Laser amplification device

Abstract

The application discloses a laser amplification device, and relates to the technical field of lasers.The laser amplification device comprises a laser light source, a dispersion member, a gain crystal and a pump light source.The dispersion member is used for spatially dispersing laser light generated by the laser light source, so that different wavelength components of the laser light are spatially separated along a first direction.The gain crystal is arranged on the light path of the laser light after dispersion and has a first region and a second region along the first direction, wherein the activated ion doping concentration of the first region is lower than that of the second region.The laser light after dispersion is incident to the first region and the second region, and the wavelength of the laser light incident to the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident to the second region.By arranging the laser light component close to the gain peak wavelength to be incident to the low-doping region and the laser light component far from the gain peak wavelength to be incident to the high-doping region, the gain of different wavelength components can be balanced, the gain narrowing effect can be inhibited, and the spectral width of the amplified laser light can be maintained.

Description

Technical Field

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

[0002] Femtosecond lasers possess ultra-high peak power and ultra-short pulse duration, offering significant advantages in fields such as brittle material processing, high-harmonic generation, and nonlinear frequency conversion light sources. Narrow pulse width is one of the key factors in achieving these applications. According to the Fourier transform limit, the pulse temporal width is inversely proportional to the spectral width; therefore, obtaining a wide-spectral output is an important prerequisite for realizing narrow-pulse femtosecond lasers.

[0003] However, during laser amplification, the laser spectrum will narrow due to the gain narrowing effect. Summary of the Invention

[0004] The purpose of this application is to provide a laser amplification device to improve the technical problem of laser spectrum narrowing during laser amplification in the prior art.

[0005] To achieve the above objectives, the technical solution adopted in this application is: to provide a laser amplification device, which includes: Laser source; laser source is used to generate laser light; Dispersion element; a dispersion element is used to spatially disperse laser light incident from a laser source, so that different wavelength components of the laser light are spatially separated along a first direction; Gain crystal; The gain crystal is placed in the optical path of the laser after dispersion by the dispersive element to amplify the dispersed laser. The gain crystal is doped with activating ions. Pump source; The pump source is used to output pump light and emit it to the gain crystal, providing pump energy for the gain crystal to amplify the laser; Along the first direction, the gain crystal has a first region and a second region, wherein the doping concentration of active ions in the first region is lower than that in the second region. The laser light, after being dispersed by the dispersive element, is incident on the first region and the second region. The wavelength of the laser light incident on the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident on the second region.

[0006] This application also provides a laser amplification device, which includes: Laser source; laser source is used to generate laser light; Dispersion element; a dispersion element is used to spatially disperse laser light incident from a laser source, so that different wavelength components of the laser light are spatially separated along a first direction; Gain crystal; The gain crystal is placed in the optical path of the laser after dispersion by the dispersive element to amplify the dispersed laser. The gain crystal is doped with activating ions. Pump source; The pump source is used to output pump light and emit it to the gain crystal, providing pump energy for the gain crystal to amplify the laser; Along the first direction, the gain crystal has a first region and a second region. The laser light dispersed by the dispersive element is incident on the first region and the second region. The wavelength of the laser light incident on the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident on the second region. Pump light is incident on a first region and a second region, and the intensity of the pump light in the first region is lower than that in the second region.

[0007] The beneficial effects of the laser amplification device provided in this application are as follows: The laser amplification device in this application, by incidenting the laser light, after spatial dispersion by a dispersive element, onto a first region and a second region of a gain crystal, ensures that the wavelength of the laser light incident on the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident on the second region. That is, the wavelength of the laser light incident on the second region is farther from the gain peak wavelength than that in the first region. Therefore, when the gain crystal amplifies the laser light, the second region is more easily weakened due to insufficient gain compared to the first region, resulting in spectral narrowing. In the laser amplification device of this application embodiment, the active ion doping concentration in the first region is lower than that in the second region. Thus, for laser components close to the gain peak wavelength, their intrinsic gain is high, but the activation ion doping concentration in the first region is low, the number of activation ions in the gain crystal that can provide gain is relatively small, the inversion particle number density is low, the gain coefficient is suppressed, and the amplification is suppressed. In the second region, the activation ion doping concentration is high, the number of activation ions in the gain crystal that can provide gain is relatively large, the inversion particle number density is high, the gain coefficient is improved, and the amplification is enhanced. This balances the gain of each wavelength component to a certain extent, reduces the gain difference of each wavelength component in the laser amplified by the gain crystal, and thus suppresses the gain narrowing effect during the amplification process, maintains the spectral width of the amplified laser, and provides favorable conditions for subsequent compression to obtain narrow pulse width femtosecond lasers. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application, 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.

[0009] Figure 1 This is a block diagram of the overall structure of the laser amplification device in one embodiment of this application; Figure 2 This is a schematic diagram of laser light incident on a gain crystal with varying doping concentration in an embodiment of this application; Figure 3 This is a schematic diagram of the gain crystal region division in one embodiment of this application; Figure 4 This is a schematic diagram of the gain crystal dividing the region in another embodiment of this application; Figure 5 This is a schematic diagram of laser light incident on a gain crystal with uniform doping concentration in an embodiment of this application; Figure 6 This is a general structural block diagram of a laser amplification device in another embodiment of this application; Figure 7 This is a schematic diagram of the pump light incident gain crystal in one embodiment of this application; Figure 8 This is a schematic diagram of the pump light incident gain crystal in another embodiment of this application; Figure 9 This is a schematic diagram showing the spatial distribution of laser and doping concentration in one embodiment of this application; Figure 10 This is a general structural block diagram of the laser amplification device in another embodiment of this application; Figure 11 This is a schematic diagram of the specific optical path structure of the laser amplification device in the embodiments of this application; Figure 12 This is a laser spectrum amplified using a related technical method; Figure 13 This is a laser spectrum amplified using another related technique; Figure 14 This is a laser spectrum amplified using the laser amplification device described in the embodiments of this application.

[0010] The following are the labeling elements in the figure: Laser source 100; dispersive element 200; gain crystal 300; first region 301; first sub-region 3011; second sub-region 3012; third sub-region 3013; second region 302; pump source 400; pump light middle region 401; pump light edge region 402; first pump light edge region 4021; second pump light edge region 4022; first pump assembly 410; first pump light 411; second pump assembly 420; second pump light 421; first pump light shaping element 430; second pump light shaping element 440; dispersed laser 500; laser middle region 501; laser edge region 502; laser shaping element 600; seed Sub-source 1; Stretcher 2; Fiber amplifier 3; Filter 4; Diffraction grating 5; First climbing mirror 6; First corner mirror 7; Focusing lens 8; Half-wave plate 9; Polarizing beam splitter 10; First dichroic mirror 11; Bonding crystal 12; Second dichroic mirror 13; Quarter-wave plate 14; Concave mirror 15; First pump source 16; First pump collimating lens 17; First pump pre-shaping cylindrical lens 18; First pump post-shaping cylindrical lens 19; Second pump source 20; Second pump collimating lens 21; Second pump pre-shaping cylindrical lens 22; Second pump post-shaping cylindrical lens 23; Collimating lens 24; Compression grating 25; Second climbing mirror 26; Second corner mirror 27; First direction a. Detailed Implementation

[0011] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0012] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0013] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. 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. Therefore, they should not be construed as limitations on this application.

[0014] 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 one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0015] Femtosecond lasers, with their ultra-high peak power and ultra-short pulse duration, represent a significant direction in laser technology development. Their pulse duration is on the order of femtoseconds, or 10^6 seconds. -15 Femtosecond lasers can concentrate and release energy in an extremely short time, resulting in extremely high peak power. This characteristic gives femtosecond lasers significant advantages in fields such as brittle material processing, high-order harmonic generation, nonlinear frequency conversion light sources, precision micro-nano fabrication, biomedicine, and time-resolved spectroscopy. In materials processing, the extremely short pulse duration of femtosecond lasers results in a minimal heat-affected zone, high processing precision, and good edge quality, enabling cold processing effects that are difficult to achieve with traditional long-pulse lasers. In nonlinear optics, the high peak power of femtosecond lasers is beneficial for driving the generation of high-order harmonics, thereby obtaining coherent light sources in the extreme ultraviolet and even soft X-ray bands. In ultrafast science, femtosecond lasers can serve as probes for time-resolved measurements and the study of ultrafast phenomena, with their time resolution directly determined by the pulse width.

[0016] The narrower the pulse width of a femtosecond laser, the better it is for achieving the aforementioned application effects. A shorter pulse width means a shorter interaction time between the laser and the material, resulting in a weaker thermal diffusion effect. This effectively reduces thermal damage and improves processing accuracy and edge quality. Furthermore, the pulse width of a femtosecond laser also determines its temporal resolution in fields such as time-resolved measurements and ultrafast phenomenon research. Therefore, obtaining a narrower femtosecond laser pulse width is an important direction for improving the application performance of femtosecond lasers.

[0017] According to the Fourier transform limit, the temporal width of a laser pulse is inversely proportional to its spectral width. For a given spectral shape, the wider the laser spectrum, the narrower the theoretically achievable laser pulse width. Taking a Gaussian spectrum as an example, the laser pulse width and spectral width satisfy the time-bandwidth product relationship; under the transform limit condition, the laser pulse width equals the time-bandwidth product constant divided by the spectral width. Therefore, obtaining a wide spectral output is a crucial prerequisite for realizing narrow-pulse-width femtosecond lasers. In other words, to further compress the pulse width of a femtosecond laser, it is essential to first ensure that the femtosecond laser has a sufficiently wide spectral width.

[0018] However, during laser amplification, the gain medium exhibits varying gain capabilities for different wavelength components. Typically, a gain medium possesses a specific gain spectrum, with the stimulated emission cross-section at the gain peak wavelength being the largest and the gain coefficient highest, while spectral components farther from the gain peak wavelength have lower gain coefficients. When a broadband laser pulse is amplified through a gain medium, the spectral components near the gain peak wavelength are amplified significantly more than those on either side. After multiple stages or passes of amplification, this difference accumulates, resulting in the output laser's spectral width being significantly smaller than the input laser's spectral width—a gain narrowing effect. This gain narrowing effect disrupts the broadband characteristics, limiting further reduction in the width of the compressed femtosecond laser pulse, making it difficult to meet the demands of high-precision machining and other applications requiring narrow-pulse-width femtosecond lasers.

[0019] Taking Yb:YAG crystal as an example, Yb:YAG crystal, also known as yttrium aluminum garnet crystal, has a broad emission spectrum of approximately 9 nm, making it suitable as a gain medium for femtosecond laser amplifiers. However, in actual amplification, due to the gain narrowing effect, the output laser spectral width of the amplifier using this crystal as the gain medium is typically only about 2 nm, resulting in a compressed femtosecond laser pulse width of approximately 700 femtoseconds. This pulse width is significantly larger than the transform-limited pulse width theoretically supported by the 9 nm emission spectrum, indicating that the gain narrowing effect severely restricts the narrow pulse width output of femtosecond lasers.

[0020] To suppress gain narrowing, some techniques typically employ spectral shaping to pre-compensate the seed pulse spectrum. This involves pre-lowering the spectral energy near the gain peak wavelength to compensate for gain differences during amplification, ensuring that the spectral components are more balanced after amplification. However, traditional spectral shaping methods struggle to accurately match the gain curve of the gain medium, resulting in limited compensation accuracy and incomplete narrowing suppression. Consequently, spectral narrowing and a wide pulse width persist after amplification. Furthermore, while adding a nonlinear broadening and re-compression module after the compressor can further compress the femtosecond laser pulse width, the high single-pulse energy significantly reduces the stability and reliability of subsequent modules. Additionally, the system becomes complex, costly, and prone to material damage.

