavity or utilizing the laser's own nonlinear effects to lock the phases of different longitudinal modes within the resonant cavity. The output cavity surface 101 of the semiconductor laser 100 is coated with an antireflection film, which has a low reflectivity to the laser, reducing cavity surface reflection, improving laser output efficiency, and suppressing cavity surface backlighting.

[0051] The reflector 300 has a light incident end face 301, which is inclined relative to the optical axis of the reflector 300 at an angle of 30° to 60°. The surface of the light incident end face 301 is a plane, a convex curved surface, or a concave curved surface. When it is a convex curved surface or a concave curved surface, the light incident end face 301 also has the ability to collimate or focus the incident light. The inclined end face can spatially separate the light path incident on the light incident end face 301 and the light path reflected from the light incident end face 301, preventing the light path from directly returning to the light source.

[0052] The optical element 200 is disposed between the light-emitting cavity surface 101 and the light-incident end surface 301, and is used to guide the light emitted from the semiconductor laser 100 to the light-incident end surface 301, thereby guiding and focusing the light beam. The optical element 200 has an incident surface 202 opposite to the light-emitting cavity surface 101, an emitting surface 203 opposite to the light-incident end surface 301, and a tapered outer surface, which is its outer surface. This tapered outer surface connects the incident surface 202 and the emitting surface 203 of the optical element 200. The outer diameter of the optical element 200 gradually decreases from the incident surface 202 to the emitting surface 203.

[0053] The optical element 200 is generally shaped like a truncated cone, and both the light-incident surface 202 and the light-exit surface 203 are planes perpendicular to the optical axis of the optical element 200. The angle between the outer conical surface of the optical element 200 and the optical axis of the optical element 200 is in the range of 6° to 10°, so as to guide and focus the emitted light from the semiconductor laser 100.

[0054] Please see Figure 5 , Figure 5 The internal optical path diagram of the optical element 200 provided in this embodiment illustrates that when parallel light emitted from the semiconductor laser 100 enters the optical element 200 through the incident surface 202, even if a few rays cannot exit from the emitting surface 203 of the optical element 200 due to incident angle deviation during reflection, they will undergo multiple reflections within the optical element 200 and have a chance to exit from the emitting surface 203. The inner wall of the optical element 200 is coated with an absorbing film or a high-scattering film. Furthermore, due to the gradually decreasing outer diameter structure of the optical element 200, the edge rays of the laser beam emitted from the emitting cavity surface 101 of the semiconductor laser 100 reach the conical inner wall of the optical element 200 earlier during propagation within the optical element 200. This allows for earlier absorption or scattering of non-ideal portions of the laser beam (such as higher-order modes and large-angle stray light), effectively reducing the risk of stray light contamination of the semiconductor laser module.

[0055] The outer conical surface of the optical element 200 is coated with a film layer whose refractive index varies along a first direction or a second direction. The first direction is the extension direction from the light-incident surface 202 to the light-emitting surface 203, and the second direction is perpendicular to the first direction. In one embodiment, the outer conical surface of the optical element 200 is coated with a film layer whose refractive index varies.

[0056] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a semiconductor laser module provided in one embodiment of this application. Figure 1 The optical element 200 shown is a cross-sectional schematic diagram. In this cross-sectional schematic diagram, the extension direction from the light-incident surface 202 to the light-exit surface 203 of the optical element 200 is defined as a first direction, and the extension direction perpendicular to the first direction is defined as a second direction. It can be understood that the first direction is parallel to the axial direction of the optical element 200. Figure 1As can be seen from this embodiment, the film layer on the conical outer surface of the optical element 200 is disposed along the second direction. Furthermore, in this embodiment, the material at the center of the optical element 200 is a high-refractive-index material. Extending along the second direction, the refractive index of this film layer material decreases sequentially from the center of the optical element 200 outwards. The high-refractive-index material at the center of the optical element 200 can be selected from materials with a refractive index difference of approximately 0.5, such as tantalum pentoxide. The low-refractive-index material on the outer surface can be silicon dioxide. By controlling the doping concentration of both materials, a film layer with varying refractive index is formed on the conical outer surface of the optical element 200. The thickness of the high-refractive-index material and the low-refractive-index material in this film layer is set to one-quarter of the wavelength of the emitted laser from the semiconductor laser 100, in order to generate a strong Bragg reflection effect at the target wavelength. The film layer can have different periodic structures at different radial positions on the conical outer surface of the optical element 200. For example, the film layer located at the center of the optical element 200 is configured to reflect incident light at a larger angle, while other low-refractive-index material films are configured to reflect incident light at a smaller angle, thereby achieving full-area, multi-angle incident stray light reflection suppression on the conical outer surface of the optical element 200. Furthermore, by adjusting the refractive index distribution of the film layer along the first direction, Fresnel reflection generated during beam propagation can be suppressed, while enhancing beam focusing, making the output beam spot more uniform and concentrated. This structure not only improves beam quality but also reduces energy loss caused by reflection, thereby further improving the overall efficiency and stability of the semiconductor laser module.

