A fiber laser for outputting an array of dots of laser light

Abstract

The application relates to a fiber laser for outputting a dot array laser, comprising a pump source module for emitting pump light; a random mixing pump coupler, which internally forms a sealed cavity; the inner wall of the sealed cavity is provided with an optical diffuse reflection surface, which is composed of micro-optical structure units with a feature size greater than the wavelength of the pump light and arranged in an asymmetric and non-periodic manner, and is used for deterministic and diversified directional transformation of the incident pump light; a fiber array gain module, which comprises a plurality of array-arranged gain optical fibers; the middle sections of the gain optical fibers are removed of coating layers and placed in the sealed cavity; and a resonant cavity mirror module, which comprises input cavity mirrors and output cavity mirrors arranged at the two ends of the fiber array gain module. The application can improve the uniformity of pump energy in the region of the gain optical fibers and improve the intensity uniformity of the dot array output light spot.

Description

Technical Field

[0001] This application relates to the field of laser equipment technology, and in particular to a fiber laser for outputting a dot array laser. Background Technology

[0002] Point array lasers are a technology that simultaneously outputs multiple discrete, high-brightness laser spots. They offer unique advantages such as parallel processing, rapid optical sensing, and structured illumination, and are becoming a hot topic in cutting-edge research and industrial applications. To achieve high-power point array laser output, multi-fiber array lasers are typically used. Multiple independent gain fibers are integrated in a tightly packed array and driven by a unified pump source and resonant structure, thereby increasing the total output power and obtaining an arrayed laser output spot.

[0003] Currently, existing technologies suffer from the following technical problems: Firstly, there is an issue with the uniformity of pump energy distribution within the array. Traditional solutions often employ side pumping, which can lead to spatial non-uniformity in the energy distribution of the pump light after it enters the array. This results in excessively strong pumping on fibers located at the array edges or directly facing the pump source, while fibers located at the array center or facing away from the pump source receive insufficient pumping. This causes problems such as thermal management imbalance, efficiency loss, and degraded output performance. Secondly, the uniformity of pump energy also affects the intensity uniformity of the output light spot in the point array.

[0004] Therefore, there is a need for a fiber laser for output point array laser that can improve the uniformity of pump energy distribution and enhance the uniformity of array output spot. Summary of the Invention

[0005] Therefore, it is necessary to provide a fiber laser for outputting point array lasers, and its specific technical solution is as follows.

[0006] A fiber laser for outputting a dot array laser, comprising:

[0007] Pump source module, used to emit pump light;

[0008] A random hybrid pump coupler forms a sealed cavity inside; the inner wall of the sealed cavity has an optical diffuse reflection surface, which is composed of micro-optical structural units with characteristic dimensions larger than the pump light wavelength and arranged asymmetrically and aperiodically, for deterministic and diversified directional transformation of the incident pump light.

[0009] A fiber array gain module includes multiple gain fibers arranged in an array; the middle section of the gain fibers has its coating removed and is placed in a sealed cavity;

[0010] The resonant cavity mirror module includes an input cavity mirror and an output cavity mirror located at both ends of the fiber array gain module.

[0011] Furthermore, the micro-optical structure unit is at least one of a microprism, a microlens, or a fractal structure.

[0012] Furthermore, the microprism is a right-angle prism with a random distribution of inclined plane angles between 30° and 60°, or an irregular triangular prism with a random position offset and angle rotation grid.

[0013] Furthermore, the microlenses have a circular aperture, and the focal length of each microlens is randomly set within ±10% of the design value; the microlenses are arranged in a close hexagonal pattern with random positional perturbations.

[0014] Furthermore, the sealed cavity is filled with a thermally conductive fluid, which is transparent and has a refractive index not higher than that of the gain fiber cladding.

[0015] Furthermore, the pump source module includes multiple laser diodes with different emission wavelengths, and the multiple random hybrid pump couplers are arranged with circumferential non-uniform angular spacing.