[0021] Therefore, how to effectively suppress the gain narrowing effect during the amplification process and obtain high-quality femtosecond laser output with a wide spectrum and narrow pulse width is a technical problem that urgently needs to be solved in this field.

[0022] To address the aforementioned problems, this application provides a laser amplification device. Please refer to [link / reference]. Figure 1 and Figure 2 The laser amplification device includes: Laser source 100; Laser source 100 is used to generate laser light; Dispersion element 200; the dispersion element 200 is used to spatially disperse the laser incident from the laser source 100, so that different wavelength components of the laser are spatially separated along the first direction a. Gain crystal 300; The gain crystal 300 is placed in the optical path of the laser after dispersion by the dispersive element 200, and is used to amplify the dispersed laser. The gain crystal 300 is doped with activating ions. Pump source 400; Pump source 400 is used to output pump light and emit it to gain crystal 300, providing pump energy for gain crystal 300 to amplify laser; Along the first direction a, the gain crystal 300 has a first region 301 and a second region 302, wherein the doping concentration of active ions in the first region 301 is lower than the doping concentration of active ions in the second region 302. The laser light dispersed by the dispersing element 200 is incident on the first region 301 and the second region 302, and the wavelength of the laser light incident on the first region 301 is closer to the gain peak wavelength of the gain crystal 300 than the wavelength of the laser light incident on the second region 302.

[0023] In this embodiment, the laser source 100 is used to generate laser light. The laser source 100 can be a commonly used light source in the art capable of generating femtosecond laser pulses, such as an fiber optic oscillator or a solid-state oscillator. The laser light generated by the laser source 100 serves as the seed light for the subsequent amplification process, and its spectral width and pulse width determine the initial performance of the entire amplification system.

[0024] The dispersive element 200 is used to spatially disperse the laser light incident from the laser source 100, causing different wavelength components of the laser to be spatially separated along a first direction a. Spatial dispersion refers to separating different wavelength components of the laser in space, with different wavelengths of laser light illuminating different spatial locations along the first direction a. The dispersive element 200 can be a transmission diffraction grating, a reflection diffraction grating, a prism, or other optical elements with spatial dispersion capabilities. After passing through the dispersive element 200, the laser spot expands in space, forming a spectral pattern with a continuous wavelength distribution along the first direction a. The first direction a is the direction in which the wavelengths of the laser are separated after dispersion by the dispersive element 200, that is, the direction in which different wavelength components are arranged sequentially in space, and is usually perpendicular to the direction of laser propagation. It should be noted that the first direction a is not a fixed direction, but is determined by the type of dispersive element 200, its placement angle, and the direction of laser incident. For example, when the dispersive element 200 is a transmission diffraction grating, the first direction a is the diffraction direction of the grating; when the dispersive element 200 is a prism, the first direction a is the dispersion direction of the prism. The laser light dispersed by the dispersive element 200 has different wavelength components at different positions along the first direction a, and the wavelength changes continuously along the first direction a, forming a spatial wavelength mapping relationship.

[0025] A gain crystal 300 is positioned in the optical path of the laser beam dispersed by the dispersive element 200 to amplify the dispersed laser. The gain crystal 300 is an optical crystal doped with active ions, capable of providing gain to the signal laser under pump light excitation. Active ions are ions that provide laser gain under pump light excitation, such as ytterbium ions, neodymium ions, and erbium ions. The gain crystal 300 can be a Yb:YAG crystal, i.e., a ytterbium-doped yttrium aluminum garnet crystal. A Yb:YAG crystal is a gain crystal 300 with yttrium aluminum garnet as the matrix and ytterbium ions as the active ions. The active ion doping concentration of the gain crystal 300 varies along the first direction a. Doping concentration refers to the number or atomic percentage of active ions incorporated per unit volume in the gain crystal 300; a higher doping concentration provides a higher gain under the same pumping conditions.

[0026] Along the first direction a, the gain crystal 300 has a first region 301 and a second region 302, which are two different doping concentration regions divided along the first direction a in the gain crystal 300. Laser light dispersed by the dispersive element 200 is incident on the first region 301 and the second region 302, and the wavelength of the laser light incident on the first region 301 is closer to the gain peak wavelength of the gain crystal 300 than the wavelength of the laser light incident on the second region 302. The gain peak wavelength refers to the wavelength with the largest stimulated emission cross-section and the highest gain coefficient in the gain crystal 300. The stimulated emission cross-section refers to the probability of an activated ion undergoing a stimulated emission transition at a specific wavelength; a larger stimulated emission cross-section indicates that stimulated emission amplification is more likely to occur at that wavelength. Since the laser wavelength incident on the second region 302 is farther from the gain peak wavelength than that of the first region 301, when the gain crystal 300 amplifies the laser light, the second region 302 is more likely to be weakened due to insufficient gain, resulting in spectral narrowing, compared to the first region 301. In this embodiment, the doping concentration of active ions in the first region 301 is lower than that in the second region 302. Taking a Yb:YAG crystal as an example, the peak gain wavelength is typically around 1030 nm. That is, after dispersion by the dispersant 200, the laser component with a wavelength relatively close to 1030 nm is incident on the first region 301 with a lower doping concentration, while the laser component with a wavelength relatively far from 1030 nm is incident on the second region 302 with a higher doping concentration.

[0027] The reason for this configuration is that the gain crystal 300 has different gain capabilities for different wavelength components. Laser components near the gain peak wavelength have a higher gain coefficient in the gain crystal 300, and can obtain sufficient gain amplification even with a low doping concentration; while laser components far from the gain peak wavelength have a lower gain coefficient in the gain crystal 300, requiring a higher doping concentration to compensate for their insufficient gain. The gain coefficient refers to the relative increase in light intensity after propagating a unit distance in the gain medium, reflecting the amplification capability of the gain medium.

[0028] By incident laser components close to the gain peak wavelength into a low-doped region and laser components far from the gain peak wavelength into a high-doped region, the gain of different wavelength components during the amplification process can be made more balanced, thereby effectively suppressing the gain narrowing effect and maintaining the spectral width of the amplified laser.

[0029] The effect of doping concentration on gain can be understood from the relationship between the gain coefficient and the stimulated emission cross section and the inverted particle number density. The gain coefficient is equal to the product of the stimulated emission cross section and the inverted particle number density. The inverted particle number density refers to the difference in the number of particles in the upper energy level and the number of particles in the lower energy level per unit volume, representing the effective number of active ions in the gain medium that can participate in stimulated emission amplification. At the gain peak wavelength, the stimulated emission cross section is the largest, and even if the inverted particle number density is low, the gain coefficient can still be maintained at a high level; while far from the gain peak wavelength, the stimulated emission cross section is small, and only by increasing the inverted particle number density can a similar gain coefficient be obtained. When there is no pump saturation or concentration quenching, the inverted particle number density is positively correlated with the active ion doping concentration and the pump energy. Therefore, by reducing the doping concentration of the first region 301, the upper limit of the achievable inverted particle number density can be limited, thereby limiting the maximum gain coefficient at the gain peak wavelength, and thus the gain at the gain peak wavelength can be suppressed in a targeted manner. Correspondingly, by increasing the doping concentration of the second region 302, the gain far from the gain peak wavelength can be enhanced. This reduces the gain difference among different wavelength components in the laser amplified by the gain crystal, thereby suppressing the gain narrowing effect during the amplification process.

[0030] The pump source 400 outputs pump light and directs it to the gain crystal 300, providing pump energy for the gain crystal 300 to amplify the laser. Pump light is the light used to excite the active ions in the gain crystal 300. Its photon energy is absorbed by the active ions, causing them to transition from a low energy level to a high energy level, thus providing energy for laser amplification. Pump energy refers to the energy carried by the pump light that can be absorbed by the gain crystal 300 and converted into laser gain. The pump source 400 can be a laser diode or other device capable of providing pump light. After the pump light is incident on the gain crystal 300, it excites the active ions in the gain crystal 300, putting them in a population inversion state. Population inversion refers to a state where the number of particles in high energy levels is greater than the number of particles in low energy levels, which is a necessary condition for laser amplification. The pump light provides energy to the gain crystal 300, exciting the active ions and thus providing gain for the signal laser.

[0031] Taking the gain crystal 300 as a Yb:YAG crystal as an example, its active ion is ytterbium ion, the laser wavelength is around 1030 nm, and the pump light wavelength is around 940 nm. After dispersion by the dispersing element 200, the laser component with a wavelength around 1030 nm is incident along the first direction a into the first region 301 of the gain crystal 300, while the laser component with a wavelength far from 1030 nm is incident into the second region 302. The doping concentration of the active ion in the first region 301 is lower than that in the second region 302. Through this matching, the strong gain near the gain peak wavelength is suppressed by low doping, while the weak gain far from the gain peak wavelength is compensated by high doping, thereby balancing the gain of each wavelength component overall, suppressing the gain narrowing effect, and obtaining a broad-spectrum laser output.

[0032] Those skilled in the art will understand that the number of first regions 301 and second regions 302 can be adjusted according to actual needs. Along the first direction a, the gain crystal 300 can have multiple first regions 301 and multiple second regions 302, as long as the laser wavelength incident on the first region 301 is closer to the gain peak wavelength than the laser wavelength incident on the second region 302, and the doping concentration of the first region 301 is lower than that of the second region 302. There may be exceptions in some regions, such as a small portion of the laser component near the gain peak wavelength being incident on the highly doped region, while the laser component slightly deviating from the gain peak wavelength is incident on the low-doped region. As long as the above correspondence is satisfied overall, the effect of suppressing gain narrowing can still be achieved.

[0033] Through the above configuration, the laser amplification device provided in this embodiment utilizes spatial dispersion to separate different wavelength components into different spatial locations, and adjusts the doping concentration at each corresponding spatial location. This helps to make the gain coefficients of each wavelength component more consistent during amplification, thereby suppressing the gain narrowing effect to a certain extent. The amplified laser spectral width is increased compared to the spectral width amplified by a traditional uniformly doped gain medium, providing a wider spectral basis for subsequent pulse compression. According to the Fourier transform limit, a wider spectrum means that a narrower pulse width can be obtained through compression. Therefore, this embodiment can at least partially alleviate the gain narrowing effect, which is beneficial to improving the narrow pulse width output capability of femtosecond lasers, thereby improving their application performance in fields such as brittle material processing, high-order harmonic generation, and nonlinear frequency conversion light sources, including processing accuracy, edge quality, and temporal resolution.

[0034] Please see Figure 2 In some embodiments of this application, the laser light dispersed by the dispersant 200 has a laser intermediate region 501 and laser edge regions 502 located on both sides of the laser intermediate region 501 along the first direction a. The wavelength of the laser light in the laser intermediate region 501 is closer to the gain peak wavelength of the gain crystal 300 than the wavelength of the laser light in the laser edge region 502. Along the first direction a, the first region 301 is located in the middle of the gain crystal 300, and the second region 302 is located on both sides of the first region 301 along the first direction a. The laser intermediate region 501 is incident on the first region 301, and the laser edge region 502 is incident on the second region 302.

