Semiconductor laser side-pumped system and method of manufacturing the same

Abstract

The application provides a semiconductor laser side-pumping system and a preparation method thereof, and relates to the technical field of lasers.The system comprises a crystal rod and multiple groups of laser modules.Each group of laser modules comprises a light-emitting structure, a homogenizing component, a first modulation device and a second modulation device.The light-emitting structure is used for emitting an initial light beam towards the homogenizing component.The homogenizing component is used for shaping the initial light beam into a quasi-flat-top light beam and emitting the quasi-flat-top light beam to the first modulation device.The first modulation device is used for shaping the quasi-flat-top light beam into a bowl-shaped light beam in a form of attenuation, so that the middle attenuation rate is higher than the edge attenuation rate.The bowl-shaped light beam is emitted into the crystal rod from one side of the crystal rod.The bowl-shaped light beam that has passed through the crystal rod is emitted from the opposite side of the crystal rod and towards the second modulation device.According to the optical properties of the crystal rod, the second modulation device is configured to shape the bowl-shaped light beam into an incident light in a form of reflection, so that the middle reflection rate is lower than the edge reflection rate, and emit the incident light to the crystal rod.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a side-pumping system for a semiconductor laser and its fabrication method. Background Technology

[0002] Solid-state lasers have wide applications in industrial processing, medical surgery, and scientific research. Among them, 1064nm wavelength solid-state lasers are highly favored due to their excellent beam quality and stable output characteristics. In current technology, an 808nm wavelength semiconductor laser is often used as a side-pump source, with ND:YAG crystal as the laser gain medium, to achieve 1064nm laser output through an optical-to-optical conversion process. The fluorescence uniformity of the crystal inside the pump source is one of the key factors affecting laser performance. It not only directly determines the beam quality of the output laser but is also closely related to the stability and reliability of the system.

[0003] In existing technologies, the design of side-pumping structures primarily revolves around improving fluorescence uniformity. In low-power applications, single-dimensional or low-dimensional pumping structures are usually sufficient. However, as output power increases, higher-dimensional pumping structures, such as 7-dimensional or 13-dimensional pumps, are necessary to maintain adequate fluorescence uniformity. While these multi-dimensional pumping structures can improve fluorescence distribution uniformity to some extent, they also significantly increase system complexity. Multi-dimensional pumping not only requires more pump sources and more precise optical alignment systems but also leads to a sharp increase in heat dissipation pressure. Under high-power operation, even slight deviations in fluorescence uniformity can cause uneven thermal stress distribution within the crystal, potentially leading to serious problems such as crystal fragmentation. Summary of the Invention

[0004] The purpose of this invention is to provide a side-pumping system for a semiconductor laser and its fabrication method, which alleviates the problem of achieving uniform fluorescence distribution through complex structures in existing side-pumping systems for semiconductor lasers and solves the technical problem of increased heat dissipation burden of the system.

[0005] In a first aspect, the present invention provides a semiconductor laser side-pumping system, comprising: a crystal rod and multiple sets of laser modules, wherein the multiple sets of laser modules are arranged circumferentially around the outer side of the crystal rod.

[0006] Each laser module includes a light-emitting structure, a homogenizing component, a first modulator, and a second modulator. The light-emitting structure, homogenizing component, and first modulator are all located on one side of the crystal rod, and the second modulator is located on the opposite side of the crystal rod. The light-emitting structure, homogenizing component, and first modulator are arranged sequentially from the center of the crystal rod to the direction away from the center of the crystal rod.

[0007] The light-emitting structure is used to emit an initial beam of light toward the homogenizing component;

[0008] The homogenization component is used to shape the initial beam into a flat-top beam and output it to the first modulation device;

[0009] The first modulation device is used to shape the flat-top beam so that the flat-top beam is shaped into a bowl-shaped beam with a higher attenuation rate in the middle than attenuation rate at the edge. The bowl-shaped beam enters the crystal rod from one side.

[0010] The bowl-shaped beam that passes through the crystal rod exits from the opposite side of the crystal rod and is directed toward the second modulation device;

[0011] Based on the optical properties of the crystal rod, the second modulation device is configured to shape the bowl-shaped beam into incident light with a reflectivity in the middle that is lower than that at the edges, and then output it to the crystal rod.

[0012] Furthermore, the first modulation device includes a light-transmitting film with gradually varying transmittance, located between the homogenizing component and the crystal rod, with the transmittance of the light-transmitting film gradually increasing from the center to the edge.

[0013] Furthermore, the transmittance of the light-transmitting film ranges from 0.84 to 1.

[0014] Furthermore, the second modulation device includes a polarizing film layer, the reflective surface of which is curved, and the polarizing film layer and the first modulation device are located on opposite sides of the crystal rod in the radial direction.

[0015] The polarizing film is used to reflect the S-beam in the bowl-shaped beam. The reflectivity of the polarizing film gradually increases from the center to the edge.

