Quasi-three-level laser with end-side composite pumping

Abstract

The invention relates to the technical field of solid laser, and discloses a quasi-three-level laser with end-side composite pumping, which comprises a quasi-three-level laser crystal, an end-side pumping assembly, a side pumping module and a laser resonant cavity. The end face pumping assembly is used for injecting end face pumping light to the end face of the crystal. The side pumping module is used for injecting side pumping light to the side face of the crystal, and the laser resonant cavity and the quasi-three-level laser crystal are matched to form a laser oscillation circuit. Through the arrangement, the end face pumping assembly is used for providing high-power-density pumping light, the problem of high excitation threshold of the quasi-three-level laser crystal is solved, and population inversion and laser gain are effectively established; and meanwhile, large-area and high-pumping power input is carried out by virtue of the side pumping module, so that uniform allocation of a pumping heat load, reduction of a temperature gradient and end surface stress in the crystal and inhibition of a thermal lens effect are effectively realized, consideration of high-power density excitation of the crystal, low thermal stress and uniform thermal distribution is realized, and high-efficiency and high-power laser output of the laser is ensured.

Description

Technical Field

[0001] This invention relates to the field of solid-state laser technology, and more particularly to a quasi-three-level laser with end-side composite pumping. Background Technology

[0002] With the rapid development of solid-state laser technology, high-power, high-efficiency, and high-beam-quality solid-state end-side-pumped quasi-three-level lasers are increasingly widely used in key fields such as industrial processing, medical treatment, and national defense equipment, becoming core equipment driving technological upgrades in related industries. Quasi-three-level laser crystals, with their outstanding advantages such as high quantum efficiency, excellent thermodynamic stability, and wide absorption spectrum, have become an ideal choice for achieving high-power laser output and have attracted much attention from the industry.

[0003] However, the energy level structure of quasi-three-level laser crystals has unique characteristics. At room temperature, their laser-induced energy levels naturally exhibit a certain particle number distribution. To achieve population inversion and generate stable laser oscillations, a sufficiently high power density from the pump light is required. Currently, the mainstream pumping schemes in the industry are mainly divided into two categories: end-pumping and side-pumping. However, for quasi-three-level laser crystals, both single pumping structures have inherent defects that are difficult to overcome.

[0004] Traditional end-pumped structures achieve pumping by focusing the pump light onto the end face of the laser crystal. Their core advantage lies in the concentrated pump spot and ease of achieving high power density, meeting the stringent power density requirements of quasi-three-level laser crystals and thus overcoming the high-threshold limitation of the crystal. However, the pump power of this structure is highly concentrated in the end face and near-end face region, leading to a huge temperature gradient within the crystal and causing severe thermal lensing. This not only degrades the laser beam quality but also significantly reduces the stability of the laser output. Simultaneously, the excessively high local thermal load causes the stress on the crystal end face to approach the fracture threshold, severely limiting further increases in pump power and making it difficult to achieve high-power laser output.

[0005] Traditional side-pumped structures pump the laser crystal by irradiating the side surface with pump light. This results in a large pump area, uniform heat distribution, and easier thermal management, enabling higher power pump input. However, the large pump area also means that it is difficult to achieve sufficiently high power density. When used in quasi-three-level laser crystal applications, it is difficult to overcome the reabsorption loss caused by the population distribution of the lower levels, thus making it impossible to establish effective population inversion and laser gain.

[0006] Therefore, existing end-pump or side-pump structures cannot simultaneously resolve the core contradiction between high power density excitation and low thermal stress required for high power output of quasi-three-level laser crystals. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a quasi-three-level laser with end-side composite pumping.

[0008] This invention provides a quasi-trilevel laser with end-side composite pumping, comprising: a quasi-trilevel laser crystal; an end-side pumping assembly for emitting end-side pump light onto the end face of the quasi-trilevel laser crystal; a side-side pumping module for emitting side-side pump light onto the side face of the quasi-trilevel laser crystal; and a laser resonant cavity that cooperates with the quasi-trilevel laser crystal to cause the laser generated by the stimulated quasi-trilevel laser crystal to oscillate and be output within the laser resonant cavity.