[0035] After being dispersed by the dispersing element 200, the laser beam, once spread along the first direction a, has a spatial intensity distribution and wavelength distribution. In this embodiment, the laser beam dispersed by the dispersing element 200 has a central region 501 and laser edge regions 502 located on both sides of the central region 501 along the first direction a. The central region 501 and the laser edge regions 502 are regions obtained by spatially dividing the dispersed laser beam along the first direction a, wherein the central region 501 is located in the middle of the laser beam, and the laser edge regions 502 are located on both sides of the laser beam.

[0036] Since the dispersing element 200 arranges different wavelength components sequentially along the first direction a, different positions of the laser spot along the first direction a correspond to different wavelength components. Typically, the wavelength changes continuously along the first direction a, therefore the laser wavelength in the central region 501 is different from the laser wavelength in the edge region 502. In this embodiment, the laser wavelength in the central region 501 is closer to the gain peak wavelength of the gain crystal 300 than the laser wavelength in the edge region 502. That is, after dispersion by the dispersing element 200, wavelength components close to the gain peak wavelength are mainly distributed in the central region of the laser spot, while wavelength components far from the gain peak wavelength are mainly distributed on both sides of the laser spot. For example, when the gain crystal 300 is a Yb:YAG crystal, the gain peak wavelength is around 1030nm, the laser wavelength in the central region 501 is around 1030nm, while the laser wavelength in the edge region 502 deviates significantly from 1030nm, for example, spreading towards shorter and longer wavelengths respectively.

[0037] It should be noted that the spatial distribution of the laser intermediate region 501, with its wavelength closer to the gain peak wavelength, matches common spectral shapes. For example, when the laser output from the laser source 100 has a Gaussian spectrum, the spectral intensity follows a Gaussian distribution, and the gain peak wavelength is typically located at or near the center of the spectrum. After dispersion by the dispersive element 200, the laser intermediate region 501 corresponds to the center wavelength, naturally being closer to the gain peak wavelength. Similar spatial distribution characteristics exist for other spectral shapes with center wavelengths close to the gain peak wavelength. Therefore, the limitations of this embodiment can match the physical characteristics of common spectral shapes, ensuring that the laser intermediate region 501 primarily corresponds to wavelength components with higher intrinsic gain.

[0038] Along the first direction a, the first region 301 of the gain crystal 300 is located in the middle of the gain crystal 300, and the second region 302 is located on both sides of the first region 301 along the first direction a. That is, the low-doped region of the gain crystal 300 is located in the middle, and the high-doped region is located on both sides, forming a spatial distribution of low doping in the middle and high doping on both sides. This distribution matches the wavelength distribution of the dispersed laser spot: the laser middle region 501 corresponds to the middle of the gain crystal 300, i.e., the first region 301; the laser edge region 502 corresponds to both sides of the gain crystal 300, i.e., the second region 302.

[0039] In this embodiment, the laser's central region 501 is incident on the first region 301 of the gain crystal 300, and the laser's edge region 502 is incident on the second region 302 of the gain crystal 300. Thus, laser components with wavelengths close to the gain peak wavelength are incident on the first region 301 with a lower doping concentration, while laser components with wavelengths far from the gain peak wavelength are incident on the second region 302 with a higher doping concentration. This arrangement is because laser components near the gain peak wavelength have higher intrinsic gain and can still achieve sufficient amplification under low doping conditions; while laser components far from the gain peak wavelength have lower intrinsic gain and require a higher doping concentration to enhance amplification. Through this spatial matching relationship, differential compensation can be performed for the gain differences of different wavelength components, making the gain of each wavelength component tend to be balanced during the amplification process, thereby suppressing the gain narrowing effect to a certain extent and helping to maintain the spectral width of the amplified laser.

[0040] It should be noted that the laser intermediate region 501 and the laser edge region 502 are not required to have strict geometric symmetry, nor are they required that the laser intermediate region 501 exactly corresponds to the first region 301 and the laser edge region 502 exactly corresponds to the second region 302. It is sufficient that the wavelength of the laser intermediate region 501 is closer to the gain peak wavelength than the wavelength of the laser edge region 502, and that the laser intermediate region 501 is mainly incident on the first region 301 and the laser edge region 502 is mainly incident on the second region 302. A transition region may exist between the first region 301 and the second region 302, and the laser spot may also have a spatially continuous transition; this embodiment does not impose strict limitations on this.

[0041] With the above settings, the spatial distribution of wavelengths formed after dispersion corresponds to the spatial distribution of doping concentration in the gain crystal 300. This results in the suppression of strong gain components near the gain peak wavelength by low doping and the compensation of weak gain components far from the gain peak wavelength by high doping. This helps to improve the spectral narrowing phenomenon during amplification and provides a structural basis for obtaining femtosecond laser output with a wide spectrum and narrow pulse width.

[0042] Please see Figure 2 , Figure 3 and Figure 4 In some embodiments of this application, the gain crystal 300 includes a plurality of crystal segments arranged sequentially along a first direction a, and the activation ion doping concentrations of adjacent crystal segments are different; the first region 301 includes at least one crystal segment located in the middle of the gain crystal 300, and the second region 302 includes at least one crystal segment located on both sides of the first region 301 along the first direction a.

[0043] In this embodiment, the gain crystal 300 may include multiple crystal segments arranged sequentially along the first direction a, with adjacent crystal segments having different activation ion doping concentrations. A crystal segment refers to a section of the gain crystal 300 with a specific doping concentration divided along the first direction a. Multiple crystal segments are arranged sequentially along the first direction a, forming a structure where the doping concentration varies spatially in segments. The doping concentration of adjacent crystal segments differs, meaning the doping concentration of the gain crystal 300 varies in a stepwise manner along the first direction a, rather than being uniformly distributed.

[0044] In the plurality of crystal segments, the first region 301 includes at least one crystal segment located in the middle of the gain crystal 300, and the second region 302 includes at least one crystal segment located on both sides of the first region 301 along the first direction a. Because the doping concentration of active ions in the first region 301 is lower than the doping concentration of active ions in the second region 302, the doping concentration of active ions in the crystal segment located in the first region 301 is lower than the doping concentration of active ions in the crystal segment located in the second region 302.

[0045] The specific number and arrangement of crystal segments can be flexibly set according to actual needs. For example, Figure 2 As shown, the gain crystal 300 may include three crystal segments, wherein a crystal segment located in the middle forms a first region 301, and two crystal segments located on both sides respectively form second regions 302, each second region 302 consisting of one crystal segment. Figure 3 As shown, the gain crystal 300 may include five crystal segments, wherein the three crystal segments located in the middle together form a first region 301, and the two crystal segments located on both sides respectively form a second region 302, each second region 302 being composed of one crystal segment. Figure 4 As shown, the gain crystal 300 may also include five crystal segments, with one crystal segment in the middle forming a first region 301, and four crystal segments on both sides forming two second regions 302, each of which consists of two crystal segments. In addition, the gain crystal 300 may be configured with more or fewer crystal segments as needed. The number of crystal segments contained in the first region 301 and the second region 302 is not limited to the example above, as long as the doping concentration of the active ions in the first region 301 is lower than the doping concentration of the active ions in the second region 302.

[0046] The crystal segments can be connected to form a whole through bonding. That is, the gain crystal 300 is a bonded crystal, composed of multiple crystal segments with different doping concentrations bonded along the first direction a. The bonded crystal can combine crystal segments with different doping concentrations into a complete gain crystal 300 without changing the doping concentration of each segment, allowing the laser to obtain different gains when passing through each crystal segment. There can be a transition region or a clear interface between adjacent crystal segments; this embodiment does not impose strict limitations on this. The activation ion doping concentration of adjacent crystal segments can vary sequentially according to a preset concentration value. For example, the doping concentration can gradually increase from the middle to both sides, or a certain concentration difference can be maintained between adjacent crystal segments, without requiring a strictly symmetrical concentration distribution.

[0047] Besides the segmented arrangement mentioned above, the doping concentration of the active ions in the gain crystal 300 can also be achieved by a continuous gradient along the first direction a. For example, by controlling the doping concentration to continuously vary along the first direction a through the crystal growth process, the doping concentration in the middle of the gain crystal 300 can be low, while the doping concentration on both sides can be high, forming a smooth concentration distribution. The continuous gradient method can also form a spatial doping distribution with low concentration in the middle and high concentration on both sides, matching the wavelength spatial distribution of the laser. This suppresses the amplification of laser components near the gain peak wavelength in the low-doped region, while compensating for laser components far from the gain peak wavelength in the high-doped region. The gain of each wavelength component tends to be balanced, which is beneficial for maintaining the spectral width of the amplified laser.

[0048] Both segmented arrangement and continuous gradient methods have their own advantages. The segmented arrangement method has a relatively simple fabrication process, high precision in controlling doping concentration, and allows for flexible setting of concentration values ​​in different regions according to actual needs. The continuous gradient method, on the other hand, does not have a clear concentration interface in space, which helps to reduce the adverse effects that may be introduced by abrupt changes in concentration when the laser propagates in the gain crystal 300. Those skilled in the art can choose a suitable doping concentration distribution method according to actual needs.

[0049] Please see Figure 2 In some embodiments of this application, pump light is incident on a first region 301 and a second region 302, and the intensity of the pump light in the first region 301 is lower than the intensity in the second region 302.

[0050] Pump light output from pump source 400 is incident on the first region 301 and the second region 302 of gain crystal 300, providing energy to the activated ions in gain crystal 300. After the pump light is incident on gain crystal 300, it excites the activated ions to transition from low energy levels to high energy levels, resulting in more particles in high energy levels than in low energy levels, forming population inversion, thereby providing gain for the signal laser. In this embodiment, the intensity of the pump light in the first region 301 is lower than that in the second region 302. Pump light intensity refers to the power of the pump light per unit area. The higher the pump light intensity, the more activated ions are excited to high energy levels per unit volume, the higher the population inversion density, and the higher the gain coefficient of gain crystal 300. The fact that the intensity of the pump light in the first region 301 is lower than that in the second region 302 means that the gain coefficient of the first region 301 is lower than that of the second region 302.

[0051] It should be noted that, as Figure 5 As shown, this differentiated pump intensity setting can function independently even when the doping concentration of the gain crystal 300 is uniform. The gain narrowing effect arises essentially from the difference in intrinsic gain between different wavelength components. Laser components near the gain peak wavelength have a large stimulated emission cross-section and a high gain coefficient, while laser components far from the gain peak wavelength have a small stimulated emission cross-section and a low gain coefficient. Even if the doping concentration of the gain crystal 300 is uniform everywhere, as long as the pump intensity varies at different spatial locations, the inversion particle number density will differ at different spatial locations, and the gain coefficient will also differ accordingly. Therefore, based on the correspondence between the distribution of different wavelength components along the first direction a at different spatial locations after dispersion, by adjusting the spatial distribution of the pump intensity accordingly—corresponding to laser components near the gain peak wavelength in areas with lower pump intensity and laser components far from the gain peak wavelength in areas with higher pump intensity—the gain narrowing effect can also be suppressed. This corresponds to an independent scheme in the embodiments of this application, where the doping concentration of the gain crystal 300 remains unchanged, and spectral narrowing suppression is achieved solely through spatial differentiation of the pump intensity.

[0052] Building upon this, combining the differences in doping concentration with the differences in pump intensity allows them to work together to form a third scheme. Doping concentration determines the spatial distribution density of active ions, while pump intensity determines the proportion of active ions excited to higher energy levels. Together, they determine the inversion particle number density, which in turn determines the gain coefficient. When the doping concentration of the first region 301 is lower than that of the second region 302, and the pump light intensity in the first region 301 is also lower than that in the second region 302, the inversion particle number density in the first region 301 is further lower than that in the second region 302 under the combined effect of doping concentration and pump intensity. This results in a greater difference in the gain coefficient between the first and second regions 301, leading to a more significant compensation effect. This combined scheme offers a wider adjustment range and stronger narrowing suppression capability compared to individually controlling either the doping concentration or the pump intensity.