[0016] Furthermore, the reflectivity of the polarizing film ranges from 0.88 to 1.

[0017] Furthermore, the second modulation device includes an annular light-transmitting tube, which is located on the circumferential outer side of the crystal rod and on the inner side of the plurality of first modulation devices that are coiled in an annular shape.

[0018] Multiple polarizing film layers are attached to the tube wall on the side of the annular light-transmitting tube facing the crystal rod.

[0019] Furthermore, the homogenization component is located between the light-emitting structure and the first modulation device. The homogenization component includes a light-incident surface and a light-emitting surface, with the light-incident surface facing the light-emitting structure and the light-emitting surface facing the first modulation device.

[0020] The light-emitting surface includes a curved portion, which is arranged along the fast axis direction of the quasi-flat-top beam and is recessed towards the light-emitting surface.

[0021] High-reflectivity films are provided on both sides of the homogenizing component located in the fast axis direction of the quasi-flat-top beam; the distance between the two sides of the homogenizing component located in the fast axis direction of the quasi-flat-top beam gradually decreases from the incident surface to the exit surface.

[0022] Furthermore, the radius of curvature of the curved surface ranges from 4mm to 20mm;

[0023] And / or, the vertical distance between the most concave position of the curved part and the light-emitting surface ranges from 4 to 10 mm.

[0024] Furthermore, the light-emitting structure includes multiple light-emitting units spaced apart, with the spacing between two adjacent light-emitting units ranging from 0.7mm to 1.2mm.

[0025] And / or, the range of the fast axis divergence angle of the light-emitting unit is 50°-60°;

[0026] And / or, the number of light-emitting points in the light-emitting unit ranges from 19 to 63 points;

[0027] And / or, the diameter of the crystal rod ranges from 10mm to 20mm;

[0028] And / or, the doping concentration of the crystal rod ranges from 0.4 at% to 1 at%

[0029] And / or, the optical properties of the crystal rod include at least one of refractive index, doping concentration, and diameter;

[0030] And / or, the number of laser modules is three or five;

[0031] And / or, a heat dissipation structure is provided between the second modulation device and the crystal rod.

[0032] Secondly, the present invention provides a method for fabricating a semiconductor laser side-pumping system, used to fabricate the aforementioned semiconductor laser side-pumping system, comprising the following steps:

[0033] Based on the light intensity distribution of the initial beam, the optical properties of the homogenizing component, and the desired fluorescence distribution of the crystal rod, the decay form of the gradient transmittance of the first modulation device and the reflection form of the reflectance of the second modulation device are obtained.

[0034] The first modulation device and the second modulation device are prepared according to the decay mode and the reflection mode.

[0035] Furthermore, the decay form of the gradient transmittance of the first modulator is represented by the function T(x,y); the reflection form of the reflectance of the second modulator is represented by the function SP(x,y).

[0036] According to the following formula:

[0037] F S(x,y)=Q1;

[0038] T(x,y) Q1 = Q2;

[0039] YAG Q2 SP(x,y) = Q3;

[0040] Obtain functions T(x,y) and SP(x,y); where S(x,y) is the light intensity distribution matrix of the initial beam, Q1 is the light intensity distribution matrix of the flat-top beam, F is the expression of the optical properties of the homogenizing component, Q2 is the light intensity distribution matrix of the bowl-shaped beam, YAG is the expression of the optical properties of the crystal rod, and Q3 is the desired fluorescence distribution matrix. S(x,y), F, and YAG are known, and Q3 is a set value.

[0041] Furthermore, the homogenization component is located between the light-emitting structure and the first modulation device. The homogenization component includes an incident surface and an exit surface. The exit surface includes a curved portion. In the radial direction of the crystal rod, the distance between the most concave position of the incident surface and the exit surface is L. The radius of curvature of the incident surface is r. The angle between the sidewall of the homogenization component located in the fast axis direction of the quasi-flat-top beam and the cross-section of the crystal rod is a. Then, the expression for the optical properties of the homogenization component is F(L,r,a).

[0042] And / or, if the diameter of the crystal rod is D, the doping concentration is c, the refractive index is n, and the surface scattering follows a simplified Lambertian scattering model, i.e. SL, then the expression for the optical properties of the crystal rod is YAG(D,c,n,SL).

[0043] And / or, suppose the light intensity distribution of the initial beam is represented as the set of light intensities of k discrete light points in a two-dimensional coordinate system, and set the root mean square error (RMS) of the light intensities of the k light points in Q3 to be less than a set amount, so as to fit and obtain Q3.