[0009] According to the present invention, a quasi-triple-level laser with end-side composite pumping is provided, wherein the end-side pumping assembly includes: a first end-side pumping module disposed at one end of the quasi-triple-level laser crystal; and a second end-side pumping module disposed at the other end of the quasi-triple-level laser crystal.

[0010] The side-pumping module includes: multiple semiconductor laser arrays, each of which is arranged in a ring around the side of the quasi-three-level laser crystal, and the irradiation length of the semiconductor laser arrays is capable of covering the doped region of the quasi-three-level laser crystal.

[0011] According to the present invention, a quasi-triple-level laser with end-side composite pumping is provided, the quasi-triple-level laser with end-side composite pumping further includes: a first temperature control module, the first temperature control module being connected to the end-side pumping component, for adjusting the temperature of the end-side pumping component so that the end-side pump light wavelength of the end-side pumping component deviates from the peak absorption wavelength of the doped region of the quasi-triple-level laser crystal; and a second temperature control module, the second temperature control module including a first cooling channel and a second cooling channel.

[0012] The first cooling channel is connected to the side pump module and is used to adjust the temperature of the side pump module so that the wavelength of the side pump light emitted by the side pump module is aligned with the peak absorption wavelength of the doped region of the quasi-three-level laser crystal.

[0013] The second cooling channel is connected to the quasi-three-level laser crystal and is used to adjust the temperature of the quasi-three-level laser crystal to reduce the particle number occupancy factor of the laser level of the quasi-three-level laser crystal.

[0014] According to the present invention, an end-side-pumped quasi-triple-level laser further includes: a first beam shaping component disposed between one end of the first end-side-pumping module and one end of the quasi-triple-level laser crystal, and used to collimate and focus the end-side pump light of the first end-side-pumping module; and a second beam shaping component disposed between the other end of the second end-side-pumping module and the quasi-triple-level laser crystal, and used to collimate and focus the end-side pump light of the second end-side-pumping module.

[0015] According to the present invention, a quasi-tri-level laser with end-side composite pumping is provided, wherein the laser resonant cavity includes: a first resonant cavity mirror disposed between a first beam shaping component and one end of the quasi-tri-level laser crystal; a second resonant cavity mirror disposed between the second beam shaping component and the other end of the quasi-tri-level laser crystal; and a laser output mirror, wherein the laser output mirror, together with the first and second resonant cavity mirrors, forms a laser resonant cavity, so that the laser generated by the quasi-tri-level laser crystal under stimulation oscillates within the laser resonant cavity and is output from the laser output mirror.

[0016] According to the present invention, a quasi-three-level laser with end-side composite pumping is provided, wherein the first resonant cavity mirror and the second resonant cavity mirror are plane mirrors or plano-concave mirrors.

[0017] The first resonant cavity mirror has an incident angle of 0°, and the second resonant cavity mirror has an incident angle of 45°. The first resonant cavity mirror, the second resonant cavity mirror, and the laser output mirror together constitute an L-shaped laser resonant cavity.

[0018] Both the first and second resonant cavity mirrors are coated with a dual-color film so that the transmittance of the first and second resonant cavity mirrors to the end face pump light is not less than 98%, and the wavelength reflectance of the first and second resonant cavity mirrors to the output laser is not less than 99.5%.

[0019] The laser output mirror has a laser transmittance of 10%-30%.

[0020] According to the present invention, a quasi-triple-level laser with end-side composite pumping is provided, wherein the quasi-triple-level laser crystal is a rod-shaped crystal.

[0021] The quasi-three-level laser crystal is a ytterbium-doped laser crystal, or a thulium-doped laser crystal, or a holmium-doped laser crystal.

[0022] The two-terminal bond of the quasi-three-level laser crystal is an undoped crystal matrix.

[0023] According to the present invention, a quasi-three-level laser with end-side composite pumping is provided, wherein the quasi-three-level laser crystal is a ytterbium-doped laser crystal; and the undoped crystal in the same matrix is ​​a YAG crystal.

[0024] According to the present invention, a quasi-three-level laser with end-side composite pumping is provided, wherein the temperature adjustment range of the first cooling channel is 15℃-28℃; and the temperature adjustment range of the second cooling channel is 5℃-18℃.

[0025] According to the present invention, a quasi-three-level laser with end-side composite pumping is provided, wherein both the first end-side pumping module and the second end-side pumping module are output via fiber coupling.