[0016] Furthermore, the pump source module also includes a driving circuit; the driving circuit includes a signal generator and a plurality of corresponding voltage-controlled current sources; the signal generator is used to generate N periodic modulation signals with the same frequency and a preset fixed phase difference between them; each modulation signal is independently input to a corresponding voltage-controlled current source, and the voltage-controlled current source outputs a driving current superimposed on the modulation signal to drive a corresponding laser diode.

[0017] Furthermore, the phase difference of the N modulation signals is uniformly distributed according to Φ_i=(2π / N)*i, where i is the channel number and Φ_i represents the phase value of the i-th modulation signal.

[0018] Furthermore, the spacing between the cores of adjacent gain fibers is 3-5 times the core diameter, in order to achieve a power coupling coefficient of 10. -4 Up to 10 -2 Weak optical coupling within the range.

[0019] Furthermore, it also includes a built-in mode control element, which is located between the output end of the fiber array gain module and the output cavity mirror; the built-in mode control unit includes a correction unit corresponding to the gain fiber, which is used to correct the aberration of the laser output by the corresponding gain fiber.

[0020] Furthermore, the output cavity mirror includes a reflective film; the reflective film includes multiple reflective units that correspond one-to-one with the gain fiber and are arranged independently, and the reflectivity of the multiple reflective units is arranged according to a preset rule; the preset rule is: with the optical center of the arrayed gain fiber as the origin, the reflectivity of each reflective unit decreases gradually as its distance from the center increases.

[0021] Furthermore, the middle section of the gain fiber is provided with an anti-reflection coating, and the refractive index of the anti-reflection coating gradually decreases from the inside to the outside.

[0022] Furthermore, the sealed cavity is ellipsoidal in shape, and the middle section of the gain fiber removing the coating is located near one focus of the ellipsoid.

[0023] Beneficial effects: The fiber laser for outputting a point array laser provided by this invention enables the pump light emitted from the pump source to undergo deterministic and diverse direction transformations within the sealed cavity of the random hybrid pump coupler under the action of micro-optical structural units. This actively drives the optical field to achieve ultra-fast randomization within the cavity. Compared with traditional diffuse reflection coatings, this invention can more actively and drastically disrupt the optical path, physically creating an extremely complex optical path network. This allows the optical field to reach a highly chaotic mixed state in a very short time, thereby improving the pump energy uniformity in the region where the gain fiber is located. This ensures that each fiber receives statistically identical pump intensity from all directions, thus improving the intensity uniformity of the point array output spot. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A schematic diagram of the functional modules of a fiber laser;

[0026] Figure 2 This is a schematic diagram of the structure of a fiber laser;

[0027] Figure 3 for Figure 2 A cross-sectional view along the middle AA line;

[0028] Figure 4 A schematic diagram of the built-in mode control element;

[0029] Figure 5 This is a schematic diagram of the driver circuit logic.

[0030] Explanation of reference numerals in the attached diagram: 1. Pump source module; 2. Random hybrid pump coupler; 3. Gain fiber; 4. Input cavity mirror; 5. Output cavity mirror; 6. Built-in mode control element;

[0031] 11. Sealed cavity; 12. Optical diffuse reflection surface; 13. Micro-optical structure unit; 14. Coolant microchannel;

[0032] 61. Calibration unit;

[0033] 71. Signal generator; 72. Voltage-controlled current source; 73. Laser diode. Detailed Implementation

[0034] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0035] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, 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 of this application.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0037] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0038] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0039] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0040] Example

[0041] Reference Figure 1-4 As shown, this embodiment provides a fiber laser for outputting a point array laser, including a pump source module 1, a random hybrid pump coupler 2, a fiber array gain module, and a resonant cavity mirror module. The pump source module 1 is disposed on the side of the random hybrid pump coupler 2 for injecting pump light from the side.