[0044] This invention has at least the following advantages or beneficial effects:

[0045] The present invention provides a semiconductor laser side-pumping system, comprising: a crystal rod and multiple sets of laser modules, wherein the multiple sets of laser modules are arranged circumferentially around the outer side of the crystal rod; each set of laser modules includes a light-emitting structure, a homogenizing component, a first modulator, and a second modulator, wherein the light-emitting structure, the homogenizing component, and the first modulator are all located on one side of the crystal rod, and the second modulator is located on the opposite side of the crystal rod, and the light-emitting structure, the homogenizing component, and the first modulator are arranged sequentially from near the center of the crystal rod to away from the center of the crystal rod; the light-emitting structure is used to emit an initial light towards the homogenizing component. A beam; a homogenization component is used to shape the initial beam into a near-flat-top beam and output it to a first modulator; the first modulator is used to shape the near-flat-top beam so that the near-flat-top beam is shaped into a bowl-shaped beam with a higher attenuation rate in the middle than attenuation rate at the edges, and the bowl-shaped beam enters the crystal rod from one side; the bowl-shaped beam that passes through the crystal rod exits from the opposite side of the crystal rod and is directed towards a second modulator; according to the optical properties of the crystal rod, the second modulator is configured to shape the bowl-shaped beam into incident light with a lower reflectivity in the middle than at the edges and output it to the crystal rod.

[0046] After passing through the homogenization component, the light beam becomes a near-flat-top beam, with reduced intensity in the central region and improved beam uniformity. However, the near-flat-top beam still exhibits a super-Gaussian distribution, with the intensity at the center remaining stronger than at the edges. Therefore, it cannot directly affect the crystal rod and needs to pass through a first modulation device to further reduce the intensity in the central region. This first modulation device reshapes the near-flat-top beam into a bowl-shaped beam with a higher attenuation rate in the center than at the edges. The intensity in the center of the bowl-shaped beam is lower than that at the edges. When the bowl-shaped beam first enters the crystal rod, some light is absorbed. Initially, the outer edges of the crystal rod absorb the most light. As the partially absorbed beam continues to penetrate the crystal rod, it experiences scattering and heat loss along its path from the surface to the center, resulting in relatively low absorbable light energy at the center. Assuming multiple stacked beams are Gaussian or super-Gaussian beams, which are inherently strong at the center, this strong central region will overlap at the center of the crystal rod, resulting in even stronger light intensity at the center. However, when a bowl-shaped beam, with its lower intensity distribution at the center, enters the crystal rod, more light is absorbed at the periphery than at the center, significantly reducing the strong center phenomenon. A portion of the beam after passing through the crystal rod is then directed to a second modulator, which reshapes the beam, making the reflected light back to the crystal rod even weaker at the center, further reducing the intensity at the center and preventing the strong center problem. This improves fluorescence uniformity. Furthermore, because reflection alters the optical path, the beam does not return along the same route, further increasing fluorescence uniformity within the crystal rod. This structure achieves fluorescence uniformity within the crystal rod without requiring numerous laser modules or a thick crystal rod, simplifying the structure and significantly reducing the system's heat dissipation burden. Attached Figure Description

[0047] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0048] Figure 1 A top view of a semiconductor laser side-pumping system provided in an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of the homogenization component of a semiconductor laser side-pumping system provided in an embodiment of the present invention;

[0050] Figure 3The optical path along the fast axis of the homogenization component of the semiconductor laser side-pumping system provided in this embodiment of the invention;

[0051] Figure 4 The light spot resembles a flat-top beam;

[0052] Figure 5 The gradient transmittance curve of the first modulation device of the semiconductor laser side-pumping system provided in the embodiments of the present invention;

[0053] Figure 6 The light spot is a bowl-shaped beam;

[0054] Figure 7 The intensity distribution of the bowl-shaped beam;

[0055] Figure 8 A schematic diagram of the annular light-transmitting tube of the semiconductor laser side-pumping system provided in an embodiment of the present invention;

[0056] Figure 9 The gradient reflectivity curve of the polarization film layer of the semiconductor laser side-pumping system provided in the embodiments of the present invention;

[0057] Figure 10 Fluorescence distribution of a crystal rod in a semiconductor laser side-pumping system provided in an embodiment of the present invention;

[0058] Figure 11 Fluorescence distribution curve of a crystal rod in a semiconductor laser side-pumping system provided in an embodiment of the present invention.

[0059] Icons: 1-Light-emitting structure; 2-Homogeneous component; 21-Light-incident surface; 22-Light-emitting surface; 3-First modulation device; 4-Polarizing film layer; 5-Annular light-transmitting tube; 6-Heat dissipation structure; 7-High reflectivity film; 8-Crystal rod; 9-Light-transmitting film; 10-Second modulation device; 11-Glass substrate. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0061] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0062] 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.

[0063] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or component 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 of this invention. 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.

[0064] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0065] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0066] The fluorescence uniformity within the effective aperture of the semiconductor laser side-pumping system provided by this invention can reach over 95%.