[0057] In another embodiment, please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of a semiconductor laser module provided in another embodiment of this application. Figure 2 The optical element 200 shown in the diagram is a cross-sectional view. Figure 2As can be seen from this embodiment, the film layer on the conical outer surface of the optical element 200 is disposed along the first direction, and in this embodiment, the refractive index of the film layer on the conical outer surface of the optical element 200 exhibits a periodic change along the first direction. Specifically, from the light-incident surface 202 to the light-exit surface 203 of the optical element 200, the refractive index of the film layer material is distributed in a manner that alternates between high and low refractive indices. Furthermore, the thickness of each alternating layer of the film layer is not constant, but varies according to preset conditions. Ultimately, the combined change in thickness and refractive index forms a film layer that presents an overall structure of alternating high and low refractive indices and a non-uniform symmetrical structure. For a positive beam emitted from the semiconductor laser 100 and propagating along the optical element 200 towards the reflector 300, when it is incident on the film layer, the alternating refractive index and non-uniform symmetrical thickness of the film layer can reduce Fresnel reflection, achieve a high anti-reflection effect, thereby reducing beam transmission loss and improving the overall optical power utilization of the semiconductor laser module. Simultaneously, for stray light reflected back from the reflector 300, the film layer can cause the stray light to scatter or deviate from its original path, thus dispersing its energy and preventing it from returning to the output cavity surface 101 of the semiconductor laser 100 to form harmful backlight, thereby ensuring the reliability of the semiconductor laser module. Similarly, the film layer can have different periodic structures at different axial positions on the conical outer surface of the optical element 200. For example, the film layer near the incident surface 202 is configured to reflect incident light at a larger angle, and the film layer near the output surface 203 is configured to reflect incident light at a smaller angle, thereby achieving full-area, multi-angle incident stray light reflection suppression on the conical outer surface of the optical element 200.

[0058] Preferably, the film layer can be deposited on the conical outer surface of the optical element 200 by physical vapor deposition or plasma-enhanced chemical vapor deposition. The film layer is configured to have a high reflection band at the operating wavelength of the semiconductor laser 100 and a high transmittance at wavelengths outside the high reflection band. A light-absorbing material layer can be added to the outermost side of the film layer to absorb non-operating light transmitted through the film layer.

[0059] Specifically, the film is made of two materials, and the total thickness of the film is inversely proportional to the difference in refractive index between the film materials.

[0060] Please see Figure 6 , Figure 6This is a fitting curve of the reflectivity of the film layer on the conical outer surface of the optical element provided in this application embodiment and the wavelength of the emitted beam from the semiconductor laser. Taking a wavelength of 915nm as an example, the reflectivity of the film layer is approximately 97%. If the emitted beam wavelength of the semiconductor laser 100 is 1200nm, the reflectivity can be increased by increasing the total thickness of the film layer. That is, by increasing the total thickness of the film layer, the fitting curve can be shifted to the right, ultimately achieving a reflectivity of 97% at a wavelength of 1200nm. It can be understood that if a high reflectivity is desired at other wavelengths, the reflectivity can also be controlled by adjusting the total thickness of the film layer. The film layer is made of two materials. When the total reflectivity of the film layer is constant, the total thickness of the film layer is inversely proportional to the difference in refractive indices of the two film layer materials. In other words, the smaller the difference in refractive indices of the two film layer materials, the larger the required total thickness of the film layer; conversely, the larger the difference in refractive indices of the two film layer materials, the smaller the required total thickness of the film layer. In actual production, materials with a refractive index difference range of 0.5 to 0.8 can be selected to prepare the film layer. This ensures both the total reflectivity of the film layer and a relatively thin total thickness, making it easier to manufacture. Generally, the total thickness of the film layer is set in the range of 1.1 μm to 1.7 μm.