[0042] Specifically, the random hybrid pump coupler 2 forms a sealed cavity 11. The inner wall of the sealed cavity 11 has an optical diffuse reflection surface 12, which is composed of micro-optical structural units 13 with characteristic dimensions larger than the pump light wavelength and arranged asymmetrically and aperiodically. These units are used to perform deterministic and diverse direction transformations on the incident pump light. It should be noted that the characteristic dimensions refer to the typical physical dimensions of the micro-optical structural units 13, such as width, depth, and diameter. If the micro-optical structural unit 13 is a microprism, the characteristic dimensions refer to its depth and width; if it is a microlens, the characteristic dimensions refer to its diameter; if it is a fractal structure, the characteristic dimensions refer to the width of the smallest branch or groove in the fractal iteration. In this embodiment, the characteristic dimensions of the micro-optical structural units 13 are much larger than the pump light wavelength to ensure that the pump light forms an optical effect dominated by geometric optical reflection. Each micro-optical structural unit 13 is a deterministic direction converter, ensuring the determinism of the pump light direction.

[0043] When the pump light emitted from the pump source is injected into the sealed cavity 11, it undergoes multiple random reflections by the micro-optical structure units 13, forming a uniformly distributed light bath in space and improving the uniformity of the pump energy distribution. Since the characteristic size of the micro-optical structure units 13 is larger than the wavelength of the pump light, the pump light is primarily reflected by geometric optics. The direction of the pump light can be actively, deterministically, and programmatically manipulated, allowing each pump light beam to change its path according to classical optical laws under the action of countless carefully designed micro-optical structure units 13. The asymmetric and non-periodic arrangement design means that beams with the same incident angle, after reflection by different micro-optical structure units 13, will exit at a large number of different and unpredictable angles, with no discernible pattern. This reflection through a large number of deterministic and diverse micro-optical structure units 13 can completely disrupt the optical path to a chaotic state in a very short time, resulting in high efficiency and controllability. Compared to traditional diffuse reflection, the micro-optical structure units 13 used in this embodiment can actively and programmatically reflect and redistribute the incident pump light. They can more effectively disrupt the propagation direction of the pump light, enabling it to achieve a fully randomized mixing state within a shorter path, thereby improving the randomization efficiency and uniformity of the pump light, while potentially reducing cavity size and unwanted absorption losses of the pump light.

[0044] Specifically, the fiber array gain module includes multiple gain fibers 3 arranged in an array; the middle section of the gain fiber 3 has its coating removed and is placed inside a sealed cavity 11. The resonant cavity mirror module includes an input cavity mirror 4 and an output cavity mirror 5 disposed at both ends of the fiber array gain module.

[0045] Multiple arrayed gain fibers 3, with their coating removed, absorb pump energy uniformly from the side within a sealed cavity 11 where pump light is evenly distributed. This causes population inversion in the doped ions, generating stimulated emission. Within a resonant cavity formed by mirrors at both ends, the stimulated emission light is amplified and oscillates before finally exiting through the output mirror. By improving the uniformity of pump energy distribution, the uniformity of pump energy absorption by the multiple arrayed fibers is improved, avoiding problems such as thermal management imbalance, efficiency loss, and output performance degradation, and enhancing the intensity uniformity of the point array laser output spot.

[0046] The fiber laser for outputting a point array laser provided in this embodiment enables the pump light emitted from the pump source to undergo deterministic and diverse direction transformations within the sealed cavity 11 of the random mixing pump coupler 2, under the action of the micro-optical structure unit 13. This actively drives the optical field to achieve ultra-fast randomization within the cavity. Compared to traditional diffuse reflection coatings, this method can more actively and drastically disrupt the optical path, physically creating an extremely complex optical path network. This allows the optical field to reach a highly chaotic mixed state in a very short time, thereby improving the pump energy uniformity in the region where the gain fiber 3 is located. This ensures that each fiber receives statistically identical pump intensity from all directions, thus improving the intensity uniformity of the point array output light spot.

[0047] In one embodiment, the micro-optical structure unit 13 is at least one of a microprism, a microlens, or a fractal structure. That is, the inner wall of the sealed cavity 11 forms a microprism array, a microlens array, or a fractal structure surface. Specifically, it can be fabricated using microfabrication techniques such as ultrafast laser processing.