[0026] The quasi-trilevel laser with end-side and side-side combined pumping provided by this invention includes a quasi-trilevel laser crystal, an end-side pumping assembly, a side-side pumping module, and a laser resonant cavity. The end-side pumping assembly provides end-side pump light, and the side-side pumping module provides side-side pump light. The end-side pumping assembly is positioned corresponding to the end face of the quasi-trilevel laser crystal to inject end-side pump light into the end face, and the side-side pumping module is positioned corresponding to the side face of the quasi-trilevel laser crystal to inject side-side pump light into the side face. The laser resonant cavity and the quasi-trilevel laser crystal cooperate to form a laser oscillation circuit. The quasi-trilevel laser crystal generates laser light under the synergistic excitation of the end-side and side-side pump light, and the laser light oscillates within the laser resonant cavity and is output outwards.

[0027] During operation, the end-pumping module emits high-power-density end-pump light onto the end face of the quasi-three-level laser crystal, while the side-pumping module emits wide-coverage side-pump light onto the sides of the crystal. These two types of pump light are incident on the interior of the quasi-three-level laser crystal from the end face and side face, respectively. The high power density provided by the end-pump light satisfies the requirement of population inversion and clearing the energy levels in the quasi-three-level laser crystal, overcoming the high threshold characteristic of the crystal. Simultaneously, the side-pump light distributes the heat load through a large-area irradiation, avoiding the localized heat accumulation problem caused by pure end-pumping. Under the synergistic effect of the two types of pump light, the quasi-three-level laser crystal is stimulated to generate laser light. The laser light enters the laser resonant cavity, undergoes multiple reflections and oscillations to achieve energy amplification, and finally forms a stable high-power laser light for output.

[0028] With this structural configuration, the end-pump assembly can provide high-power-density end-pump light to the quasi-trilevel laser crystal, precisely meeting the high-power-density excitation requirements for population inversion and ensuring effective establishment of population inversion and laser gain. The side-pump module emits pump light from the side of the quasi-trilevel laser crystal, which can achieve uniform distribution of pump heat load, significantly reduce the temperature gradient inside the crystal, effectively suppress the thermal lensing effect, and significantly reduce the stress on the crystal end face. This achieves a balance between high-power-density excitation and low thermal stress and uniform heat distribution in the quasi-trilevel laser crystal, ensuring that the end-side-pumped quasi-trilevel laser can stably achieve high-power laser output. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a simplified structural diagram of the end-side composite-pumped quasi-three-level laser provided by the present invention.

[0031] Figures 2(a) and 2(b) are simulated temperature field distribution diagrams of the quasi-three-level laser crystal (yz section) when using a conventional end-face pumping structure and the end-face composite pumping structure of the present invention, respectively, under the same pumping power.

[0032] Figures 3(a) and 3(b) are simulation distribution diagrams of the stress field of the quasi-three-level laser crystal (yz section) when using the traditional end-face pumping structure and the end-face composite pumping structure of the present invention, respectively, under the same pumping power. Figures 4(a) and 4(b) are simulated distributions of axial cumulative inversion particle number density of quasi-three-level laser crystals when using a conventional side-pumping structure and an end-side composite pumping structure of the present invention, respectively, under the same pump power.

[0033] Reference numerals: 100, Quasi-three-level laser crystal; 210, First end-face pump module; 220, Second end-face pump module; 300, Side pump module; 410, First beam shaping assembly; 420, Second beam shaping assembly; 510, First resonant cavity mirror; 520, Second resonant cavity mirror; 530, Laser output mirror. Detailed Implementation

[0034] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0035] In the description of the embodiments of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "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 the embodiments of the present invention 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 the embodiments of the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0036] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0037] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0038] In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples and features of different embodiments or examples described in this specification to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The following is combined with Figure 1 Figure 4(b) describes an end-side composite-pumped quasi-three-level laser according to an embodiment of the present invention. It should be understood that the following description is merely an illustrative embodiment of the present invention and does not constitute any particular limitation on the present invention.