[0053] Specifically, the first region 301 is used to receive laser components with wavelengths closer to the gain peak wavelength. These laser components have high intrinsic gain in the gain crystal 300, and the pump light intensity in the first region 301 is low to avoid over-amplification of these wavelength components. The second region 302 is used to receive laser components with wavelengths further away from the gain peak wavelength. These laser components have low intrinsic gain in the gain crystal 300, and the pump light intensity in the second region 302 is high to enhance the amplification of these wavelength components. By differentiating the pump intensity, the gain difference between different wavelength components can be reduced, making the gain of each wavelength component tend to be more balanced during the amplification process, which helps to alleviate the gain narrowing effect.

[0054] It should be noted that the distribution of pump intensity in the first region 301 and the second region 302 is not required to have strict boundaries, nor is it required that the pump intensity in the first region 301 be the same everywhere, or that the pump intensity in the second region 302 be the same everywhere. The pump light can have a spatially continuous transition within the gain crystal 300, as long as the overall intensity of the pump light in the first region 301 is lower than that in the second region 302.

[0055] Taking the gain crystal 300 as a Yb:YAG crystal as an example, the gain peak wavelength is around 1030nm. The laser wavelength incident on the first region 301 is also around 1030nm, resulting in a high intrinsic gain. Therefore, the pump light intensity in the first region 301 is low to prevent over-amplification of this wavelength component. Conversely, the laser wavelength incident on the second region 302 deviates significantly from 1030nm, resulting in a lower intrinsic gain. Therefore, the pump light intensity in the second region 302 is high, enhancing the amplification of this wavelength component. This configuration suppresses strong gain components near the gain peak wavelength with low pump intensity, while compensates for weak gain components far from the gain peak wavelength with high pump intensity. This balances the gain across wavelength components, which is beneficial for obtaining a broad-spectrum laser output.

[0056] In summary, suppressing the gain narrowing effect can be achieved through three approaches: adjusting the doping concentration alone, adjusting the pump intensity alone, and adjusting both the doping concentration and pump intensity simultaneously. Adjusting the doping concentration alone compensates for gain differences by spatially adjusting the distribution density of activated ions; adjusting the pump intensity alone compensates for gain differences by spatially adjusting the excitation level of activated ions; and adjusting both simultaneously combines the two methods, allowing for flexible adjustment of the gain of each wavelength component over a wider range, resulting in better spectral preservation. Those skilled in the art can choose the appropriate approach based on actual application requirements and process conditions.

[0057] Please see Figure 6 , Figure 7 and Figure 8 In some embodiments of this application, the pump light source 400 includes a first pump component 410 for outputting a first pump light 411 and a second pump component 420 for outputting a second pump light 421. The pump light output by the first pump component 410 and the second pump component 420 both have a pump light middle region 401 and pump light edge regions 402 located on both sides of the pump light middle region 401. The intensity of the pump light middle region 401 is higher than the intensity of the pump light edge regions 402. The first pump light 411 is incident on one side of the gain crystal 300 along the first direction a, and the second pump light 421 is incident on the other side of the gain crystal 300 along the first direction. The edge region 4021 of the first pump light and the edge region 4022 of the second pump light are incident on the first region 301. The first pump light edge region 4021 is the pump light edge region 402 of the first pump light 411 that is close to the side of the second pump light 421. The second pump light edge region 4022 is the pump light edge region 402 of the second pump light 421 that is close to the side of the first pump light 411. The middle region 401 of the first pump light 411 is incident on the second region 302 on one side of the gain crystal 300, and the middle region 401 of the second pump light 421 is incident on the second region 302 on the other side of the gain crystal 300.

[0058] The first pump light 411 and the second pump light 421 are incident on the gain crystal 300 from both sides along the first direction a, and the pump light edge regions 402 of the first pump light 411 and the second pump light 421 are incident on the first region 301, and the pump light middle regions 401 of the first pump light 411 and the second pump light 421 are incident on the second regions 302 on both sides.

[0059] The pump source 400 includes a first pump component 410 and a second pump component 420. The first pump component 410 outputs a first pump light 411, and the second pump component 420 outputs a second pump light 421. Both the first pump light 411 and the second pump light 421 have a central pump light region 401 and edge pump light regions 402 located on both sides of the central pump light region 401. The intensity of the central pump light region 401 is higher than that of the edge pump light region 402. The central pump light region 401 refers to the central part of the pump light spot with higher intensity, and the edge pump light region 402 refers to the peripheral part of the pump light spot with lower intensity. For common pump sources 400 such as laser diodes, their output beams typically exhibit a spatial distribution characteristic of strong intensity at the center and weak intensity at the edges. This distribution can also be obtained by spatially shaping the pump light.

[0060] The first pump light 411 is incident on one side of the gain crystal 300 along the first direction a, and the second pump light 421 is incident on the other side of the gain crystal 300 along the first direction a. Both the first pump light 411 and the second pump light 421 have a pump light central region 401 and pump light edge regions 402 located on both sides of the pump light central region 401. The intensity of the pump light central region 401 is higher than the intensity of the pump light edge regions 402, that is, each pump light beam has a spatial intensity distribution that is strong in the middle and weak at the edges.

[0061] For the first pump light 411, its central region 401 illuminates the second region 302 on one side of the gain crystal 300, providing a higher pump intensity for the laser component far from the gain peak wavelength; the portion of its pump light edge region 402 near the second pump light 421, i.e., the first pump light edge region 4021, illuminates the first region 301 in the middle of the gain crystal 300. For the second pump light 421, its central region 401 illuminates the second region 302 on the other side of the gain crystal 300; the portion of its pump light edge region 402 near the first pump light 411, the second pump light edge region 4022, illuminates the first region 301 in the middle of the gain crystal 300.

[0062] Therefore, the two second regions 302 on both sides of the gain crystal 300 receive the pump light from the middle region 401 of the first pump light 411 and the second pump light 421, respectively, that is, they receive pump light with higher intensity; the first region 301 in the middle of the gain crystal 300 simultaneously receives the pump light from the edge region 402 of the first pump light 411 and the second pump light 421, that is, it receives pump light with lower intensity. In this way, a spatial distribution with low pump intensity in the first region 301 and high pump intensity in the second region 302 is formed within the gain crystal 300.

[0063] It should be noted that this spatial distribution setting of pump intensity can be effective in both embodiments.

[0064] like Figure 7 As shown, in one embodiment, the gain crystal 300 itself has a doping concentration varying along a first direction a, with the activation ion doping concentration of the first region 301 being lower than that of the second region 302. In this case, the spatial distribution of the pump intensity is consistent with the spatial distribution of the doping concentration; the first region 301 has a low doping concentration and low pump intensity, while the second region 302 has a high doping concentration and high pump intensity. The first region 301 receives laser components close to the gain peak wavelength, which have high intrinsic gain. Under the combined effect of low doping and low pumping, the amplification is suppressed. The second region 302 receives laser components far from the gain peak wavelength, which have low intrinsic gain. Under the combined effect of high doping and high pumping, the amplification is enhanced. The combined effect of doping concentration and pump intensity makes the gain difference between the first region 301 and the second region 302 more significant, enabling adjustment of the gain of each wavelength component over a wider range and achieving better narrowing suppression.

[0065] like Figure 8 As shown, in another embodiment, the doping concentration of the gain crystal 300 can be uniform and does not change with spatial position. In this case, gain control can be achieved solely through the spatial distribution of the pump intensity. The first region 301 receives a low pump intensity, resulting in a low proportion of active ions being excited to high energy levels, a low inversion particle number density, and a low gain coefficient; the second region 302 receives a high pump intensity, resulting in a high proportion of active ions being excited to high energy levels, a high inversion particle number density, and a high gain coefficient. By incident laser components near the gain peak wavelength into the first region 301 with lower pump intensity and laser components far from the gain peak wavelength into the second region 302 with higher pump intensity, the problem of excessively high gain near the gain peak wavelength can be suppressed, and the gain far from the gain peak wavelength can be enhanced, making the gain of each wavelength component more balanced and alleviating the gain narrowing effect.

[0066] In other words, the pump structure provided in the above embodiments can be used in conjunction with the doping concentration variation scheme described above, or it can be used independently as a gain control method to function alone in the gain crystal 300 with uniform doping concentration. Those skilled in the art can choose a suitable implementation method according to actual application needs and process conditions.

[0067] It should be noted that the intermediate region 401 and the edge region 402 of the first pump light 411 and the second pump light 421 are not required to have strict spatial boundaries, nor are the intensity of the intermediate region 401 and the edge region 402 required to be the same everywhere. The pump light can have a continuous intensity transition in space, as long as the overall intensity of the intermediate region 401 is higher than that of the edge region 402, and the intermediate region 401 mainly illuminates the second region 302, while the edge region 402 mainly illuminates the first region 301.

[0068] Furthermore, the pump light edge regions 402 of the first pump light 411 and the second pump light 421 can overlap in the first region 301. Different degrees of overlap result in different pump intensities actually received by the first region 301. When it is necessary to moderately enhance the pump intensity of the first region 301, the degree of overlap of the two pump light edge regions 402 in the first region 301 can be increased; when it is necessary to further suppress the gain of the first region 301, the degree of overlap can be decreased. By adjusting the relative position or spatial intensity distribution of the two pump lights, the pump intensity difference between the first region 301 and the second region 302 can be flexibly controlled to match the gain narrowing degree under different gain crystals 300 and different spectral distribution conditions.

[0069] like Figure 7 and Figure 8 As shown, in some embodiments, the first pump light 411 and the second pump light 421 are incident from two opposite sides of the gain crystal 300 in a direction perpendicular to the first direction a.

[0070] Taking the first direction 'a' as the vertical direction as an example, the laser light dispersed by the dispersant 200 spreads vertically, and the first region 301 and the second region 302 of the gain crystal 300 are distributed vertically. The first pump light 411 can enter from the left side of the gain crystal 300, and the second pump light 421 can enter from the right side. In this incident mode, the propagation directions of the first pump light 411 and the second pump light 421 within the gain crystal 300 are perpendicular to the first direction 'a'. The first pump light 411 enters from the left side of the gain crystal 300, and the second pump light 421 enters from the right side, with the two pump lights entering the gain crystal 300 in opposite directions horizontally. The propagation path length of the pump light within the gain crystal 300 is determined by the horizontal dimensions of the gain crystal 300. During propagation, the pump light is gradually absorbed by activated ions, transferring energy to the gain crystal 300 and providing gain for the signal laser.

[0071] This symmetrical incident arrangement positions the two pump light sources 400 on opposite sides of the gain crystal 300, rather than concentrating them on the same side. The pump optical path and the signal laser optical path are spatially separated, reducing mutual interference between them. Furthermore, because the two pump light sources 400 are located on opposite sides, thermal effects and optical feedback between them are less likely to interfere with each other, thus improving the anti-interference capability and stability of the pump system.

[0072] It should be noted that regardless of whether the first pump light 411 and the second pump light 421 are incident from both sides along the first direction a or from two opposite sides perpendicular to the first direction a, the desired pump spatial distribution in which the pump intensity of the first region 301 is lower than that of the second region 302 can be obtained through appropriate beam shaping and position adjustment. The specific incident method can be determined based on the shape, size, doping distribution of the gain crystal 300 and the overall optical path structure, and this embodiment does not impose strict limitations on this.