[0048] In one embodiment, the optical diffuse reflection surface 12 is an array of microprisms formed on the inner wall of the cavity using microfabrication techniques. These microprisms are non-equilateral and non-stacked. For example, right-angled prisms with randomly distributed inclined planes between 30° and 60°, or irregular triangular prisms with random positional offsets and angular rotation grids can be used.

[0049] In one embodiment, the microprism is triangular prism-shaped, with the included angle between the two reflecting surfaces randomly distributed between 90° and 130°, and the rotation angle of the microprism randomly set within the range of 0°-360°. The microprisms are arranged quasi-periodically on the substrate in a hexagonal close-packed grid. Specifically, based on the regular grid nodes, the position of each microprism is randomly offset by ±15% of the grid spacing in the X and Y directions, while its own rotation angle is random. This design completely avoids any periodic diffraction or interference effects, thereby improving the uniformity of the pump energy distribution. The width of the microprism is between 20μm and 150μm, and the depth is between 10μm and 100μm. Its characteristic dimensions are much larger than the pump light wavelength, causing the pump light to form an optical effect dominated by geometric optical reflection.

[0050] In one embodiment, the optical diffuse reflection surface 12 is an array of microlenses formed on the inner wall of the cavity using microfabrication techniques. These microlenses have circular apertures and can be aspherical or freeform. The focal length of each microlens is randomly set within ±10% of the design value, for example, from 180 μm to 220 μm. The microlenses are arranged in a close-packed hexagonal configuration with random positional perturbations. The incident pump beam is independently converged or diverged by each microlens, forming numerous sub-beams with different focal positions and propagation directions. These sub-beams propagate and overlap within the cavity space, and further interact with and scatter with structures on other walls. This active, parameter-randomized beam splitting and redistribution mechanism physically creates an extremely complex optical network, causing the light field to reach a highly chaotic mixed state in a very short time.

[0051] In one embodiment, the sealed cavity 11 is filled with a heat-conducting fluid that is transparent and has a refractive index no higher than that of the cladding of the gain fiber 3. The middle section of the fiber array gain module is immersed in the heat-conducting fluid. Because the refractive index of the heat-conducting fluid is no higher than that of the fiber cladding, the relatively low refractive index of the heat-conducting fluid eliminates the total internal reflection barrier when pump light enters the fiber cladding interface from the fluid, allowing the pump light to efficiently penetrate the cladding. This refractive index relationship ensures that pump light incident on the side of the fiber from all directions, regardless of its incident angle, will not undergo total internal reflection at the fluid-cladding interface. According to Snell's law, all light rays can pass through the interface into the cladding and be efficiently absorbed by the doped ions within the cladding. This design eliminates the total internal reflection barrier, allowing pump photons in the optical bath to penetrate the fiber with the highest probability, which is the physical basis for achieving high-efficiency side pump coupling. The heat-conducting fluid rapidly conducts the waste heat generated after the gain fiber receives pump photons, as well as the heat absorbed by the cavity itself, away from the laser. This achieves efficient side coupling of the pump light and effective thermal management of the system, preventing thermal lensing effects and thermal degradation of the gain medium, further improving pump uniformity, and ensuring long-term operation of the laser.

[0052] In one embodiment, the gain fiber 3 is clad in pure silica with a refractive index of approximately 1.45, and the thermally conductive fluid is an inert dielectric fluid with a refractive index between 1.25 and 1.40 and a thermal conductivity of not less than 0.05 W / (m·K).

[0053] In one embodiment, the heat-conducting fluid is at least one of a fluorinated carbon compound, a low-refractive-index silicone oil, or ultrapure deionized water.

[0054] Reference Figure 3As shown, the housing of the random hybrid pump coupler 2 is provided with coolant microchannels 14 surrounding the sealed cavity 11. Heat is conducted from the gain fiber 3 to the inner wall of the sealed cavity 11 via a heat-conducting fluid, and then carried away from the cavity wall by the coolant within the microchannels. This improves the system's heat dissipation capacity and power limit, ensuring stable high-power operation.