[0040] An embodiment of the present invention provides a quasi-three-level laser with end-side composite pumping, such as... Figure 1 As shown, it includes: a quasi-three-level laser crystal 100; an end-face pumping assembly for emitting end-face pump light to the end face of the quasi-three-level laser crystal 100; a side-face pumping module 300 for emitting side-face pump light to the side of the quasi-three-level laser crystal 100; and a laser resonant cavity that cooperates with the quasi-three-level laser crystal 100 to cause the laser generated by the quasi-three-level laser crystal 100 to oscillate and be output within the laser resonant cavity.

[0041] In other words, the end-side pumped quasi-trilevel laser provided by this invention includes a quasi-trilevel laser crystal 100, an end-side pumping assembly, a side-side pumping module 300, and a laser resonator. The end-side pumping assembly provides end-side pump light, and the side-side pumping module 300 provides side-side pump light. The end-side pumping assembly is positioned corresponding to the end face of the quasi-trilevel laser crystal 100 to inject end-side pump light into the end face of the quasi-trilevel laser crystal 100. The side-side pumping module 300 is positioned corresponding to the side face of the quasi-trilevel laser crystal 100 to inject side-side pump light into the side face of the quasi-trilevel laser crystal 100. The laser resonator and the quasi-trilevel laser crystal 100 cooperate to form a laser oscillation circuit. The quasi-trilevel laser crystal 100 generates laser light under the synergistic excitation of the end-side pump light and the side-side pump light. The laser light oscillates within the laser resonator and is output outwards.

[0042] During operation, the end-face pumping component emits high-power-density end-face pump light to the end face of the quasi-three-level laser crystal 100, while the side-face pumping module 300 emits wide-coverage side-face pump light to the sides of the crystal. These two types of pump light are incident on the interior of the quasi-three-level laser crystal 100 from the end face and side face, respectively. The high power density provided by the end-face pump light satisfies the requirement of population inversion and clearing the lower energy levels of the quasi-three-level laser crystal 100, overcoming the high threshold characteristic of the crystal. Simultaneously, the side-face pump light distributes the heat load through a large-area irradiation, avoiding the localized heat accumulation problem caused by pure end-face pumping. Under the synergistic effect of the two types of pump light, the quasi-three-level laser crystal 100 is stimulated to generate laser light. The laser light enters the laser resonant cavity, undergoes multiple reflections and oscillations to achieve energy amplification, and finally forms a stable high-power laser light for output.

[0043] With this structural configuration, the end-pump assembly can provide high-power-density end-pump light to the quasi-trilevel laser crystal 100, precisely meeting the high-power-density excitation requirements for population inversion and ensuring effective establishment of population inversion and laser gain. The side-pump module 300 emits pump light from the side of the quasi-trilevel laser crystal 100, which can achieve uniform distribution of pump heat load, significantly reduce the temperature gradient inside the crystal, effectively suppress the thermal lensing effect, and significantly reduce the stress on the crystal end face. This achieves a balance between high-power-density excitation and low thermal stress and uniform heat distribution in the quasi-trilevel laser crystal 100, ensuring that the end-side-pumped quasi-trilevel laser can stably achieve high-power laser output.

[0044] In one embodiment of the present invention, the end-face pumping assembly includes: a first end-face pumping module 210 disposed at one end of the quasi-triple-level laser crystal 100; and a second end-face pumping module 220 disposed at the other end of the quasi-triple-level laser crystal 100. For example, both the first end-face pumping module 210 and the second end-face pumping module 220 are coupled to output via optical fiber.

[0045] The side-pumping module 300 includes: multiple semiconductor laser linear arrays, each of which is arranged in a ring around the side of the quasi-three-level laser crystal 100, and the irradiation length of the semiconductor laser linear arrays can cover the doped region of the quasi-three-level laser crystal 100.

[0046] In one embodiment of the present invention, the end-side composite pumped quasi-triple-level laser further includes: a first temperature control module, which is connected to the end-side pumping component and is used to adjust the temperature of the end-side pumping component so that the end-side pump light wavelength of the end-side pumping component deviates from the peak absorption wavelength of the 100-doped region of the quasi-triple-level laser crystal.

[0047] In one embodiment of the present invention, the end-side composite-pumped quasi-three-level laser further includes a second temperature control module, which includes a first cooling channel and a second cooling channel.