[0073] Please see Figure 2 In some embodiments of this application, the intensity of the laser after dispersion by the dispersing element 200 varies along the first direction a, and the intensity of the laser incident on the first region 301 is higher than the intensity of the laser incident on the second region 302.

[0074] The laser beam dispersed by the dispersive element 200 exhibits not only wavelength separation but also intensity distribution along the first direction a. After the laser spot expands in space, different spatial positions correspond to different wavelength components, and the intensities of each wavelength component may also differ. In this embodiment, the intensity of the laser beam dispersed by the dispersive element 200 varies along the first direction a, and the intensity of the laser incident on the first region 301 is higher than the intensity of the laser incident on the second region 302.

[0075] For common Gaussian spectral lasers, the spectral intensity is higher near the gain peak wavelength and lower further away. After dispersion by the dispersive element 200, the wavelength components near the gain peak wavelength correspond to the central region of the laser spot, with higher intensity; the wavelength components far from the gain peak wavelength correspond to the edge region of the laser spot, with lower intensity. Therefore, the laser intensity incident on the first region 301 is higher than the laser intensity incident on the second region 302, and this intensity distribution corresponds to the wavelength spatial distribution.

[0076] This intensity distribution, combined with the intrinsic gain characteristics of the gain crystal 300, will further exacerbate spectral narrowing if left uncontrolled. Laser components near the gain peak wavelength have inherently high intensity and intrinsic gain, resulting in a greater increase in intensity after amplification; conversely, laser components far from the gain peak wavelength have inherently low intensity and intrinsic gain, leading to a smaller increase in intensity after amplification. Consequently, the gap between high-intensity and low-intensity components in the amplified spectrum is further widened, making spectral narrowing more pronounced.

[0077] In this embodiment, the laser intensity incident on the first region 301 is higher than that incident on the second region 302, while the activation ion doping concentration in the first region 301 is lower than that in the second region 302, and the gain is also lower in the first region 301. Therefore, the higher-intensity laser component enters the lower-gain region, and the amplification is suppressed; the lower-intensity laser component enters the higher-gain region, and the amplification is enhanced. This arrangement, to a certain extent, compensates for the amplification imbalance caused by differences in intrinsic gain and initial intensity between different wavelength components, preventing the intensity ratio of each wavelength component from being excessively stretched after amplification, and maintaining the spectral width relatively well.

[0078] In principle, the first region 301 has a low doping concentration, low inverted particle number density, and low gain coefficient. Although the incident laser intensity is high, the amplification factor is relatively small. The second region 302 has a high doping concentration, high inverted particle number density, and high gain coefficient. Although the incident laser intensity is low, the amplification factor is relatively large. After amplification by the gain crystal 300, the originally high-intensity spectral components are not over-amplified, while the originally low-intensity spectral components are effectively enhanced. The intensity ratio of each wavelength component is maintained, and the output spectral width is not significantly reduced compared to the input spectral width.

[0079] Taking a Yb:YAG crystal as an example, its gain peak wavelength is around 1030 nm. After dispersion by the dispersant 200, the laser component near 1030 nm is incident on the first region 301 with higher intensity; the laser component farther from 1030 nm is incident on the second region 302 with lower intensity. The doping concentration in the first region 301 is lower than that in the second region 302. The amplification factor of the laser component near 1030 nm is relatively small, while the amplification factor of the laser component farther from 1030 nm is relatively large. After amplification, the output spectrum still maintains the overall Gaussian profile, but the spectral width is increased compared to the amplified output spectral width of a traditional uniformly doped gain crystal 300, and the narrowing phenomenon is well suppressed.

[0080] Furthermore, this narrowing suppression effect is more pronounced when the pump light intensity in the first region 301 is lower than that in the second region 302. The first region 301 has a low doping concentration and low pump intensity, resulting in lower gain; the second region 302 has a high doping concentration and high pump intensity, resulting in higher gain. Through dual control of doping concentration and pump intensity, the amplification factor of different wavelength components can be more effectively balanced, thus better preserving the spectral width. Even by controlling the spatial distribution of doping concentration alone, narrowing can be suppressed to a considerable extent.

[0081] It should be noted that the laser intensity incident on the first region 301 is higher than that incident on the second region 302, but this does not mean that the laser intensity in the first region 301 must be higher than that in the second region 302 at every point, nor does it require that the intensity be uniform throughout the first and second regions 301. The laser intensity can vary continuously along the first direction a, as long as the overall laser intensity in the first region 301 is higher than that in the second region 302. Furthermore, for special intensity distributions such as saddle-shaped spectra, there may be concave areas with lower intensity in the middle, but there may still be areas with higher intensity on both sides. The setting of this embodiment can flexibly adapt to different spectral shapes. As long as the overall laser intensity incident on the first region 301 is higher than that in the second region 302, the corresponding narrowing suppression effect can be obtained.

[0082] Please see Figure 2 In some embodiments of this application, the laser light dispersed by the dispersing element 200 has a laser intermediate region 501 and laser edge regions 502 located on both sides of the laser intermediate region 501 along the first direction a. The intensity of the laser light in the laser intermediate region 501 is higher than that in the laser edge regions 502. Along the first direction a, the first region 301 is located in the middle of the gain crystal 300, and the second region 302 is located on both sides of the first region 301 along the first direction a. The laser intermediate region 501 is incident on the first region 301, and the laser edge regions 502 are incident on the second region 302.

[0083] After being dispersed by the dispersive element 200, the laser beam, once spread along the first direction a, exhibits not only wavelength separation but also spatial intensity distribution. In this embodiment, the laser beam dispersed by the dispersive element 200 has a central region 501 and edge regions 502 located on both sides of the central region 501 along the first direction a. The laser intensity of the central region 501 is higher than that of the edge regions 502. In other words, the intensity of the dispersed laser spot is not uniform along the first direction a; rather, the central portion is stronger, while the two sides are weaker.

[0084] For common Gaussian spectral lasers, the spectral intensity is high near the gain peak wavelength and low far from it. After dispersion by the dispersive element 200, the wavelength components near the gain peak wavelength are concentrated in the central region of the laser spot, while those far from the gain peak wavelength are distributed in the edge region. Therefore, the central region 501 of the laser not only has a wavelength closer to the gain peak wavelength but also a relatively high intensity; the edge region 502 of the laser not only has a wavelength far from the gain peak wavelength but also a relatively low intensity. This overlap of wavelength and intensity distributions gives the central region of the laser spot the characteristics of being close to the gain peak wavelength and having high intensity.

[0085] Along the first direction a, a first region 301 of the gain crystal 300 is located in the middle of the gain crystal 300, and a second region 302 is located on both sides of the first region 301 along the first direction a. The doping concentration of active ions in the first region 301 is lower than that in the second region 302, that is, the gain crystal 300 forms a spatial distribution with low doping in the middle and high doping on both sides. The laser in the middle region 501 is incident on the first region 301, and the laser in the edge region 502 is incident on the second region 302. Thus, the laser component with higher intensity and wavelength close to the gain peak wavelength enters the first region 301 with lower doping concentration, and the laser component with lower intensity and wavelength far from the gain peak wavelength enters the second region 302 with higher doping concentration.

[0086] Gain crystal 300 has varying gain capabilities for different wavelength components, while laser light itself exhibits intensity differences, with a strong central component and weaker peripheral components. If a uniformly doped gain crystal 300 is used, the laser components near the gain peak wavelength have inherently high intensity and intrinsic gain, resulting in a greater increase in intensity after amplification; conversely, laser components farther from the gain peak wavelength have inherently low intensity and intrinsic gain, leading to a smaller increase in intensity after amplification. The combined effect is that high-intensity components are amplified more, while low-intensity components are amplified less, further widening the intensity differences between different wavelength components in the spectrum and making spectral narrowing more pronounced.

[0087] This embodiment compensates for the aforementioned effects by incidenting high-intensity components into a lightly doped first region 301 and low-intensity components into a heavily doped second region 302. The first region 301 has a low doping concentration, low inversion particle number density, and low gain coefficient; although the incident laser intensity is high, the amplification factor is relatively small. The second region 302 has a high doping concentration, high inversion particle number density, and high gain coefficient; although the incident laser intensity is low, the amplification factor is relatively large. After amplification by the gain crystal 300, the originally high-intensity spectral components are not over-amplified, while the originally low-intensity spectral components are relatively enhanced. The intensity ratio between different wavelength components is maintained, and the spectral width does not decrease significantly due to amplification.

[0088] In this way, components with higher intensity are placed in regions with lower gain, thus suppressing amplification; components with lower intensity are placed in regions with higher gain, thus enhancing amplification. Through this spatial matching, although the amplified spectrum still maintains the overall Gaussian profile, the spectral width is increased compared to the amplified spectrum of a conventional uniformly doped gain crystal 300, and the narrowing phenomenon is well suppressed.

[0089] Furthermore, if the intensity of the pump light is also lower in the first region 301 than in the second region 302, then the first region 301 will have a lower gain due to the combined effect of low doping and low pumping, while the second region 302 will have a higher gain due to the combined effect of high doping and high pumping, resulting in a more pronounced effect of offsetting the weaker areas. However, even by simply controlling the spatial distribution of doping concentration, the narrowing phenomenon can be suppressed to a considerable extent.

[0090] Please see Figure 9 In some embodiments of this application, along the first direction a, the first region 301 includes a first sub-region 3011, a second sub-region 3012, and a third sub-region 3013 arranged sequentially, with the second sub-region 3012 located between the first sub-region 3011 and the third sub-region 3013; the laser intermediate region 501 is incident on the first sub-region 3011, the second sub-region 3012, and the third sub-region 3013; the wavelength of the laser incident on the second sub-region 3012 is closer to the gain peak wavelength of the gain crystal 300 than the wavelength of the laser incident on the first sub-region 3011 and the third sub-region 3013, and the intensity of the laser incident on the second sub-region 3012 is lower than the intensity of the laser incident on the first sub-region 3011 and the third sub-region 3013.

[0091] In this embodiment, along the first direction a, the first region 301 of the gain crystal 300 includes a first sub-region 3011, a second sub-region 3012, and a third sub-region 3013 arranged sequentially, with the second sub-region 3012 located between the first sub-region 3011 and the third sub-region 3013. The first sub-region 3011, the second sub-region 3012, and the third sub-region 3013 are regions obtained by further spatial division of the first region 301. They are arranged sequentially along the first direction a, with the second sub-region 3012 located in the middle, and the first sub-region 3011 and the third sub-region 3013 located on either side of the second sub-region 3012. All three sub-regions belong to the first region 301, therefore their active ion doping concentrations are all lower than those of the second region 302.

[0092] The laser light, after being dispersed by the dispersant 200, has a central region 501 and an edge region 502 along the first direction a. The central region 501 is incident on the first region 301. Based on this, the central region 501 is incident on the first sub-region 3011, the second sub-region 3012, and the third sub-region 3013. In other words, the spatial range of the central region 501 covers the first sub-region 3011, the second sub-region 3012, and the third sub-region 3013 of the gain crystal 300, and these three sub-regions respectively receive laser components from different spatial locations within the central region 501.