[0067] like Figure 1 As shown, the system includes a crystal rod 8 and multiple sets of laser modules, which are arranged circumferentially around the outer edge of the crystal rod 8. In this embodiment, the crystal rod 8 is located at the center, and there are three sets of laser modules on the periphery, arranged at 120° angles between each pair of laser modules circumferentially. In other feasible solutions, the number of laser modules can also be five. By using a smaller number of laser modules, a low-dimensional side-pumped system with high fluorescence uniformity can be achieved, with fluorescence uniformity within the effective aperture reaching over 95%. Figure 10 and Figure 11As shown. In the prior art, at least 7 sets of laser modules are required in conjunction with a relatively thick crystal rod 8 to achieve high pump power and meet the requirements of large spot size. However, in this embodiment, at least three sets of laser modules can be achieved, which greatly reduces production costs and heat dissipation pressure.

[0068] like Figure 1 and Figure 8 As shown, each group of laser modules is configured in the same way, with... Figure 1 The structure of the leftmost group of laser modules will be explained using this example. Each group of laser modules includes a light-emitting structure 1, a homogenizing component 2, a first modulator 3, and a second modulator 10. The light-emitting structure 1, homogenizing component 2, and first modulator 3 are all located on one side of the crystal rod 8, i.e., the left side of the crystal rod 8. The second modulator 10 is located on the opposite side of the crystal rod 8, i.e., the right side of the crystal rod 8. The light-emitting structure 1, homogenizing component 2, and first modulator 3 are arranged sequentially from near the center of the crystal rod 8 to away from the center of the crystal rod 8.

[0069] like Figure 1 and Figure 8 As shown, the light emitted by the light-emitting structure 1 passes through the homogenization component 2, the first modulation device 3, the crystal rod 8, and the second modulation device 10 before returning to the crystal rod 8. When the bowl-shaped beam enters the crystal rod 8 for the first time, a portion of the light is absorbed. Initially, the outer periphery of the crystal rod 8 absorbs the most light. As the partially absorbed beam continues to penetrate the crystal rod 8, it experiences scattering and heat loss along its path from the surface to the center, resulting in lower absorbable light energy at the center of the crystal rod 8. A portion of the beam after passing through the crystal rod 8 then strikes the second modulation device 10, which reshapes the beam, further reducing the intensity at the center of the crystal rod 8 and preventing a strong center problem. This improves fluorescence uniformity. Furthermore, because reflection alters the light path, the beam does not return along the same route, further enhancing the fluorescence uniformity within the crystal rod 8.

[0070] Specifically, the light-emitting structure 1 emits an initial beam toward the homogenizing component 2, which can be a Gaussian beam. The homogenizing component 2 shapes the initial beam into a near-flat-top beam and outputs it to the first modulator 3. The first modulator 3 shapes the near-flat-top beam so that it is shaped into a bowl-shaped beam with a higher attenuation rate in the middle than at the edges. The bowl-shaped beam has an intensity distribution in a specified direction where the intensity in the middle region is lower than that at the edges, and the intensity drops sharply at the edges. Figure 6 and Figure 7 As shown.

[0071] A bowl-shaped light beam enters the crystal rod 8 from the left side, passes through the crystal rod 8, and exits from the opposite side, i.e., the right side, and then directs towards the second modulator 10. To achieve uniform fluorescence in the crystal rod 8, the reflectivity of the second modulator 10 is configured to be related to the optical properties of the crystal rod 8. Therefore, based on the optical properties of the crystal rod 8, the second modulator 10 is configured to shape the bowl-shaped light beam into incident light with a reflectivity lower in the center than at the edges, and then output it to the crystal rod 8.

[0072] After passing through homogenization component 2, the light beam becomes a near-flat-top beam, with reduced intensity in the central region and improved beam uniformity. However, the near-flat-top beam still exhibits a super-Gaussian distribution, with the intensity at the center remaining stronger than at the edges. Therefore, it cannot directly act on the crystal rod 8 and needs to pass through the first modulation device 3 to further reduce the intensity in the central region, thus forming a bowl-shaped beam. The intensity in the center of the bowl-shaped beam is lower than that at the edges. When the bowl-shaped beam first enters the crystal rod 8, a portion of the light is absorbed. Initially, the outer edges of the crystal rod 8 absorb the most light. As the partially absorbed beam continues to penetrate into the crystal rod 8, scattering and heat loss occur along the path from the surface to the center, resulting in relatively low absorbable light energy reaching the center of the crystal rod 8. Assuming multiple beams incident from a stacked array are Gaussian or super-Gaussian beams, which are inherently strong at the center, this strong central region will overlap at the center of crystal rod 8, resulting in even stronger light intensity at the center of crystal rod 8. However, when a bowl-shaped beam with a similar intensity distribution enters crystal rod 8, the intensity in the center of the bowl-shaped beam is lower than the intensity at the edges, leading to greater absorption at the periphery of crystal rod 8 and significantly less absorption at the center. This greatly avoids the phenomenon of a strong center at the center of crystal rod 8 during absorption. A portion of the beam after passing through crystal rod 8 is directed to the second modulation device 10, which then reshapes the outgoing beam, making the intensity of the beam reflected back to crystal rod 8 even lower at the center. This further reduces the intensity at the center of crystal rod 8, preventing the strong center problem and improving fluorescence uniformity. Furthermore, because reflection changes the optical path, the beam incident on crystal rod 8 does not return along the same path, thus further increasing the fluorescence uniformity within crystal rod 8.