[0048] The first cooling channel is connected to the side pump module 300 and is used to adjust the temperature of the side pump module 300 so that the wavelength of the side pump light emitted by the side pump module 300 is aligned with the peak absorption wavelength of the doped region of the quasi-three-level laser crystal 100. The second cooling channel is connected to the quasi-three-level laser crystal 100 and is used to adjust the temperature of the quasi-three-level laser crystal 100 so as to reduce the particle number occupancy factor of the laser level of the quasi-three-level laser crystal 100.

[0049] In one embodiment of the present invention, the end-face-pumped quasi-triple-level laser further includes: a first beam shaping component 410, which is disposed between one end of the first end-face pumping module 210 and the quasi-triple-level laser crystal 100, and is used to collimate and focus the end-face pump light of the first end-face pumping module 210; and a second beam shaping component 420, which is disposed between the second end-face pumping module 220 and the other end of the quasi-triple-level laser crystal 100, and is used to collimate and focus the end-face pump light of the second end-face pumping module 220.

[0050] In one embodiment of the present invention, the laser resonant cavity includes: a first resonant cavity mirror 510 disposed between a first beam shaping component 410 and one end of a quasi-trilevel laser crystal 100; a second resonant cavity mirror 520 disposed between a second beam shaping component 420 and the other end of a quasi-trilevel laser crystal 100; and a laser output mirror 530, which together with the first resonant cavity mirror 510 and the second resonant cavity mirror 520 forms a laser resonant cavity, so that the laser generated by the quasi-trilevel laser crystal 100 under stimulation oscillates within the laser resonant cavity and is output from the laser output mirror 530.

[0051] In one embodiment of the present invention, the first resonant cavity mirror 510 and the second resonant cavity mirror 520 are plane mirrors or plano-concave mirrors.

[0052] The incident angle of the first resonant cavity mirror 510 is 0°, and the incident angle of the second resonant cavity mirror 520 is 45°. The first resonant cavity mirror 510, the second resonant cavity mirror 520 and the laser output mirror 530 together constitute an L-shaped laser resonant cavity.

[0053] Both the first resonant cavity mirror 510 and the second resonant cavity mirror 520 are coated with a bicolor film. The bicolor film is used to transmit end-face pump light and reflect the laser generated by the quasi-three-level laser crystal 100 under stimulation, so that the transmittance of the end-face pump light of the first resonant cavity mirror 510 and the second resonant cavity mirror 520 is not less than 98%, and the wavelength reflectivity of the output laser of the first resonant cavity mirror 510 and the second resonant cavity mirror 520 is not less than 99.5%.

[0054] The laser output mirror 530 has a laser transmittance of 10%-30%.

[0055] In one embodiment of the present invention, the quasi-three-level laser crystal 100 is a rod-shaped crystal.

[0056] The quasi-three-level laser crystal 100 is a ytterbium-doped laser crystal, or a thulium-doped laser crystal, or a holmium-doped laser crystal.

[0057] The two-terminal bond of the quasi-three-level laser crystal 100 is an undoped matrix crystal.

[0058] Furthermore, in one embodiment of the present invention, the quasi-three-level laser crystal 100 is a ytterbium-doped laser crystal; the undoped crystal in the same matrix is ​​a YAG crystal. Specifically, for example... Figure 1 As shown, the quasi-three-level laser crystal 100 has a rod-like structure and is selected from ytterbium-doped laser crystals, thulium-doped laser crystals, or holmium-doped laser crystals. For example, the quasi-three-level laser crystal 100 is a Yb:YAG crystal rod. This crystal rod adopts a bonding structure design, with both ends bonded to the same undoped YAG crystal matrix to reduce end-face thermal effects and increase the damage threshold.

[0059] More specifically, the length of the middle doped region of the rod-shaped crystal is 23 mm, the doping concentration is 2 at.%-3 at.%, the length of the undoped regions at both ends is 20 mm, the overall diameter of the rod-shaped crystal is 5 mm-5.5 mm, and its sides are coated with an anti-reflection film for the side pump light wavelength, which can reduce the reflection loss of pump light on the side of the crystal and significantly improve the pump light absorption efficiency.

[0060] The end-pump assembly includes a first end-pump module 210 and a second end-pump module 220, which are symmetrically arranged at both ends of the quasi-three-level laser crystal 100 to form a dual-end-pump layout. Both end-pump modules use fiber-coupled semiconductor lasers with a core diameter of 200μm-400μm and a numerical aperture of 0.22. Through fiber coupling, efficient transmission and precise focusing of pump light can be achieved, providing the crystal with high-power-density end-pump light.