[0061] In this embodiment, by providing a tapered optical element 200 with a gradually decreasing outer diameter from the incident surface 202 to the exit surface 203 between the semiconductor laser 100 and the reflector 300, the laser beam emitted from the semiconductor laser 100 can be gently and controllably compressed spatially, gradually reducing its divergence angle, guiding and focusing the laser beam, thereby improving the light utilization rate of the semiconductor laser module. It can also suppress stray light within the 0-90° range along the emission direction of the emitted beam from the semiconductor laser. The gradual decrease in the outer diameter of the optical element 200 from its incident surface 202 to its exit surface 203 allows for control of the size of the emitted beam. The conical optical element 200 reduces the probability of reflected light coupling back to the light-emitting cavity surface 101 of the semiconductor chip, and can also block stray light reflected back from other optical devices to the light-emitting surface 203 of the optical element in the 180° direction. At the same time, the conical optical element 200 can also make the light beam with a certain divergence angle emitted by the semiconductor laser 100 reach the conical outer surface of the conical optical element 200 faster during propagation. At this time, the inner wall coated with light-absorbing film or high-scattering film will actively absorb or diffusely reflect this part of the non-ideal light, and absorb or scatter it, effectively reducing the risk of the semiconductor laser module being contaminated by stray light.

[0062] Furthermore, by providing a film layer with a changing refractive index on the outer wall of the conical outer surface of the optical element 200, the Bragg reflection principle can be used to efficiently reflect light with a working wavelength of the semiconductor laser 100 within a specific angular range. This angular range covers the angle of stray light that may be incident on the conical outer surface, and the reflected stray light can be discharged from the optical path, improving the overall stability and reliability of the semiconductor laser module. When stray light is incident on the surface of the conical outer surface, its energy is reflected rather than absorbed, avoiding heat generation caused by absorption and the risk of material degradation, thus improving the thermal stability and reliability of the optical element 200 under high-power operating conditions.

[0063] In one embodiment, the light-emitting surface 203 of the optical element 200 is provided with a lens 201, and the size of the lens 201 is on the subwavelength order.

[0064] The lens 201 includes a hemispherical, aspherical, or diffractive optical surface. An aspherical surface can eliminate spherical errors, converting the laser beam into parallel light with small wavefront distortion and a near-close divergence angle, or a very small spot. A diffractive optical surface contains periodic or aperiodic microstructures, the size of which is on the order of the light wavelength. Wavefront shaping is achieved by introducing position-dependent phase modulation. When the lens 201 is a hemispherical surface, the hemispherical surface bulges from the incident surface 202 towards the light propagation direction of the exit surface 203. The center of the hemispherical surface is located inside or outside the optical element 200, and its radius of curvature is related to the refractive index of the body material of the optical element 200 and the required focal length. The lens 201 is a metalens integrated on the light-emitting surface 203 of the optical element 200. This metalens comprises multiple subwavelength nanostructure units arranged periodically or aperiodically on the light-emitting surface 203. The nanostructure units can be cylindrical, prismatic, conical, or ellipsoidal in shape, and are made of a high-refractive-index, low-loss dielectric material, such as amorphous silicon, silicon nitride, or titanium dioxide. The lens 201 and the light-emitting surface 203 of the optical element 200 can be integrally formed, i.e., directly etched or deposited on the substrate material of the light-emitting surface 203 of the optical element 200. Optionally, the lens 201 can also be a separate ultrathin optical device, bonded to the light-emitting surface 203 of the optical element 200 using nanometer-precision bonding technology. The size range of the lens 201 is 285 micrometers to 290 micrometers. The size of the lens 201 is matched with the effective diameter of the laser spot formed by the semiconductor laser 100 at the light-emitting surface 203. The ratio between the two is strictly controlled to be approximately 1:1.