[0073] The first modulation device 3 includes a light-transmitting film 9 with gradually varying transmittance. The light-transmitting film 9 is located between the homogenizing component 2 and the crystal rod 8. The transmittance of the light-transmitting film 9 gradually increases from the center to the edge.

[0074] Because the beam after passing through the homogenizing component 2 has a flat-top super-Gaussian distribution, the light intensity at the center is still stronger than that at the edge. Therefore, when the three-dimensional array is incident on the crystal rod 8, the crystal rod 8 still has a strong center after beam superposition. Therefore, the first modulation device 3 adopts a transmittance gradient modulation form. The light-transmitting film 9 can be deposited on the glass substrate 11 (thickness range can be 1 mm - 2 mm). The glass substrate 11 is placed between the homogenizing component 2 and the annular light-transmitting tube 5. The glass substrate 11 can be glued to the light-emitting surface 22 of the homogenizing component 2. The length and width dimensions of the glass substrate 11 match the light-emitting surface 22 of the homogenizing component 2. The transmittance of the light-transmitting film 9 is not uniform at various positions and is set in a gradient. Furthermore, the transmittance of the light-transmitting film 9 gradually increases from the center to the edge.

[0075] Since the fluorescence distribution inside crystal rod 8 is determined by a combination of factors, including scattering loss inside and on the surface of the crystal, internal doping uniformity, and incident light intensity distribution, software can be used to collect a large amount of data to automatically fit a relatively close transmittance gradient curve, such as... Figure 4 As shown, the attenuation rate is higher in the middle and lower on both sides, with the maximum intensity loss rate at the center being approximately 15%. After the beam passes through homogenization component 2 and then through the first modulation device 3, the flat-top beam transforms into a bowl-shaped beam. The intensity distribution and curve of the bowl-shaped beam are illustrated in the diagram below. Figure 5 As shown. This type of light intensity distribution can greatly avoid the phenomenon of a strong center appearing at the center of the crystal rod 8 during absorption.

[0076] The transmittance of the light-transmitting film 9 can range from 0.84 to 1.

[0077] The second modulation device 10 includes a polarizing film layer 4, the reflecting surface of which is curved. The polarizing film layer 4 and the first modulation device 3 are located on opposite sides of the crystal rod 8 in the radial direction. The polarizing film layer 4 is used to reflect the S-beam in the bowl-shaped beam. From the center to the edge of the polarizing film layer 4, the reflectivity of the polarizing film layer 4 gradually increases, such as... Figure 9 As shown.

[0078] The reflectivity of polarizing film layer 4 ranges from 0.88 to 1.

[0079] The semiconductor laser side-pumping system includes an annular light-transmitting tube 5, which has an inner diameter of 6-8 mm and an outer diameter of 7-9 mm. The annular light-transmitting tube 5 is located on the circumferential outer side of the crystal rod 8 and inside the plurality of first modulation devices 3 coiled in a ring. Multiple polarization film layers 4 are attached to the tube wall of the annular light-transmitting tube 5 on the side facing the crystal rod 8.

[0080] Multiple polarizing film layers 4 are fixed using the same annular light-transmitting tube 5, which facilitates the fixation of the polarizing film layers 4. Furthermore, when the center of the annular light-transmitting tube 5 coincides with the center of the crystal rod 8, the multiple polarizing film layers 4 can be uniformly arranged circumferentially on the outer side of the crystal rod 8, resulting in higher uniformity of the three optical paths. The reflectance distribution curve of the polarizing film layer 4 is obtained by fitting using software, as shown below. Figure 7 As shown, the central part has low reflectivity, while the two sides have higher reflectivity, resulting in a light intensity loss of approximately 11% at the center to compensate for light intensity absorption at the edges of the crystal rod 8. The annular light-transmitting tube 5 is still made of fused silica glass.

[0081] The homogenizing component 2 is located between the light-emitting structure 1 and the first modulation device 3, and its material can be quartz. Preferably, it is a shaped quartz tube. The three homogenizing components 2 can be connected end to end along the circumference (e.g., by adhesive) to form a tubular integral structure.

[0082] like Figure 2 and Figure 3 As shown, the homogenization component 2 includes an incident light surface 21 and an exit light surface 22. The size of the incident light surface 21 can be 11mm×7mm. The incident light surface 21 faces the light-emitting structure 1, and the distance between the two can be 1mm-5mm. The exit light surface 22 faces the first modulation device 3. The exit light surface 22 includes a curved part for receiving the light beam. The curved part is arranged along the fast axis direction of the quasi-flat-top beam and is recessed towards the exit light surface 22. The radius of curvature can be 4mm-20mm.