[0061] The side-pumping module 300 is composed of multiple semiconductor laser linear arrays. Each of the semiconductor laser linear arrays is arranged in a ring around the side of the quasi-three-level laser crystal 100. The irradiation length of the semiconductor laser linear array can cover the doped region of the quasi-three-level laser crystal 100. Each semiconductor laser linear array includes multiple semiconductor lasers arranged sequentially along the axial direction of the quasi-three-level laser crystal 100.

[0062] A three-dimensional or five-dimensional surround distribution can be adopted to ensure that the output pump light has a certain divergence angle and that the irradiation length can completely cover the entire doped region of the quasi-three-level laser crystal 100, thereby achieving uniform pumping of the crystal side. The three-dimensional and five-dimensional dimensions referred to here are the number of semiconductor laser linear arrays.

[0063] The end-face-pumped quasi-trilevel laser also includes a first beam shaping component 410 and a second beam shaping component 420, which are precisely positioned corresponding to the two end-face pumping modules. Specifically, the first beam shaping component 410 is disposed between one end of the first end-face pumping module 210 and the quasi-trilevel laser crystal 100, and is used to collimate and focus the end-face pump light emitted by the first end-face pumping module 210. The second beam shaping component 420 is disposed between the other end of the second end-face pumping module 220 and the quasi-trilevel laser crystal 100, and is used to collimate and focus the end-face pump light emitted by the second end-face pumping module 220.

[0064] Both beam shaping components consist of collimating lenses and focusing lenses. By optimizing the focal length combination of the collimating lenses and focusing lenses, different beam expansion ratios can be achieved. Ultimately, the end-face pump light is focused to form a pump spot with a diameter of 1.6mm-3.2mm, which is precisely adapted to the end-face size of the quasi-three-level laser crystal 100. This ensures that the pump light is incident on the end-face of the crystal with high power density, providing a sufficient energy basis for population inversion.

[0065] The laser resonant cavity includes a first resonant cavity mirror 510, a second resonant cavity mirror 520, and a laser output mirror 530. The first resonant cavity mirror 510 is disposed between the first beam shaping component 410 and one end of the quasi-three-level laser crystal 100, and the second resonant cavity mirror 520 is disposed between the second beam shaping component 420 and the other end of the quasi-three-level laser crystal 100, ensuring that the end-face pump light can be smoothly transmitted to the rod-shaped crystal after beam shaping, while the laser can oscillate efficiently within the resonant cavity.

[0066] The first resonant cavity mirror 510 and the second resonant cavity mirror 520 can be plane mirrors or plano-concave mirrors. For example, Figure 1 As shown, the incident angle of the first resonant cavity mirror 510 is 0°, and the incident angle of the second resonant cavity mirror 520 is 45°. Together with the laser output mirror 530, they form an L-shaped laser resonant cavity. This cavity structure is compact and can effectively avoid mutual interference between the pump light path and the laser oscillation light path, thus improving the stability of the optical path. Both the first resonant cavity mirror 510 and the second resonant cavity mirror 520 are coated with a bicolor film, which can ensure low-loss transmission of the end-face pump light to the crystal, while efficiently reflecting the laser generated by the crystal under stimulation. The transmittance of the end-face pump light for both the first resonant cavity mirror 510 and the second resonant cavity mirror 520 is not less than 98%, and the reflectance of the output laser is not less than 99.5%. The transmittance of the laser for the laser output mirror 530 is 10%-30%, which can ensure that the laser oscillates and amplifies sufficiently within the resonant cavity, and achieve stable power output.

[0067] The end-side composite-pumped quasi-three-level laser is also equipped with an independent first temperature control module and a second temperature control module.

[0068] The first temperature control module is connected to the end-face pump assembly and uses circulating water cooling to achieve heat dissipation and wavelength control. For example, by precisely adjusting the cooling water temperature, the wavelength of the end-face pump light emitted by the first and second end-face pump modules 220 is stabilized at 938nm or 941nm, which is slightly deviated from the peak absorption wavelength of 940nm of the quasi-triple-level laser crystal 100 (such as Yb:YAG). This structural design effectively increases the penetration depth of the end-face pump light in the crystal, avoids local heat concentration caused by the pump energy being concentrated at the end face, makes the heat distribution inside the crystal more uniform, and ensures effective absorption of the pump light.