[0055] In one embodiment, the pump source module 1 includes multiple laser diodes 73 with different emission wavelengths, and the multiple random hybrid pump couplers 2 are arranged with non-uniform circumferential angular spacing. The wavelength difference between each laser diode 73 ranges from 0.5 nm to 5 nm. For example, six laser diodes 73 are used as the pump source, and the doped ion is Yb. 3+ Yb 3+ The ion absorption peak is at 976 nm. The emission wavelengths of each laser diode 73 are screened and pseudo-randomly distributed within the range of 974.5 nm to 977.5 nm. Specific wavelength values ​​are set as follows: 974.7 nm, 975.3 nm, 976.1 nm, 976.8 nm, 977.3 nm, and 975.9 nm. The minimum difference between adjacent wavelengths is 0.5 nm, and the maximum difference is 0.8 nm. There is no fixed interval; the pseudo-random distribution of multiple wavelengths results in an overall absorption spectrum wider than a single wavelength. Different wavelengths exhibit different absorption coefficients and depths in ytterbium-doped fiber: shorter wavelengths are absorbed more strongly at the fiber tip, while longer wavelengths penetrate deeper. This combination makes the absorption distribution of pump energy along the fiber axis or longitudinal direction smoother and more uniform, effectively avoiding local hot spots and strong thermal lensing effects caused by excessive absorption at the fiber tip. The angular position arrangement abandons the equal spacing rule and uses a pre-calculated sequence of angle increments with no common divisor for positioning. Specifically, starting from a 0° reference point, the six laser diodes (73) are non-uniformly distributed across the entire circumference by rotating sequentially by 41°, 137°, 173°, 223°, and 293°. The ratio of any two angular increments in this sequence is not a simple integer, geometrically destroying rotational symmetry. This non-uniform angular spacing ensures that the pump light is disordered from its spatial injection source. It completely eliminates the angle-dependent periodic intensity modulation modes that might occur with uniform arrangement. Through this dual non-uniform design of the spectrum and space, a deep optimization of the pump light intensity and thermal load distribution within the gain medium is achieved at the physical mechanism level. Optimizing pump uniformity from both spectral and spatial dimensions significantly improves thermal distribution and reduces thermal lensing effects, thereby enhancing the beam quality and long-term stability of the output laser.

[0056] In one embodiment, reference Figure 5As shown, the pump source module 1 further includes a driving circuit; the driving circuit includes a signal generator 71 and a plurality of corresponding voltage-controlled current sources 72; the signal generator 71 is used to generate N periodic modulation signals with the same frequency and a preset fixed phase difference between them; each modulation signal is independently input to a corresponding voltage-controlled current source 72, and the voltage-controlled current source 72 outputs a driving current superimposed on the modulation signal to drive a corresponding laser diode 73. The intensity of the pump light of each diode changes periodically with different phases over time, so that the population inversion distribution in the gain medium is in a dynamic equilibrium state, effectively suppressing the gain non-uniformity caused by the local consumption of gain due to laser oscillation.

[0057] In one embodiment, the phase difference of the N modulation signals is uniformly distributed according to Φ_i = (2π / N)*i, where i is the channel number and Φ_i represents the phase value of the i-th modulation signal. For example, in a 7-channel system, the phase differences are 0°, 51.4°, 102.9°, 154.3°, 205.7°, 257.1°, and 308.6°, respectively. This introduces cooperative dynamic modulation in the time domain on top of the non-uniform spectrum and spatial distribution of the pump light. During operation, the light intensity of the N pump points undergoes periodic slight variations with the same frequency but different phases. At any given moment, the light intensity of some laser diodes 73 is at a peak, some at a trough, and some at an intermediate value, but the sum of the total output light power of all laser diodes 73 remains nearly constant. This time-controlled pump light, injected into the random hybrid pump coupler 2, further provides a time-varying and spatially staggered pump profile for the gain fiber 3, building upon the already achieved spatial homogenization of pump energy. Laser oscillations will form fixed, severely depleted spatial holes in the gain medium. In this embodiment, due to the periodic variation of pump intensity in time and space, the positions of these spatial holes are dynamically refilled and relocated. When the gain decreases at a certain point due to laser extraction, the time-varying light intensity from pump sources of different phases ensures that a relatively stronger pump will soon compensate for this, thus preventing the stable formation of static holes. The population inversion distribution within the gain medium is forced into a dynamic equilibrium state, and its time-averaged distribution becomes extremely uniform. This fundamentally smooths the gain, significantly improving the power stability and uniformity of the output laser, especially among the channels of the array.