[0083] High-reflectivity films 7 are provided on both side walls of the homogenizing component 2 along the fast axis of the near-flat-top beam to prevent light leakage. From the incident surface 21 towards the emitting surface 22, the distance between the two side walls of the homogenizing component 2 along the fast axis of the near-flat-top beam gradually decreases. The emitting surface 22 can be 8mm × 6mm. The vertical distance between the most concave position of the curved surface and the emitting surface 22 ranges from 4 to 10mm. The light-emitting structure 1 includes multiple spaced-apart light-emitting units, which can be bars. The spacing between any two adjacent light-emitting units can be equal, ranging from 0.7mm to 1.2mm. Each individual light-emitting unit can have a fast-axis divergence angle of 50°-60° and a slow-axis divergence angle of 6°-12°. The number of light-emitting points can be 19-63, and the spacing between the light-emitting points can be 0.17-0.5mm. Their center wavelengths are all 808nm, which is S-polarized, with an S-polarization ratio of over 90%. The maximum single-unit power of light emission can reach 600W.

[0084] The diameter of crystal rod 8 ranges from 10 mm to 20 mm. The doping concentration of crystal rod 8 ranges from 0.4 at% to 1 at%. The optical properties of crystal rod 8 include at least one of refractive index, doping concentration, and diameter.

[0085] A heat dissipation structure 6 is provided between the second modulation device 10 and the crystal rod 8. The heat dissipation structure 6 may include a flow channel with a thickness of 2mm-4mm, and coolant flows through the flow channel.

[0086] In one embodiment, the laser device further includes the aforementioned semiconductor laser side-pumping system. The laser device also includes two opposing cavity mirrors forming a resonant cavity. The semiconductor laser side-pumping system is located within the resonant cavity. That is, the crystal rod 8 and multiple laser modules are positioned between the two cavity mirrors to form a stable, high-power, and highly uniform laser output.

[0087] The present invention provides a method for fabricating a semiconductor laser side-pumping system, used to fabricate the aforementioned semiconductor laser side-pumping system, comprising the following steps:

[0088] Based on the light intensity distribution of the initial beam, the optical properties of the homogenizing component 2, and the desired fluorescence distribution of the crystal rod 8, the decay form of the gradient transmittance of the first modulation device 3 and the reflection form of the reflectance of the second modulation device 10 are obtained.

[0089] The initial light beam passes sequentially through homogenization component 2, first modulation device 3, and second modulation device 10 before entering the crystal rod 8. The desired fluorescence distribution of the crystal rod 8 is influenced by homogenization component 2, first modulation device 3, second modulation device 10, and crystal rod 8, respectively. Therefore, when the intensity distribution of the initial light beam and the optical properties of homogenization component 2 are known, and the desired fluorescence distribution of crystal rod 8 is given, the decay form of the gradient transmittance of first modulation device 3 and the reflection form of reflection of second modulation device 10 can be calculated. Then, first modulation device 3 and second modulation device 10 are fabricated based on the decay and reflection forms.

[0090] When the light beam exits from the homogenization component 2, its light spot has a specific intensity distribution. To reduce the computational burden on the computer, k rays can be selected (in practice, k is equal to infinity). In this embodiment, k = 10000. At this time, each ray has a different intensity value. Let a matrix Q1 = The matrix includes the light intensity distribution of the light spot at this time. The Q1 matrix is ​​the correlation function of the homogenization component 2, and F is the expression of the optical properties of the homogenization component 2.

[0091] In the radial direction of the crystal rod 8, the distance between the most concave position of the incident surface 21 of the homogenizing component 2 and the exit surface 22 is L, the radius of curvature of the incident surface 21 is r, and the angle between the sidewall of the homogenizing component 2 located in the fast axis direction of the quasi-flat-top beam and the cross-section of the crystal rod 8 is α. The initial beam intensity distribution is represented as 10000 discrete light points in a two-dimensional coordinate system, corresponding to a simplified dataset S(x,y), where the maximum value of x and y is 10000. The correlation function is then F(L,r,a). S(x,y)=Q1, where the maximum value of x and y is 10000.

[0092] Assume that the light emitted from the first modulator 3 obeys Q2= The Q2 matrix is ​​the correlation function of the first modulator 3. Let T(x,y) be the function of the gradient transmittance of the first modulator 3, where the maximum value of x and y is 10000. Then we have T(x,y). Q1 = Q2.