[0069] The second temperature control module is a dual-channel cooling structure, comprising an independent first cooling channel and a second cooling channel, both employing circulating water cooling to achieve precise temperature control for different components. The first cooling channel is connected to the side pump module 300, with a temperature adjustment range of 15℃-28℃. By flexibly adjusting the water temperature within this range, the emission wavelength of the semiconductor laser in the side pump module 300 can be precisely aligned with the peak absorption wavelength of the quasi-triple-level laser crystal 100 (e.g., 940nm for Yb:YAG), ensuring efficient absorption of the side pump light by the crystal, improving pump efficiency, and preventing insufficient absorption of pump light due to wavelength shift, which would otherwise be converted into additional heat load. The second cooling channel is connected to the quasi-triple-level laser crystal 100, with a temperature adjustment range of 5℃-18℃. By stabilizing the crystal temperature within this low-temperature range, the population occupancy factor of the laser's lower energy level can be significantly reduced, decreasing reabsorption losses and providing favorable conditions for the crystal to establish effective population inversion, thereby improving the generation efficiency of the quasi-triple-level laser.

[0070] During the specific operation, the first temperature control module and the second temperature control module are activated. The first temperature control module adjusts the cooling water temperature of the end-face pump assembly, so that the first and second end-face pump modules 220 emit end-face pump light with wavelengths of 938nm or 941nm respectively, ensuring that it deviates slightly from the peak absorption wavelength of the crystal. The second temperature control module adjusts the temperature of the side pump module 300 to 15℃-28℃ through the first cooling channel, so that it emits side pump light with a wavelength of 940nm. At the same time, the second cooling channel stabilizes the temperature of the quasi-three-level laser crystal 100 at 5℃-18℃, reducing the lower level particle occupancy factor.

[0071] The pump light from the first end-face pump module 210 is collimated and focused by the first beam shaping component 410, and then shines through the bicolor film of the first resonant cavity mirror 510 onto one end face of the quasi-triple-level laser crystal 100. The pump light from the second end-face pump module 220 is collimated and focused by the second beam shaping component 420, and then shines through the bicolor film of the second resonant cavity mirror 520 onto the other end face of the quasi-triple-level laser crystal 100. Simultaneously, the pump light emitted by the side pump module 300 uniformly illuminates the side surface of the crystal and completely covers the entire doped region.

[0072] The high-power-density spot formed by the end-face pump light after beam shaping, and the increased penetration depth makes the energy distribution more uniform; the side pump light provides sufficient pump power through wide-area uniform irradiation, and the efficient absorption characteristics reduce ineffective heat load; combined with the low-temperature environment of the crystal to suppress the number of particles in the lower energy level, the three work together to form a uniform and sufficient inverted particle number density inside the crystal, effectively overcoming reabsorption loss, and the crystal generates laser light under stimulation.

[0073] The laser generated by the crystal under stimulation enters the L-shaped laser resonant cavity, and under the high reflection of the first resonant cavity mirror 510 and the second resonant cavity mirror 520, it oscillates and amplifies repeatedly, and finally outputs a stable laser through the laser output mirror 530. In this embodiment, the output laser wavelength is 1030nm.

[0074] To fully verify the technical effect of the present invention, this embodiment sets the total pump power to 1600W and compares and simulates the traditional end-face pump, the traditional side-face pump, and the end-side composite pump structure of the present invention.

[0075] Regarding the optimization effect of temperature field distribution: As shown in Figure 2(a), the pump light of the traditional end-face pumping structure is concentrated in the center of the crystal end face, resulting in a large temperature gradient inside the crystal and a significantly higher local temperature, which easily leads to a severe thermal lensing effect; As shown in Figure 2(b), in the structure of the present invention, the side pumping effectively shares most of the pump power, the overall temperature of the crystal is significantly reduced, the temperature distribution uniformity is greatly improved, and the thermal lensing effect is effectively alleviated.