[0093] Because the dispersive element 200 arranges different wavelength components sequentially along the first direction a, and the wavelength changes continuously along the first direction a, different spatial positions within the laser intermediate region 501 correspond to different wavelengths. The second sub-region 3012 is located between the first sub-region 3011 and the third sub-region 3013, corresponding to a spatial position in the middle of the laser intermediate region 501. Therefore, the laser wavelength incident on the second sub-region 3012 is closest to the gain peak wavelength, while the laser wavelengths incident on the first sub-region 3011 and the third sub-region 3013 are relatively far from the gain peak wavelength. Simultaneously, the intensity of the laser incident on the second sub-region 3012 is lower than the intensity of the laser incident on the first sub-region 3011 and the third sub-region 3013. In other words, the intensity distribution within the laser intermediate region 501 is not uniform; the intensity in the middle is lower than the intensity on both sides, forming a central intensity depression. The wavelength corresponding to this intensity depression is close to the gain peak wavelength, while the wavelengths corresponding to the higher intensity portions on both sides are relatively far from the gain peak wavelength.

[0094] This spatial distribution can be understood as follows: while the overall intensity of the laser's central region 501 is higher than that of the laser's edge region 502, the intensity of the central part of the laser's central region 501 is deliberately reduced, forming a saddle-shaped spectral intensity distribution with a low intensity in the middle and high intensity on both sides. The concave part of the saddle shape corresponds precisely to the vicinity of the gain peak wavelength, while the convex parts on both sides correspond to wavelength components that deviate from the gain peak wavelength.

[0095] Laser components near the gain peak wavelength have high intrinsic gain, and can achieve strong amplification even with low input intensity. Conversely, laser components deviating from the gain peak wavelength have low intrinsic gain, requiring higher input intensity to achieve an output intensity comparable to that near the gain peak wavelength after amplification. By pre-suppressing the intensity near the gain peak wavelength at input and retaining the higher intensity at wavelengths deviating from the gain peak wavelength, the intensity distribution can be naturally compensated for during amplification by utilizing the difference in intrinsic gain. At the gain peak wavelength, although the input intensity is low, the gain is high; at wavelengths deviating from the gain peak wavelength, although the input intensity is high, the gain is low. After amplification by the gain crystal 300, the intensity ratio between different wavelength components tends to be balanced, and the spectral width can be well maintained.

[0096] By suppressing the intensity near the gain peak wavelength, an amplification margin is reserved at the gain peak wavelength, preventing it from being over-enhanced after amplification and thus mitigating the gain narrowing effect. This setting, combined with the aforementioned scheme of spatial modulation through doping concentration and pump intensity, can more comprehensively suppress spectral narrowing.

[0097] Taking a Yb:YAG crystal as an example, its peak gain wavelength is around 1030 nm. After dispersion by the dispersant 200, the laser component near 1030 nm corresponds to the center of the laser intermediate region 501 and is incident on the second sub-region 3012; the laser components farther from 1030 nm correspond to the two sides of the laser intermediate region 501 and are incident on the first sub-region 3011 and the third sub-region 3013, respectively. The laser intensity of the second sub-region 3012 is lower than that of the first sub-region 3011 and the third sub-region 3013, forming an intensity depression near 1030 nm. Due to the high intrinsic gain near 1030 nm, this depression will not be significantly lower than the two sides after amplification; while the wavelength components on both sides that are far from 1030 nm have higher input intensity, their intrinsic gain is low, and they will not significantly exceed the components near 1030 nm after amplification. Therefore, the intensity ratio of each wavelength component in the amplified spectrum is maintained, and the spectral width is improved compared to the situation after amplification of a uniform spectrum.

[0098] It should be noted that the intensity recess in the second sub-region 3012 is not required to be strictly symmetrical, nor is it required that the intensities of the first sub-region 3011 and the third sub-region 3013 be exactly the same. As long as the overall laser intensity incident on the second sub-region 3012 is lower than that incident on the first sub-region 3011 and the third sub-region 3013, and the laser wavelength incident on the second sub-region 3012 is closer to the gain peak wavelength, the aforementioned compensation effect can be achieved to a certain extent. Furthermore, the saddle-shaped spectral distribution can be achieved by setting a laser shaping element 600 in the laser optical path before the dispersive element 200, for example, by using a filter to shape the spectrum, reducing the intensity near the gain peak wavelength, forming an intensity distribution that is low in the center and high on both sides. This embodiment does not specifically limit this.

[0099] Please see Figure 9 In some embodiments of this application, the pump light source 400 includes a first pump component 410 for outputting a first pump light 411 and a second pump component 420 for outputting a second pump light 421. The first pump light 411 is incident on one side of the gain crystal 300 along the first direction, and the second pump light 421 is incident on the other side of the gain crystal 300 along the first direction, and the first pump light 411 and the second pump light 421 overlap in the second sub-region 3012.

[0100] In this embodiment, the pump light source 400 includes a first pump component 410 and a second pump component 420. The first pump component 410 outputs a first pump light 411, and the second pump component 420 outputs a second pump light 421. The first pump light 411 and the second pump light 421 are incident on the gain crystal 300 from both sides along the first direction a, and the first pump light 411 and the second pump light 421 overlap in the second sub-region 3012. That is, the two pump lights overlap within the spatial range of the second sub-region 3012, and the second sub-region 3012 simultaneously receives pump light from both sides.

[0101] The second sub-region 3012 corresponds to the concave part of the saddle-shaped spectrum. The wavelength of the laser incident on the second sub-region 3012 is closer to the gain peak wavelength of the gain crystal 300, and the intensity of the laser incident on the second sub-region 3012 is lower than that of the laser incident on the first sub-region 3011 and the third sub-region 3013. If the pump intensity of the second sub-region 3012 is too low, the number of inverted particles is insufficient, and the laser incident on the second sub-region 3012 may not be effectively amplified, and a concave part may appear at the wavelength position corresponding to the second sub-region 3012 in the amplified output spectrum. If the pump intensity of the second sub-region 3012 is too high, the laser incident on the second sub-region 3012 will be over-amplified, weakening the pre-compensation effect of the saddle-shaped spectrum.

[0102] The first pump beam 411 and the second pump beam 421 overlap in the second sub-region 3012, utilizing the weak edge regions of both beams to provide pump energy to the second sub-region 3012. With this configuration, the pump intensity received by the second sub-region 3012 is higher than that irradiated only by the weak edge region of a single pump beam, thus enhancing the pumping of the second sub-region 3012 to a certain extent and preventing a significant dip in the amplified output spectrum at the wavelength corresponding to the second sub-region 3012 due to insufficient pumping. Simultaneously, the overlapping portion of the first pump beam 411 and the second pump beam 421 in the second sub-region 3012 mainly originates from the weak edge regions of the two beams. The overall pump intensity received by the second sub-region 3012 remains lower than the intensity of the strong central region of the pump beam received by the second region 302. Therefore, the gain of the second sub-region 3012 will not be excessively increased due to the overlap, and the pre-compensation effect of the saddle-shaped spectrum is maintained.

[0103] Furthermore, the overlap of the two pump beams in the second sub-region 3012 helps to avoid abrupt drops in pump intensity between adjacent pump regions. The first pump beam 411 and the second pump beam 421 are incident from opposite sides of the gain crystal 300 along the first direction a. If the two pump beams do not overlap spatially, a region with low pump intensity may form at the boundary between the first pump beam 411 and the second pump beam 421, resulting in discontinuous amplification of the corresponding laser components and breakage or unevenness in the amplified output spectrum. By having the two pump beams overlap in the second sub-region 3012, a smoother spatial transition in pump intensity is achieved, which helps to ensure the continuity of pumping in each region of the gain crystal 300 along the first direction a.

[0104] Please see Figure 9 and Figure 10 In some embodiments of this application, the laser amplification device further includes a first pump light shaping component 430 and a second pump light shaping component 440. The first pump light shaping component 430 is disposed in the optical path between the first pump assembly 410 and the gain crystal 300, and the second pump light shaping component 440 is disposed in the optical path between the second pump assembly 420 and the gain crystal 300. The first pump light shaping component 430 is used to shape the first pump light 411 into a first stripe-shaped spot, and the second pump light shaping component 440 is used to shape the second pump light 421 into a second stripe-shaped spot. Both the first and second stripe-shaped spots extend along a first direction a. Both the first and second stripe-shaped spots have a pump light middle region 401 and pump light edge regions 402 located on both sides of the pump light middle region 401. The intensity of the pump light middle region 401 is higher than the intensity of the pump light edge regions 402. The pump light of the first stripe-shaped spot... The light intermediate region 401 is incident on a second region 302 on one side of the first region 301; the pump light edge region 402 of the first stripe light spot is incident on the first sub-region 3011 and at least part of the second sub-region 3012; the pump light intermediate region 401 of the second stripe light spot is incident on the other side of the first region 301; the pump light edge region 402 of the second stripe light spot is incident on the third sub-region 3013 and at least part of the second sub-region 3012; and the first stripe light spot and the second stripe light spot overlap in the second sub-region 3012; the first pump light shaping member 430 is configured to adjust the width of the first stripe light spot along the first direction a, and / or the second pump light shaping member 440 is configured to adjust the width of the second stripe light spot along the first direction a, so as to adjust the width of the overlapping region formed by the overlap of the first stripe light spot and the second stripe light spot in the second sub-region 3012 along the first direction a.

[0105] In this embodiment, the laser amplification device may further include a first pump light shaping component 430 and a second pump light shaping component 440. The first pump light shaping component 430 is disposed in the optical path between the first pump assembly 410 and the gain crystal 300, and is used to receive the first pump light 411 output by the first pump assembly 410 and spatially shape the first pump light 411. The second pump light shaping component 440 is disposed in the optical path between the second pump assembly 420 and the gain crystal 300, and is used to receive the second pump light 421 output by the second pump assembly 420 and spatially shape the second pump light 421. The first pump light shaping component 430 shapes the first pump light 411 into a first stripe-shaped spot, and the second pump light shaping component 440 shapes the second pump light 421 into a second stripe-shaped spot. Both the first and second stripe-shaped spots extend along a first direction a.

[0106] The pump light shaping component can be a cylindrical lens, a lens group, or other optical elements capable of altering the spatial intensity distribution of the pump light. The shaped first and second stripe-shaped light spots have a certain length along the first direction a and a certain width perpendicular to the first direction a. Both the first and second stripe-shaped light spots have a pump light central region 401 and pump light edge regions 402 located on either side of the central region 401. The intensity of the central region 401 is higher than that of the edge regions 402. In other words, the intensity distribution of the first and second stripe-shaped light spots along the first direction a exhibits a strong central distribution and a weaker distribution on both sides. Specifically, the first and second stripe-shaped light spots can be elliptical spots or rectangular flat-topped stripe-shaped spots, etc., with the length direction of the spots extending along the first direction a and the width direction perpendicular to the first direction a.

[0107] The pump light from the first stripe-shaped spot has its central region 401 incident on a second region 302 located on one side of the first region 301, and its edge region 402 incident on a first sub-region 3011 and at least a portion of the second sub-region 3012. The pump light from the second stripe-shaped spot has its central region 401 incident on the other side of the first region 301, and its edge region 402 incident on a third sub-region 3013 and at least a portion of the second sub-region 3012. Thus, the first and second stripe-shaped spots overlap in the second sub-region 3012. In other words, the coverage areas of the two stripe-shaped spots overlap in the second sub-region 3012, and the second sub-region 3012 simultaneously receives the weak edge regions of the pump light from both the first and second stripe-shaped spots.