[0065] In this embodiment, the optical element 200 first absorbs stray light from the original beam emitted by the semiconductor laser 100, filtering out stray light from higher-order modes and edges. Then, through the lens 201 located on the light-emitting surface 203 of the optical element 200, whose size is on the subwavelength order and matches the laser spot formed by the semiconductor laser 100 at the light-emitting surface 203, the laser beam emitted by the semiconductor laser 100 can be focused. Since the size of the lens 201 matches the effective diameter of the laser spot formed by the semiconductor laser 100 at the light-emitting surface 203... The matching ensures that the entire light spot enters the aperture of the lens 201 without energy loss. This not only improves the purity of the output beam but also focuses the beam into a small, high-energy-density spot, thereby enhancing the coupling efficiency between this spot and downstream optical devices or optical fibers of the semiconductor laser module, and improving the overall performance of the semiconductor laser module. Simultaneously, because the size of the lens 201 is on the subwavelength order, stray light reflected back cannot enter the optical element 200, further suppressing stray light effects in the semiconductor laser module and improving its performance. The subwavelength size of the lens 201 also effectively suppresses diffraction effects, further reducing the beam divergence angle and enhancing the symmetry and stability of the far-field spot, providing higher-quality input conditions for subsequent beam shaping, beam combining, or fiber coupling.

[0066] In one embodiment, a photonic crystal structure is formed on the tapered outer surface of the optical element 200. See also... Figure 3 and Figure 4 , Figure 3 This is a schematic diagram of the structure of a semiconductor laser module provided in one embodiment of this application. In this figure, the film layer on the conical outer surface of the optical element 200 is disposed along the second direction. Figure 4 This is a schematic diagram of the structure of a semiconductor laser module provided in another embodiment of this application. In this figure, the film layer on the conical outer surface of the optical element 200 is disposed along the first direction.

[0067] The photonic crystal structure may include a one-dimensional photonic crystal structure, a two-dimensional photonic crystal structure, or a three-dimensional photonic crystal structure, and the morphologies of the one-dimensional photonic crystal structure, the two-dimensional photonic crystal structure, and the three-dimensional photonic crystal structure are different.

[0068] If it is a one-dimensional photonic crystal structure, then the one-dimensional photonic crystal structure is a stacked structure, which is formed by alternating stacking of two medium materials with different refractive indices on the conical outer surface of the optical element 200 in a direction perpendicular to the outer surface of the conical shape. For example, the medium material pair is silicon dioxide and tantalum pentoxide, or silicon nitride and silicon dioxide. The fabrication process of the one-dimensional photonic crystal structure is the simplest. It is formed by physical vapor deposition or atomic layer deposition on the conical outer surface of the optical element 200. In a preferred embodiment, 6 pairs of 12 layers of the one-dimensional photonic crystal structure are deposited on the conical outer surface of the optical element 200. The one-dimensional photonic crystal structure is formed by stacking two medium materials with different refractive indices. The optical thickness of the high and low refractive index layers is set to one-quarter of the wavelength of the emitted laser from the semiconductor laser 100, thereby forming a photonic bandgap at the target wavelength and producing extremely high reflectivity for normally incident light and light incident within a specific angle range.

[0069] If it is a two-dimensional photonic crystal structure, then the two-dimensional photonic crystal structure is an array structure, and the array structure is etched and formed on the outer surface of the cone. The surface of the array structure is uneven. The two-dimensional photonic crystal structure is etched and formed in the substrate material of the outer surface of the cone of the optical element 200. The shape of the two-dimensional photonic crystal structure is not limited; it can be a periodically arranged array of air holes or an array of dielectric pillars. The cross-section of the etched holes or pillars can be circular, square, or hexagonal, and its lattice arrangement can be a triangular lattice or a square lattice. The lattice constant α satisfies... Where λ is the laser wavelength, and n eff To achieve an effective refractive index, the position and width of the photonic bandgap can be adjusted by changing the radius of the aperture or the size of the cylinder, thereby suppressing incident light of a specific wavelength and angle. Furthermore, point defects or line defects can be introduced into the two-dimensional photonic crystal structure to form a micro-resonant cavity or waveguide. In this case, the side surface of the optical element 200 can not only passively suppress stray light but also actively modulate light, actively coupling stray light of a specific wavelength into the defects for collection or utilization. The two-dimensional photonic crystal structure can be patterned on the conical outer surface of the optical element 200 using electron beam lithography or nanoimprint lithography, and then transferred to the substrate material through an etching process.

[0070] If a three-dimensional photonic crystal structure is used, it is a material with a three-dimensional periodic refractive index change prepared on the conical outer surface of the optical element 200. For example, this structure can be based on a self-assembled opal structure or its inverse structure, which can generate photonic band gaps in all directions, thereby suppressing stray light incident at any angle. In use, a one-dimensional, two-dimensional, or three-dimensional photonic crystal structure can be arbitrarily selected as needed to reduce costs while ensuring stray light suppression.