[0058] In one embodiment, the spacing between the cores of adjacent gain fibers 3 is 3-5 times the core diameter, to achieve a power coupling coefficient of 10. -4 Up to 10 -2Weak optical coupling within the range improves mechanical stability. This weak coupling can provide some gain equalization between channels and may suppress aberrant modes in individual channels without causing strong mode competition, thus contributing to the brightness uniformity of the output array. In this embodiment, multiple gain fibers 3 are tightly arranged and integrated in an array-like geometry, using a one-piece molding process.

[0059] In one embodiment, the laser further includes a built-in mode control element 6, located between the output end of the fiber array gain module and the output cavity mirror 5. The built-in mode control element includes a correction unit 61 corresponding to each gain fiber 3, used to correct aberrations in the laser output from the corresponding gain fiber 3. By optimizing the curvature and angle of the beams emitted from each gain fiber 3 through the correction unit 61, the divergent beams are precisely collimated, and wavefront distortion is effectively corrected, resulting in a nearly circular, energy-concentrated beam. Through high-precision processing and assembly, the entire system achieves near-diffraction-limited beam quality for each channel, resulting in a nearly ideal beam output effect. More precise control of the wavefront of each output beam yields a smaller divergence angle and a more perfect beam, raising the beam quality of a single channel to near the theoretical limit.

[0060] In one embodiment, the built-in mode control unit is a microlens array or a low-loss optical waveguide network formed by femtosecond laser direct writing technology.

[0061] In one embodiment, the output cavity mirror 5 includes a reflective film; the reflective film includes multiple reflective units, each corresponding to and independently arranged with respect to the gain fiber 3, and the reflectivity of the multiple reflective units is arranged according to a preset rule; the preset rule is that, with the optical center of the arrayed gain fiber 3 as the origin, the reflectivity of each reflective unit gradually decreases as its distance from the center increases. The laser threshold is controlled by the reflectivity to compensate for inherent non-uniformity.

[0062] For example, the reflectivity of the central region is designed to be 99.5%, the reflectivity of the outermost region is designed to be 98.0%, and the middle region smoothly transitions linearly or as a Gaussian function according to distance. In solid-state lasers, the laser oscillation threshold is directly related to the reflectivity of the output mirror; the higher the reflectivity, the lower the threshold. Under traditional uniform reflectivity cavity mirrors, due to the slight edge attenuation effect of the pump bath and the difference in heat dissipation conditions from the center to the edge, the actual pump intensity and heat dissipation efficiency obtained by the gain medium of the array edge channels are usually slightly lower than those of the central channel. This leads to a higher actual laser threshold and lower output power. This embodiment actively reduces the laser oscillation threshold of the central channel by giving the central region a higher reflectivity. Under the same pump intensity, the central channel oscillates first and consumes gain due to its lower threshold. This, to some extent, suppresses the excessive extraction of gain by the central channel, allowing more inverted particle number to be utilized by the edge channels, thereby balancing the inherent gain difference between the edge and the center caused by pump and thermal effects.

[0063] In one embodiment, the gain fiber 3 has an anti-reflection coating on the outer side of the middle section after removing the coating layer. The refractive index of the anti-reflection coating gradually decreases from the inside to the outside. This further reduces Fresnel reflection loss when pump light enters the fiber cladding from the fluid, improving pump coupling efficiency, especially at interfaces with high refractive index differences.