[0108] The coverage areas of the first and second stripe-shaped light spots correspond to the spatial positions of the first region 301, the second region 302, and the first sub-region 3011, the second sub-region 3012, and the third sub-region 3013 in the gain crystal 300. The strong pump light regions in the middle of the two stripe-shaped light spots respectively illuminate the second regions 302 on both sides, providing a high pump intensity for the laser components far from the gain peak wavelength; the weak pump light regions at the edges of the two stripe-shaped light spots respectively illuminate the first sub-region 3011 and the third sub-region 3013, providing a lower pump intensity for the laser components close to the gain peak wavelength but relatively far from the center; the weak pump light regions at the edges of the two stripe-shaped light spots also overlap in the second sub-region 3012, providing moderate pump reinforcement for the laser components near the gain peak wavelength.

[0109] The first pump light shaping element 430 is configured to adjust the width of the first stripe light spot along the first direction a, and the second pump light shaping element 440 is configured to adjust the width of the second stripe light spot along the first direction a. In practical use, only the first pump light shaping element 430, only the second pump light shaping element 440, or both can be adjusted simultaneously. By adjusting the width of the stripe light spot along the first direction a, the coverage area of ​​the stripe light spot along the first direction a can be changed, thereby adjusting the width of the overlapping area formed by the first and second stripe light spots in the second sub-region 3012 along the first direction a. The change in the width of the overlapping area along the first direction a affects the spatial range and pump intensity of the pump light received by the second sub-region 3012. When the width of the overlapping region increases, the second sub-region 3012 receives more pump light, and the pump intensity increases; when the width of the overlapping region decreases, the second sub-region 3012 receives less pump light, and the pump intensity decreases.

[0110] By adjusting the first pump light shaping element 430, the second pump light shaping element 440, or both simultaneously, the pump reinforcement level of the second sub-region 3012 can be flexibly controlled, ensuring that the pump intensity received by the second sub-region 3012 is neither too low nor too high. This allows for appropriate amplification of the laser components near the gain peak wavelength, preventing a dip in the output spectrum due to insufficient pumping or excessive amplification due to excessive pumping. This maintains the saddle-shaped spectral pre-compensation effect, helps suppress gain narrowing effects, and achieves broadband laser output.

[0111] Please see Figure 9 and Figure 10In some embodiments of this application, the laser amplification device further includes a laser shaping component 600, which is disposed in the optical path between the laser source 100 and the dispersive component 200, and is used to perform spectral shaping on the laser emitted by the laser source 100 so that the intensity of the laser incident on the second sub-region 3012 is lower than the intensity of the laser incident on the first sub-region 3011 and the third sub-region 3013; the laser shaping component 600 is configured to adjust the laser intensity difference between the second sub-region 3012 and the first sub-region 3011 and the third sub-region 3013.

[0112] The laser amplification device may also include a laser shaping component 600. The laser shaping component 600 is disposed in the optical path between the laser source 100 and the dispersive element 200, meaning that the laser emitted from the laser source 100 first passes through the laser shaping component 600 before entering the dispersive element 200. The laser shaping component 600 is used to perform spectral shaping on the laser emitted from the laser source 100, causing a change in the spectral intensity distribution of the laser before it enters the dispersive element 200.

[0113] The laser shaping component 600 can employ optical elements or assemblies capable of altering the spectral intensity distribution. For example, the laser shaping component 600 may include a filter that attenuates the intensity of specific wavelength components through filtering, thereby changing the intensity ratio between different wavelength components. The laser shaping component 600 may also employ spatial light modulators, grating pairs, prism pairs, or other devices capable of spectral shaping; this embodiment does not impose specific limitations on this.

[0114] After the laser shaping component 600 performs spectral shaping on the laser, the intensity of the laser incident on the second sub-region 3012 after dispersion by the dispersive component 200 is lower than the intensity of the laser incident on the first sub-region 3011 and the third sub-region 3013. In other words, the laser shaping component 600 pre-adjusts the spectral intensity distribution before the laser enters the dispersive component 200, resulting in lower intensity of wavelength components in the second sub-region 3012 and higher intensity of wavelength components in the first and third sub-regions 3011 and 3013 after dispersion. Since the second sub-region 3012 corresponds to wavelength components near the gain peak wavelength, and the first and third sub-regions 3011 and 3013 correspond to wavelength components deviating from the gain peak wavelength, the function of the laser shaping component 600 is to suppress the intensity near the gain peak wavelength while retaining or increasing the intensity at wavelengths deviating from the gain peak wavelength, forming a saddle-shaped spectral intensity distribution that is low in the middle and high on both sides.

[0115] The reason for this configuration is that laser components near the gain peak wavelength have higher intrinsic gain in the gain crystal 300, and can achieve strong amplification even with lower input intensity. Conversely, laser components deviating from the gain peak wavelength have lower intrinsic gain, requiring higher input intensity to achieve an output intensity comparable to that near the gain peak wavelength after amplification. By pre-suppressing the intensity near the gain peak wavelength at input using the laser shaping component 600, the intensity distribution can be compensated for during amplification by utilizing the difference in intrinsic gain. This results in a more balanced intensity ratio among the wavelength components after amplification, which helps suppress the gain narrowing effect and maintain spectral width.

[0116] The laser shaping component 600 is also configured to adjust the laser intensity difference between the second sub-region 3012 and the first sub-region 3011 and the third sub-region 3013. In other words, the degree of spectral shaping by the laser shaping component 600 is adjustable, and the intensity difference between the second sub-region 3012 and the two adjacent sub-regions can be changed according to actual needs. When the gain narrowing of the gain crystal 300 is strong, this intensity difference can be increased, i.e., the intensity corresponding to the second sub-region 3012 can be further reduced to compensate for the stronger intrinsic gain difference; when the gain narrowing is weak, this intensity difference can be reduced to avoid excessive reduction leading to insufficient intensity of the wavelength component corresponding to the second sub-region 3012 after amplification.

[0117] The laser intensity difference can be adjusted by changing the parameters of the laser shaping component 600. For example, when the laser shaping component 600 includes a filter, the filter depth or filter bandwidth can be adjusted to change the degree of intensity attenuation near the gain peak wavelength. Adjusting the laser intensity difference allows the laser amplification device to adapt to different requirements for spectral pre-compensation under different gain crystals 300 and different spectral distributions, improving the flexibility and applicability of the device.

[0118] By setting the laser shaping component 600 and adjusting the laser intensity difference between the second sub-region 3012 and the two side sub-regions, the depth of the saddle-shaped spectrum can be controlled more precisely, so that the input intensity near the gain peak wavelength matches the intrinsic gain characteristics of the gain crystal 300. This achieves better gain balance during amplification, which is beneficial for obtaining a wide-spectrum laser output and provides a foundation for obtaining a femtosecond laser with a narrow pulse width in the future.

[0119] The foregoing embodiments have illustrated the basic structure and working principle of the laser amplification device provided in this embodiment. The specific optical path structure and optical components of this laser amplification device will be illustrated with examples below. Please refer to... Figure 9 and Figure 11In this embodiment, the laser amplification device, along the laser propagation direction, sequentially includes a seed source 1, a stretcher 2, an fiber amplifier 3, a filter 4, a diffraction grating 5, a first climbing mirror 6, and a first corner mirror 7. The laser light reflected by the first corner mirror 7 enters the solid-state amplification module. The solid-state amplification module includes a focusing lens 8, a half-wave plate 9, a polarizing beam splitter 10, a first dichroic mirror 11, a bonding crystal 12, a second dichroic mirror 13, a quarter-wave plate 14, and a concave mirror 15. Pump light is provided by a pump module, which includes a first pump source 16, a first pump collimating lens 17, a first pump shaping cylindrical lens group, a second pump source 20, a second pump collimating lens 21, and a second pump shaping cylindrical lens group. The laser light amplified by the solid-state amplification module enters the compression module. The compression module includes a collimating lens 24, a compression grating 25, a second climbing mirror 26, and a second corner mirror 27.

[0120] Seed source 1 is used to generate a stable sequence of femtosecond laser pulses, serving as the initial light source for the entire laser amplification device. The laser wavelength output by seed source 1 is around 1030 nm. The output of seed source 1 is connected to the input optical path of stretcher 2. Stretcher 2 is used to temporally stretch the femtosecond laser pulse sequence output by seed source 1 to reduce the peak power and nonlinear effects in the subsequent amplification process. Stretcher 2 can be an adjustable chirped fiber Bragg grating dispersion-managed reflector. The output of stretcher 2 is connected to the input optical path of fiber amplifier 3. Fiber amplifier 3 is used to pre-amplify the stretched laser pulses to achieve power enhancement. The fiber used in fiber amplifier 3 can be large-mode-area double-clad fiber, tapered fiber, or photonic crystal fiber. The output of fiber amplifier 3 is connected to the input optical path of filter 4. Seed source 1, stretcher 2, and fiber amplifier 3 together form laser source 100.

[0121] Filter 4 is used to shape the laser pulse spectrum output from fiber amplifier 3, obtaining a saddle-shaped spectrum with a low center and high sides, providing a basis for gain narrowing compensation in the subsequent amplification process. Filter 4 can be a birefringent filter or a spectral comb shaping filter. The output of filter 4 is connected to the input optical path of diffraction grating 5.

[0122] The diffraction grating 5 is a dispersive element 200 used to spatially disperse the filtered laser light, separating different wavelength components of the laser light spatially along the first direction a to form a spatially distributed spectrum. The diffraction grating 5 can be a transmission type. The laser light dispersed by the diffraction grating 5 is incident on the first ascending reflector 6. The first ascending reflector 6 is used to guide the laser light, after being dispersed by the diffraction grating 5, back along the original optical path to the diffraction grating 5, allowing the laser light to pass through the diffraction grating 5 again, thus enhancing the dispersion effect. The laser light, after passing through the diffraction grating 5 again, is incident on the first corner mirror 7. The first corner mirror 7 is used to reflect the laser light, after passing through the diffraction grating 5 again, out of the main optical path and into the solid-state amplification module. The focusing lens 8 is disposed on the outgoing optical path of the first corner mirror 7, used to spatially converge the dispersed laser light, so that the focal point of the laser light is located near the incident surface of the bonded crystal 12. A half-wave plate 9 is disposed between the focusing lens 8 and the polarizing beam splitter 10. By rotating the half-wave plate 9, the polarization state of the laser can be adjusted, allowing the entire laser beam to pass through the polarizing beam splitter 10. The polarizing beam splitter 10 is used to separate the incident laser beam from the laser beam that returns after being amplified twice by the bonding crystal 12.

[0123] The first dichroic mirror 11 is disposed between the polarizing beam splitter 10 and the bonding crystal 12 to reflect laser light into the bonding crystal 12. The first dichroic mirror 11 is highly reflective of laser light with a wavelength of 1030 nm and highly transparent to pump light with a wavelength of 940 nm.

[0124] The bonded crystal 12, as a gain crystal 300, is used to amplify the incident laser. The bonded crystal 12 is a crystal doped with active ions, such as a Yb:YAG crystal, i.e., a yttrium aluminum garnet doped crystal. The bonded crystal 12 is formed by bonding multiple crystal segments along a first direction a, with adjacent crystal segments having different active ion doping concentrations. In this embodiment, the bonded crystal 12 has a first region 301 along the first direction a and second regions 302 located on both sides of the first region 301 along the first direction a. The active ion doping concentration of the first region 301 is lower than that of the second region 302. The doping concentration distribution of the bonded crystal 12 along the first direction a can be, for example, a region with a doping concentration of 1% in the middle, and regions with doping concentrations of 2% and 2.5% on both sides, forming a stepped doping distribution with a low concentration in the middle and high concentrations on both sides. When the laser light dispersed by the diffraction grating 5 is incident on the bonding crystal 12, the laser component with a wavelength closer to the gain peak wavelength is incident on the first region 301, and the laser component with a wavelength farther from the gain peak wavelength is incident on the second region 302.