[0071] In this embodiment, by setting a photonic crystal structure on the outer wall of the conical optical element 200, the suppression effect on stray light can be further improved. One-dimensional photonic crystal structures are suitable for suppressing stray light of a single operating wavelength, with energy processed in the form of reflection to avoid heat generation. Two-dimensional photonic crystal structures can achieve different responses to transverse electric and transverse magnetic modes and provide in-plane photonic bandgap, resulting in a wider suppression angle. Three-dimensional photonic crystal structures can generate omnidirectional photonic bandgap, and when combined with the conical optical element 200, can suppress stray light incident at any polar angle within a 360° azimuth angle, achieving the most comprehensive stray light suppression. This photonic bandgap-based suppression method, compared to traditional absorption or diffuse reflection, has the advantages of good spectral selectivity, high suppression efficiency, and low thermal effect.

[0072] In one embodiment, the photonic crystal structure is a microlens structure formed by an etching method. Specifically, the photonic crystal structure is a composite optical surface combining microlens and photonic crystal principles. Its surface morphology is an array of microlenses with macroscopic curvature. Each microlens has an aperture between 1 micrometer and 50 micrometers and a convex spherical or aspherical profile. Furthermore, on the surface of each microlens, periodically arranged subwavelength structural units are further fabricated through an etching process, thereby forming a metalens or photonic crystal lens. The microlens structure is achieved through a two-step etching process: first, the desired microlens surface morphology is formed on the side surface of the optical element 200 using photolithography or thermal reflow technology; second, a nanostructure pattern of the photonic crystal is defined on the formed microlens surface using electron beam lithography or nanoimprint lithography, and this pattern is transferred to the microlens material through reactive ion etching. The microlens structure serves two purposes: first, due to its macroscopic curved surface morphology, it can deflect or diverge stray light, changing its propagation direction; second, due to the photonic crystal nanostructure on its surface, it can generate a photonic bandgap effect for light of specific wavelengths; ultimately achieving omnidirectional suppression of stray light and improving the performance and reliability of the semiconductor laser module.

[0073] In one embodiment, the film layer consists of two layers, formed by stacking a first film layer material and a second film layer material. Both the first and second film layer materials are selected from tantalum pentoxide, silicon dioxide, titanium dioxide, hafnium dioxide, aluminum oxide, or silicon nitride, and the first and second film layer materials are different. Tantalum pentoxide has a refractive index of 2.1-2.3, and silicon dioxide has a refractive index of 1.45. Both materials possess high optical transparency, low absorption loss, and high chemical stability. Furthermore, the tantalum pentoxide / silicon dioxide dielectric film pair has a high laser damage threshold, capable of withstanding long-term irradiation by high-power lasers without significant damage. Using these two materials allows for the formation of a high-low refractive index pair, suitable for forming interference reflection structures. Silicon nitride, on the other hand, has high strength, making it suitable for forming robust film layers. Of course, other materials can also be selected to form high-low refractive index pairs, such as titanium dioxide with a refractive index of 2.2, hafnium dioxide with a refractive index of 1.9, and aluminum oxide with a refractive index of 1.65. Any of these materials can be selected to form high-low refractive index pairs, ultimately forming the complete film layer.

[0074] Specifically, the refractive index of the film layer varies radially along the outer surface of the cone. The film layer has a first refractive index in the central region of the outer surface of the cone, and the refractive index of the film layer continuously decreases from the central region outwards. The doping concentrations of the two materials in the film layer vary radially to achieve a continuous change in the refractive index. The film layer is formed from a first film layer material and a second film layer material. In one embodiment, the first film layer material is a high-refractive-index material, and the second film layer material is a low-refractive-index material. In the central region of the outer surface of the cone, the volume doping concentration of the first film layer material is the highest, resulting in the highest refractive index in this region. The first film layer material and the second film layer material are alternately formed radially outwards from the outer surface of the cone, and the doping concentration of the first film layer material continuously decreases gradient while the doping concentration of the second film layer material continuously increases gradient, ultimately forming the complete film layer. In this embodiment, the refractive index of the film layer decreases continuously from the center outward. When stray light is incident on the film layer, its propagation path is guided and absorbed by the film layer according to Fresnel's law, which reduces the risk of stray light incident on the light-emitting cavity surface 101 of the semiconductor laser 100, thereby improving the overall reliability and lifespan of the semiconductor laser module.