[0093] When a matrix ray obeying the Q2 intensity is incident on crystal rod 8, the diameter, doping concentration, refractive index, and surface scattering of crystal rod 8 all affect the absorption uniformity. To simplify the calculation, a function is assumed to include these variables, i.e., the diameter of crystal rod 8 is D, the doping concentration is c, the refractive index is n, and the surface scattering follows a simplified Lambertian scattering model, SL. Then, the expression for crystal rod 8 is YAG(D,c,n,S). L When we disregard primary absorption (ignoring the absorption of light emitted from the first modulator 3 as it passes through the crystal rod 8 once), and only consider the intensity distribution of light ultimately absorbed by the crystal rod 8 after passing through the first modulator 3, let the reflection form of the reflectivity of the second modulator 10 be given by the function S. P (x,y) represents YAG(D,c,n,SL). Q2 S P (x,y)=Q3, substituting into the expressions Q2 and Q1, we get YAG(D,c,n,SL). T(x,y) F(L,r,a) S(x,y) S P (x,y)=Q3, where Q3 is the desired fluorescence distribution matrix, and Q3= ,

[0094] At this point, let p1=p2=p3…….= p10000. The root mean square error (RMS) is less than a set value, for example, less than 0.01, meaning the difference in light intensity does not exceed the calculated standard deviation of 0.01. Then, let the computer fit the optimal expressions for T(x,y) and S(x,y). T(x,y) and S(x,y) are the decay functions of the gradient transmittance of the first modulator 3 and the reflectance of the second modulator 10.

[0095] In existing lasers, such as 1064nm solid-state lasers, a side-pump source is often composed of an 808nm wavelength semiconductor laser (light-emitting structure 1), with an ND:YAG crystal rod as the laser gain medium, outputting 1064nm laser light. The fluorescence uniformity of the crystal rod within the system greatly affects the beam quality of the 1064nm laser. Furthermore, in high-power side-pumping systems, poor fluorescence uniformity can easily cause the crystal rod to break. Moreover, in such high-power side-pumping, the gain crystal rods used are often large in diameter. To obtain high fluorescence uniformity, multi-dimensional pump structures, such as 7-dimensional or 13-dimensional ones, must be employed, which not only increases structural complexity but also increases heat dissipation pressure. The pump system in this embodiment overcomes these drawbacks. The system does not require a complex combination of optical components; it only requires light-emitting structure 1, homogenization component 2, first modulation device 3, second modulation device 10, and crystal rod 8. The fluorescence uniformity of crystal rod 8 can be achieved through this structure, eliminating the need for excessive laser modules and a thick crystal rod 8, greatly reducing the system's heat dissipation burden, simplifying the structure, and lowering costs.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A side-pumping system for a semiconductor laser, characterized in that, include: A crystal rod (8) and multiple sets of laser modules, wherein the multiple sets of laser modules are arranged circumferentially around the outer side of the crystal rod (8); Each laser module includes a light-emitting structure (1), a homogenizing component (2), a first modulation device (3), and a second modulation device (10). The light-emitting structure (1), the homogenizing component (2), and the first modulation device (3) are all located on one side of the crystal rod (8), and the second modulation device (10) is located on the opposite side of the crystal rod (8). The light-emitting structure (1), the homogenizing component (2), and the first modulation device (3) are arranged sequentially from the center of the crystal rod (8) to the center away from the crystal rod (8). The light-emitting structure (1) is used to emit an initial light beam toward the homogenizing component (2); The homogenization component (2) is used to shape the initial beam into a flat-top beam and output it to the first modulation device (3). The first modulation device (3) is used to shape the flat-top beam so that the flat-top beam is shaped into a bowl-shaped beam with a higher attenuation rate in the middle than attenuation rate at the edge. The bowl-shaped beam enters the crystal rod (8) from one side. The bowl-shaped beam passing through the crystal rod (8) exits from the opposite side of the crystal rod (8) and is directed toward the second modulation device (10). Based on the optical properties of the crystal rod (8), the second modulation device (10) is configured to shape the bowl-shaped beam into incident light with a middle reflectivity lower than the edge reflectivity and output it to the crystal rod (8). The first modulation device (3) includes a light-transmitting film (9) with gradually varying transmittance. The light-transmitting film (9) is located between the homogenizing component (2) and the crystal rod (8). The transmittance of the light-transmitting film (9) gradually increases from the center to the edge. The second modulation device (10) includes a polarization film layer (4), the reflective surface of the polarization film layer (4) is curved, and the polarization film layer (4) and the first modulation device (3) are located on opposite sides of the crystal rod (8) in the radial direction. The polarizing film layer (4) is used to reflect the S-ray in the bowl-shaped beam. The reflectivity of the polarizing film layer (4) gradually increases from the center to the edge.

2. The semiconductor laser side-pumping system according to claim 1, characterized in that, The transmittance of the light-transmitting film (9) ranges from 0.84 to 1.

3. The semiconductor laser side-pumping system according to claim 1, characterized in that, The reflectivity of the polarizing film layer (4) ranges from 0.88 to 1.