[0125] The second dichroic mirror 13 is disposed on the other side of the bonding crystal 12 and is used to transmit pump light and reflect laser light. The second dichroic mirror 13 is also highly reflective of 1030nm wavelength laser light and highly transparent of 940nm wavelength pump light.

[0126] A quarter-wave plate 14 is positioned between the bonding crystal 12 and the concave mirror 15. After being amplified by the bonding crystal 12, the laser light is reflected by the second dichroic mirror 13, then incident on the concave mirror 15 via the quarter-wave plate 14. Reflected by the concave mirror 15, the laser light again passes through the quarter-wave plate 14 and the bonding crystal 12, achieving double-pass amplification. The amplified laser light is then separated and output by the polarizing beam splitter 10, and enters the subsequent compression module.

[0127] The first pump light source 16 outputs a first pump light 411 with a wavelength around 940 nm. After being collimated by the first pump collimating lens 17, the first pump light 411 is shaped by the first pump shaping cylindrical lens group to form a first stripe-shaped light spot extending along the first direction a, and then focused into the bonding crystal 12. The first pump shaping cylindrical lens group may include multiple cylindrical lenses for shaping the fast and slow axes of the first pump light 411, respectively. For example, this embodiment uses two cylindrical lenses: a first pump pre-shaping cylindrical lens 18 and a first pump post-shaping cylindrical lens 19. The first pump light 411 is transmitted from one side of the bonding crystal 12 through the first dichroic mirror 11 and then incident on the bonding crystal 12.

[0128] The second pump light source 20 outputs a second pump light 421 with a wavelength around 940 nm. After being collimated by the second pump collimating lens 21, the second pump light 421 is shaped by the second pump shaping cylindrical lens group to form a second stripe-shaped light spot extending along the first direction a, and focused into the bonding crystal 12. The second pump shaping cylindrical lens group also includes two cylindrical lenses: a second pre-pump shaping cylindrical lens 22 and a second post-pump shaping cylindrical lens 23. The second pump light 421 is transmitted from the other side of the bonding crystal 12 through the second dichroic mirror 13 and then incident on the bonding crystal 12.

[0129] Both the first and second stripe-shaped light spots have a pump light intermediate region 401 and pump light edge regions 402 located on both sides of the pump light intermediate region 401. The intensity of the pump light intermediate region 401 is higher than that of the pump light edge regions 402. The pump light intermediate region 401 of the first stripe-shaped light spot is incident on a second region 302 on one side of the first region 301, and the pump light edge regions 402 of the first stripe-shaped light spot are incident on a first sub-region 3011 and at least a portion of the second sub-region 3012. The pump light intermediate region 401 of the second stripe-shaped light spot is incident on a second region 302 on the other side of the first region 301, and the pump light edge regions 402 of the second stripe-shaped light spot are incident on a third sub-region 3013 and at least a portion of the second sub-region 3012. The first and second stripe-shaped light spots overlap in the second sub-region 3012, such that the region with the highest pump intensity is located in the convex portion of the saddle-shaped spectrum, and the overlapping region is located in the concave portion of the saddle-shaped spectrum.

[0130] By moving the positions of the first pump light source 16, the second pump light source 20, and the corresponding pump collimating lens and pump shaping cylindrical lens group, the position of the pump overlap region and the pump focal point can be adjusted. By replacing the cylindrical lens in the pump shaping cylindrical lens group, the focal point size of the pump focused into the bonding crystal 12 can be adjusted.

[0131] The laser beam, after being amplified twice by the bonding crystal 12, enters the compression module. The compression module includes a collimating lens 24, a compression grating 25, a second climbing mirror 26, and a second corner mirror 27. The amplified laser beam is collimated by the collimating lens 24 and then incident on the compression grating 25. After diffraction by the compression grating 25, the beam is output to the second climbing mirror 26, then climbs back to the compression grating 25. Adjusting the position of the compression grating 25 compresses the laser pulse to its narrowest point, and finally, the laser beam is output from the second corner mirror 27, completing the compression process.

[0132] Figure 12 , Figure 13 , Figure 14 The output laser spectra obtained after amplifying the laser using three different techniques are shown. The horizontal axis of each of the three spectra is wavelength (nm), representing the wavelength corresponding to each spectral component of the output laser. The vertical axis is intensity (au, any unit), representing the relative spectral signal intensity at each wavelength. The spectral vertical axis has been normalized to uniformly set the intensity of the spectral peaks to 1, facilitating a direct comparison of the changes in spectral line profiles and full width at half maximum (FWHM) under different amplification conditions.

[0133] Specifically Figure 12 The laser spectrum is amplified using a related technique. The spectrum is obtained by directly amplifying the unshaped laser and the full width at half maximum (FWHM) of the spectrum is 2.4 nm. Figure 13 This is a magnified laser spectrum obtained using another related technique, specifically by shaping the laser into a saddle shape before amplification. The full width at half maximum (FWHM) of this spectrum is 4.1 nm. (Comparison) Figure 12 It can be seen that the full width at half maximum (FWHM) of the spectrum obtained by this amplification scheme is larger than that of the direct amplification without shaping, and the narrowing of gain is alleviated to a certain extent. Figure 14 The image shows a laser spectrum amplified using the laser amplification device described in this embodiment, with a full width at half maximum (FWHM) of 6.0 nm. (Comparison) Figure 12 , Figure 13As can be seen from the spectrum, after amplification using the laser amplification device of this application embodiment, more of the original spectral bandwidth is preserved, and the gain narrowing phenomenon is significantly improved. According to the Fourier transform limit principle, for transform-limited laser pulses, the pulse width is inversely proportional to the spectral bandwidth; that is, the larger the spectral bandwidth, the smaller the theoretical minimum pulse width that can be achieved. Therefore, this application embodiment can retain relatively more spectral bandwidth during the amplification process, providing favorable conditions for subsequently obtaining femtosecond laser output with narrow pulse widths.

[0134] The above are merely preferred embodiments of this application and are not intended to limit this application. The technical solutions of the various embodiments in this application can be arbitrarily combined without conflict, and the resulting technical solutions also fall within the protection scope of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A laser amplification device, characterized in that, The laser amplification device includes: Laser source; the laser source is used to generate laser light; Dispersive element; the dispersive element is used to spatially disperse laser light incident from the laser source, so that different wavelength components of the laser light are spatially separated along a first direction; Gain crystal; the gain crystal is disposed in the optical path of the laser after dispersion by the dispersive element, and is used to amplify the dispersed laser. The gain crystal is doped with activating ions. A pump source; the pump source is used to output pump light and emit it to the gain crystal, providing pump energy for the gain crystal to amplify the laser; Along the first direction, the gain crystal has a first region and a second region, wherein the doping concentration of active ions in the first region is lower than the doping concentration of active ions in the second region. The laser light dispersed by the dispersive element is incident on the first region and the second region, and the wavelength of the laser light incident on the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident on the second region.

2. The laser amplification device as described in claim 1, characterized in that, The laser light dispersed by the dispersive element has a laser center region and laser edge regions located on both sides of the laser center region along the first direction. The wavelength of the laser light in the laser center region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light in the laser edge region. Along the first direction, the first region is located in the middle of the gain crystal, and the second region is located on both sides of the first region along the first direction; The laser's central region is incident on the first region, and the laser's edge region is incident on the second region.

3. The laser amplification device as described in claim 1 or 2, characterized in that, The pump light is incident on the first region and the second region, and the intensity of the pump light in the first region is lower than that in the second region.

4. The laser amplification device as described in claim 1, characterized in that, The intensity of the laser after dispersion by the dispersive element varies along the first direction, and the intensity of the laser incident on the first region is higher than the intensity of the laser incident on the second region.

5. The laser amplification device as described in claim 4, characterized in that, The laser light dispersed by the dispersive element has a central region and edge regions located on both sides of the central region along the first direction. The intensity of the laser light in the central region is higher than that in the edge regions. Along the first direction, the first region is located in the middle of the gain crystal, and the second region is located on both sides of the first region along the first direction; The laser's central region is incident on the first region, and the laser's edge region is incident on the second region.

6. The laser amplification device as described in claim 5, characterized in that, Along the first direction, the first region includes a first sub-region, a second sub-region, and a third sub-region arranged in sequence, with the second sub-region located between the first sub-region and the third sub-region; The laser's central region is incident on the first sub-region, the second sub-region, and the third sub-region; The wavelength of the laser incident on the second sub-region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser incident on the first and third sub-regions, and the intensity of the laser incident on the second sub-region is lower than the intensity of the laser incident on the first and third sub-regions.

7. The laser amplification device as described in claim 6, characterized in that, The pump light source includes a first pump component for outputting a first pump light and a second pump component for outputting a second pump light. The first pump light is incident on one side of the gain crystal along the first direction, and the second pump light is incident on the other side of the gain crystal along the first direction, and the first pump light and the second pump light overlap in the second sub-region.

8. A laser amplification device, characterized in that, The laser amplification device includes: Laser source; the laser source is used to generate laser light; Dispersive element; the dispersive element is used to spatially disperse laser light incident from the laser source, so that different wavelength components of the laser light are spatially separated along a first direction; Gain crystal; the gain crystal is disposed in the optical path of the laser after dispersion by the dispersive element, and is used to amplify the dispersed laser. The gain crystal is doped with activating ions. A pump source; the pump source is used to output pump light and emit it to the gain crystal, providing pump energy for the gain crystal to amplify the laser; Along the first direction, the gain crystal has a first region and a second region. The laser light dispersed by the dispersing element is incident on the first region and the second region. The wavelength of the laser light incident on the first region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light incident on the second region. The pump light is incident on the first region and the second region, and the intensity of the pump light in the first region is lower than that in the second region.

9. The laser amplification device as described in claim 8, characterized in that, The laser light dispersed by the dispersive element has a laser center region and laser edge regions located on both sides of the laser center region along the first direction. The wavelength of the laser light in the laser center region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser light in the laser edge region. Along the first direction, the first region is located in the middle of the gain crystal, and the second region is located on both sides of the first region along the first direction; The laser's central region is incident on the first region, and the laser's edge region is incident on the second region.

10. The laser amplification device as described in claim 8, characterized in that, The intensity of the laser after dispersion by the dispersive element varies along the first direction, and the intensity of the laser incident on the first region is higher than the intensity of the laser incident on the second region.

11. The laser amplification device as described in claim 10, characterized in that, The laser light dispersed by the dispersive element has a central region and edge regions located on both sides of the central region along the first direction. The intensity of the laser light in the central region is higher than that in the edge regions. Along the first direction, the first region includes a first sub-region, a second sub-region, and a third sub-region arranged in sequence, with the second sub-region located between the first sub-region and the third sub-region; The laser's central region is incident on the first sub-region, the second sub-region, and the third sub-region; The wavelength of the laser incident on the second sub-region is closer to the gain peak wavelength of the gain crystal than the wavelength of the laser incident on the first sub-region and the third sub-region, and the intensity of the laser incident on the second sub-region is lower than the intensity of the laser incident on the first sub-region and the third sub-region. The pump light source includes a first pump component and a second pump component. The first pump light output by the first pump component and the second pump light output by the second pump component are respectively incident on the gain crystal from both sides along the first direction, and the first pump light and the second pump light overlap in the second sub-region.

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