[0075] In one embodiment, the light-incident surface 202 of the optical element 200 is coated with an antireflection film. The antireflection film is a multilayer dielectric film structure, preferably comprising alternating stacks of silicon dioxide and tantalum pentoxide. The film thickness is designed according to the laser operating wavelength, ensuring the optical thickness meets the quarter-wavelength condition to achieve minimum reflectivity within a specific incident angle range. This antireflection film is deposited using physical vapor deposition or plasma-enhanced chemical vapor deposition processes, ensuring a dense, uniform film layer and a strong and reliable bond with the light-incident surface 202 of the optical element 200. The design of the antireflection film matches the shape of the light-incident surface 202 of the optical element 200, avoiding performance degradation of the semiconductor laser module due to angular deviations.

[0076] In this embodiment, by providing an antireflection film at the light-incident surface 202 of the optical element 200, Fresnel reflection at the light-incident surface 202 can be suppressed, reducing reflection loss. At the same time, the low reflectivity of the light-incident surface 202 can reduce the backlight returning from the inside of the optical element 200 to the cavity surface of the semiconductor laser 100, avoiding interference with the laser mode, frequency jumps, or noise.

[0077] In one embodiment, the light-emitting cavity surface 101 of the semiconductor laser 100 is in contact with the light-incident surface 202 of the optical element 200, or there is a gap between the light-emitting cavity surface 101 of the semiconductor laser 100 and the light-incident surface 202 of the optical element 200; wherein the light-incident surface 202 of the optical element 200 is coated with a thermally conductive material, or the light-emitting cavity surface 101 of the semiconductor laser 100 is coated with a thermally conductive material. The thermally conductive material is a high thermal conductivity dielectric thin film, such as aluminum nitride, beryllium oxide, or silicon nitride, and the thickness of this thermally conductive film layer satisfies the half-wavelength condition, thereby ensuring that light of the corresponding wavelength can be fully transmitted. This thermally conductive material is formed by physical vapor deposition or chemical vapor deposition processes, ensuring that the film layer is continuous, dense, and tightly bonded to the light-emitting cavity surface 101 of the semiconductor laser 100 or the light-incident surface 202 of the optical element 200. The thermally conductive film layer can be in direct physical contact with the light-emitting cavity surface 101 of the semiconductor laser 100 or the light-incident surface 202 of the optical element 200, or it can achieve optical contact by filling with thermally conductive adhesive to eliminate air gaps and reduce interface thermal resistance. If there is a gap between the light-emitting cavity surface 101 of the semiconductor laser 100 and the light-incident surface 202 of the optical element 200, the width of the gap ranges from 10 micrometers to 500 micrometers, preferably from 50 micrometers to 200 micrometers. This gap can be a vacuum environment or filled with inert gas or dry air to avoid oxidation or contamination of the optical surface. The gap can act as a thermal buffer layer, reducing the heat generated by the semiconductor laser 100 during operation and its conduction to the optical element 200, reducing the impact on beam quality, and thus improving the performance of the semiconductor laser module.

[0078] Furthermore, in practical applications, to ensure the adaptability of the semiconductor laser module under different environmental conditions, the thermally conductive material of the light-incident surface 202 of the optical element 200 can be surface-treated or have a functional coating added. For example, its thermal conductivity can be enhanced by doping with specific nanoparticles, or a protective film that resists corrosion and oxidation can be applied to its surface to extend its service life and improve reliability.

[0079] In this embodiment, by coating the light-emitting cavity surface 101 of the semiconductor laser 100 or the light-incident surface 202 of the optical element 200 with a thermally conductive material, a low thermal resistance channel can be formed between the semiconductor laser 100 and the optical element 200. This allows for the rapid dissipation of heat generated on the light-emitting cavity surface 101 when the semiconductor laser 100 is operating, preventing wavelength drift, output power reduction, or cavity surface damage caused by heat accumulation in the semiconductor laser 100. This improves the operating life and reliability of the semiconductor laser 100. Furthermore, it ensures that the beam transmission from the semiconductor laser 100 to the optical element 200 is unaffected by thermal disturbances, maintaining a stable output beam shape and enhancing the overall performance of the semiconductor laser module.