4. The semiconductor laser side-pumping system according to claim 1, characterized in that, The second modulation device (10) includes an annular light-transmitting tube (5), which is located on the circumferential outer side of the crystal rod (8) and on the inner side of a plurality of first modulation devices (3) arranged in an annular shape. Multiple polarizing film layers (4) are attached to the tube wall of the annular light-transmitting tube (5) on the side facing the crystal rod (8).

5. The semiconductor laser side-pumping system according to any one of claims 1-4, characterized in that, The homogenization component (2) is located between the light-emitting structure (1) and the first modulation device (3). The homogenization component (2) includes a light-incident surface (21) and a light-emitting surface (22). The light-incident surface (21) faces the light-emitting structure (1), and the light-emitting surface (22) faces the first modulation device (3). The light-emitting surface (22) includes a curved portion, which is arranged along the fast axis direction of the flat-top beam and is recessed toward the light-emitting surface (22). High-reflectivity films (7) are provided on both sides of the homogenizing component (2) in the fast axis direction of the flat-top beam; the distance between the two sides of the homogenizing component (2) in the fast axis direction of the flat-top beam gradually decreases from the light-incident surface (21) toward the light-outceasing surface (22).

6. The semiconductor laser side-pumping system according to claim 5, characterized in that, The radius of curvature of the curved surface portion ranges from 4mm to 20mm; And / or, the vertical distance between the most concave position of the curved surface portion and the light-emitting surface (22) is in the range of 4-10 mm.

7. The semiconductor laser side-pumping system according to any one of claims 1-4, characterized in that, The light-emitting structure (1) includes multiple light-emitting units arranged at intervals, and the spacing between two adjacent light-emitting units ranges from 0.7mm to 1.2mm. And / or, the range of the fast axis divergence angle of the light-emitting unit is 50°-60°; And / or, the number of light-emitting points of the light-emitting unit ranges from 19 to 63 points; And / or, the diameter of the crystal rod (8) is in the range of 10mm-20mm; And / or, the doping concentration of the crystal rod (8) ranges from 0.4 at% to 1 at% And / or, the optical properties of the crystal rod (8) include at least one of refractive index, doping concentration and diameter; And / or, the number of laser modules is three or five; And / or, a heat dissipation structure (6) is provided between the second modulation device (10) and the crystal rod (8).

8. A method for fabricating a side-pumping system for a semiconductor laser, characterized in that, To prepare the semiconductor laser side-pumping system according to any one of claims 1-7, the steps include: Based on the light intensity distribution of the initial beam, the optical properties of the homogenizing component (2), and the desired fluorescence distribution of the crystal rod (8), the decay form of the gradient transmittance of the first modulation device (3) and the reflection form of the reflectance of the second modulation device (10) are obtained. The first modulation device (3) and the second modulation device (10) are prepared according to the decay mode and the reflection mode.

9. The method for fabricating a semiconductor laser side-pumping system according to claim 8, characterized in that, The decay form of the gradient transmittance of the first modulation device (3) is represented by the function T(x,y); the reflection form of the reflectance of the second modulation device (10) is represented by the function S. P (x,y) represents; According to the following formula: F*S(x,y)=Q1; T(x,y)*Q1=Q2; YAG*Q2* S P (x,y)=Q3; Obtain functions T(x,y) and S. P (x,y); where S(x,y) is the light intensity distribution matrix of the initial beam, Q1 is the light intensity distribution matrix of the flat-top beam, F is the expression of the optical properties of the homogenization component (2), Q2 is the light intensity distribution matrix of the bowl-shaped beam, YAG is the expression of the optical properties of the crystal rod (8), Q3 is the desired fluorescence distribution matrix, and S(x,y), F, and YAG are known, and Q3 is a set quantity.

10. The method for fabricating a semiconductor laser side-pumping system according to claim 9, characterized in that, The homogenizing component (2) is located between the light-emitting structure (1) and the first modulation device (3). The homogenizing component (2) includes an incident surface (21) and an exit surface (22). The exit surface (22) includes a curved surface portion. In the radial direction of the crystal rod (8), the distance between the most concave position of the incident surface (21) and the exit surface (22) is L. The radius of curvature of the incident surface (21) is r. The angle between the sidewall of the homogenizing component (2) located in the fast axis direction of the quasi-flat-top beam and the cross section of the crystal rod (8) is a. Then the expression of the optical properties of the homogenizing component (2) is F(L,r,a). And / or, the crystal rod (8) has a diameter of D, a doping concentration of c, a refractive index of n, and surface scattering follows a simplified Lambertian scattering model, i.e., S L Then the expression for the optical properties of the crystal rod (8) is YAG(D,c,n,S) L ); And / or, suppose the light intensity distribution of the initial beam is represented as the set of light intensities of k discrete light points in a two-dimensional coordinate system, and set the root mean square error (RMS) of the light intensities of the k light points in Q3 to be less than a set amount, so as to fit and obtain Q3.

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