[0064] In one embodiment, the sealed cavity 11 is ellipsoidal in shape, and the middle section of the gain fiber 3 (without coating) is located near one focal point of the ellipsoid. Based on the optical properties of the ellipsoid, light emitted from one focal point is reflected by the inner wall and converges to another focal point. The pump source can be approximated as being located near the other focal point, and its light, after reflection, converges more concentratedly at the location of the fiber array. While maintaining randomness, a certain focusing effect is introduced, improving the utilization efficiency of the pump light. This allows for the use of a lower-power pump source to achieve the same gain effect, or to obtain higher power output under the same pumping conditions.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A fiber laser for outputting a point array laser, characterized in that, include: Pump source module, used to emit pump light; A random hybrid pump coupler forms a sealed cavity inside; the inner wall of the sealed cavity has an optical diffuse reflection surface, which is composed of micro-optical structural units with characteristic dimensions larger than the pump light wavelength and arranged asymmetrically and aperiodically, for deterministic and diversified directional transformation of the incident pump light. A fiber array gain module includes multiple gain fibers arranged in an array; the middle section of the gain fibers has its coating removed and is placed in a sealed cavity; The resonant cavity mirror module includes an input cavity mirror and an output cavity mirror disposed at both ends of the fiber array gain module; The micro-optical structure unit is at least one of microprism, microlens, and fractal structure; The microprism is a right-angle prism with a random distribution of inclined plane angles between 30° and 60°, or an irregular triangular prism with a random position offset and angle rotation grid. The microlenses have a circular aperture, and the focal length of each microlens is randomly set within ±10% of the design value; the microlenses are arranged in a close hexagonal pattern with random positional perturbations. The pump source module includes multiple laser diodes with different emission wavelengths, and the multiple random hybrid pump couplers are arranged with non-uniform circumferential angular spacing. The gain fiber has an anti-reflection coating on the outer side of the middle section of the decoating layer, and the refractive index of the anti-reflection coating gradually decreases from the inside to the outside. The sealed cavity is ellipsoidal in shape, and the middle section of the gain fiber removing the coating is located near one focus of the ellipsoid.

2. A fiber laser for outputting a point array laser according to claim 1, characterized in that, The sealed cavity is filled with a heat-conducting fluid, which is transparent and has a refractive index no higher than that of the cladding of the gain fiber.

3. A fiber laser for outputting a point array laser according to claim 1, characterized in that, The pump source module also includes a driving circuit; the driving circuit includes a signal generator and a plurality of corresponding voltage-controlled current sources; the signal generator is used to generate N periodic modulation signals with the same frequency and a preset fixed phase difference between them; each modulation signal is independently input to a corresponding voltage-controlled current source, and the voltage-controlled current source outputs a driving current superimposed on the modulation signal to drive a corresponding laser diode.

4. A fiber laser for outputting a point array laser according to claim 3, characterized in that, The phase difference of the N modulation signals is uniformly distributed according to Φ_i=(2π / N)*i, where i is the channel number and Φ_i represents the phase value of the i-th modulation signal.

5. A fiber laser for outputting a point array laser according to claim 1, characterized in that, The spacing between the cores of adjacent gain fibers is 3-5 times the core diameter to achieve a power coupling coefficient of 10. -4 Up to 10 - Weak optical coupling within a 2-range.

6. A fiber laser for outputting a point array laser according to claim 1, characterized in that, It also includes a built-in mode control unit, which is located between the output end of the fiber array gain module and the output cavity mirror; the built-in mode control unit includes a correction unit corresponding to the gain fiber, which is used to correct the aberration of the laser output by the corresponding gain fiber.

7. A fiber laser for outputting a point array laser according to claim 1, characterized in that, The output cavity mirror includes a reflective film; the reflective film includes multiple reflective units that correspond one-to-one with the gain fiber and are arranged independently, and the reflectivity of the multiple reflective units is arranged according to a preset rule; the preset rule is: with the optical center of the arrayed gain fiber as the origin, the reflectivity of each reflective unit decreases gradually as its distance from the center increases.

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