[0080] It is understandable that in practical applications, the optical element 200 and the lens 201 with a size on the subwavelength order are placed in the same semiconductor laser module, and a film with a changing refractive index and a photonic crystal structure are formed on the conical outer surface of the optical element 200. At the same time, an anti-reflection coating is deposited on the light-incident surface 202 of the optical element 200. Such a setup can not only achieve omnidirectional stray light suppression, but also improve the stability and energy utilization of laser beam transmission, thereby improving the overall stability and reliability of the semiconductor laser module.

[0081] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0082] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A semiconductor laser module, characterized in that, include: A semiconductor laser (100) includes a light-emitting cavity surface (101). A reflector (300) has a light incident end face (301); An optical element (200) is disposed between the light-emitting cavity surface (101) and the light-incident end surface (301) for guiding the light emitted from the semiconductor laser (100) to the light-incident end surface (301). The optical element (200) has an incident surface (202) opposite to the light-emitting cavity surface (101), an exit surface (203) opposite to the light-incident end surface (301), and a conical outer surface. The outer surface of the cone is coated with a film layer whose refractive index varies along a first direction or a second direction. The first direction is the extension direction from the light-incident surface (202) to the light-exit surface (203), and the second direction is perpendicular to the first direction. The film is made of two materials, and the total thickness of the film is inversely proportional to the difference in refractive index between the two materials. The refractive index of the film varies along the radial direction of the outer surface of the cone. The film has a first refractive index in the central region of the outer surface of the cone, and the refractive index of the film continuously decreases from the central region outward. The outer diameter of the optical element (200) gradually decreases along the direction from the light-incident surface (202) to the light-exit surface (203).

2. The semiconductor laser module according to claim 1, characterized in that, The optical element (200) has a lens (201) on its light-emitting surface (203), and the size of the lens (201) is on the subwavelength order. The effective diameter of the lens (201) matches the effective diameter of the laser spot formed by the semiconductor laser (100) at the position of the light-emitting surface (203).

3. The semiconductor laser module according to claim 2, characterized in that, The lens (201) includes a hemispherical, aspherical, or diffractive optical surface.

4. The semiconductor laser module according to claim 2, characterized in that, When the lens (201) is a hemispherical or aspherical surface, the hemispherical or aspherical surface protrudes from the light-incident surface (202) in the direction of extending towards the light-outceasing surface (203); When the lens (201) is a diffractive optical surface, the diffractive optical surface is a periodic or non-periodic microstructure.

5. The semiconductor laser module according to claim 1, characterized in that, The outer conical surface of the optical element (200) is formed with a photonic crystal structure, which includes a one-dimensional photonic crystal structure, a two-dimensional photonic crystal structure or a three-dimensional photonic crystal structure, and the morphology of the one-dimensional photonic crystal structure, the two-dimensional photonic crystal structure and the three-dimensional photonic crystal structure are different.

6. The semiconductor laser module according to claim 5, characterized in that, The photonic crystal structure includes a one-dimensional photonic crystal structure, which is a stacked structure. The stacked structure is formed by alternately stacking two media materials with different refractive indices on the conical outer surface of the optical element (200) in a direction perpendicular to the outer surface of the conical surface; or... The photonic crystal structure includes a two-dimensional photonic crystal structure, which is an array structure. The array structure is etched onto the outer surface of the cone, and the surface of the array structure is uneven. The photonic crystal structure includes a three-dimensional photonic crystal structure, which is a material with a three-dimensional periodic refractive index change prepared on the conical outer surface of the optical element (200).

7. The semiconductor laser module according to claim 1, characterized in that, The film layer consists of two layers, formed by stacking a first film layer material and a second film layer material. Both the first film layer material and the second film layer material are one of tantalum pentoxide, silicon dioxide, titanium dioxide, hafnium dioxide, aluminum oxide, or silicon nitride, and the first film layer material and the second film layer material are different.

8. The semiconductor laser module according to claim 1, characterized in that, The doping concentrations of the two materials in the film layer vary along a radial gradient to achieve a continuous change in the refractive index of the film layer.

9. The semiconductor laser module according to claim 1, characterized in that, The light-emitting cavity surface (101) of the semiconductor laser (100) is in contact with the light-incident surface (202) of the optical element (200), or there is a gap between the light-emitting cavity surface (101) of the semiconductor laser (100) and the light-incident surface (202) of the optical element (200). The light-incident surface (202) of the optical element (200) is coated with a thermally conductive material, or the light-exiting cavity surface (101) of the semiconductor laser (100) is coated with a thermally conductive material.

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