[0076] Regarding the optimization effect of stress field distribution: As shown in Figure 3(a), in the traditional end-face pumping structure, the stress values ​​at the edges of the two incident crystal faces are extremely high, close to the crystal fracture threshold, posing a great risk of cracking and severely limiting the further improvement of pump power; As shown in Figure 3(b), the structure of the present invention significantly reduces the maximum stress of the crystal by distributing the heat load of the side pump, and the stress distribution is more uniform. Under the same fracture threshold conditions, it can support higher pump power input.

[0077] Regarding the effect of inverted particle number density and beam quality improvement: As shown in Figure 4(a), the cumulative inverted particle number density of the traditional side-pumped structure is extremely low, which is insufficient to provide the required small signal gain and makes it difficult to achieve effective laser output; As shown in Figure 4(b), the structure of the present invention combines the advantages of high power density of end-pumping and uniform excitation of side-pumping, which not only provides sufficient inverted particle number density to overcome reabsorption loss, but also achieves good spatial matching, which helps to ultimately achieve high-efficiency and high-beam-quality laser output.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quasi-three-level laser with end-side composite pumping, characterized in that, The end-side composite-pumped quasi-three-level laser includes: Quasi-three-level laser crystal (100); An end-pumping assembly is used to emit end-pumping light onto the end face of the quasi-three-level laser crystal (100); A side pump module (300) is used to emit side pump light to the side of the quasi-three-level laser crystal (100); A laser resonant cavity is provided, which is used in conjunction with the quasi-three-level laser crystal (100) to cause the laser generated by the quasi-three-level laser crystal (100) to oscillate and be output within the laser resonant cavity.

2. The end-side-pumped quasi-three-level laser according to claim 1, characterized in that, The end-face pump assembly includes: A first end-face pump module (210) is disposed at one end of the quasi-three-level laser crystal (100); The second end-face pump module (220) is disposed at the other end of the quasi-three-level laser crystal (100); The side pump module (300) includes: Multiple semiconductor laser arrays are arranged in a ring around the side of the quasi-three-level laser crystal (100), and the irradiation length of the semiconductor laser arrays can cover the doped region of the quasi-three-level laser crystal (100).

3. The end-side-pumped quasi-three-level laser according to claim 2, characterized in that, The end-side composite-pumped quasi-three-level laser also includes: A first temperature control module, which is connected to the end-face pump assembly, is used to adjust the temperature of the end-face pump assembly so that the wavelength of the end-face pump light of the end-face pump assembly deviates from the peak absorption wavelength of the doped region of the quasi-three-level laser crystal (100). The second temperature control module includes a first cooling channel and a second cooling channel; The first cooling channel is connected to the side pump module (300) and is used to adjust the temperature of the side pump module (300) so that the wavelength of the side pump light emitted by the side pump module (300) is aligned with the peak absorption wavelength of the doped region of the quasi-three-level laser crystal (100). The second cooling channel is connected to the quasi-three-level laser crystal (100) and is used to adjust the temperature of the quasi-three-level laser crystal (100) to reduce the particle number occupancy factor of the laser level of the quasi-three-level laser crystal (100).

4. The end-side-pumped quasi-three-level laser according to claim 2, characterized in that, The end-side composite-pumped quasi-three-level laser also includes: The first beam shaping component (410) is disposed between the first end face pump module (210) and one end of the quasi-three-level laser crystal (100), and is used to collimate and focus the end face pump light of the first end face pump module (210). The second beam shaping component (420) is disposed between the second end face pump module (220) and the other end of the quasi-three-level laser crystal (100), and is used to collimate and focus the end face pump light of the second end face pump module (220).

5. The end-side-pumped quasi-three-level laser according to claim 4, characterized in that, The laser resonant cavity includes: A first resonant cavity mirror (510) is disposed between the first beam shaping component (410) and one end of the quasi-three-level laser crystal (100); The second resonant cavity mirror (520) is disposed between the second beam shaping component (420) and the other end of the quasi-three-level laser crystal (100); A laser output mirror (530) is provided, which together with the first resonant cavity mirror (510) and the second resonant cavity mirror (520) form a laser resonant cavity, so that the laser generated by the quasi-three-level laser crystal (100) is stimulated to oscillate in the laser resonant cavity and output from the laser output mirror (530).

6. The end-side-pumped quasi-three-level laser according to claim 5, characterized in that, The first resonant cavity mirror (510) and the second resonant cavity mirror (520) are plane mirrors or plano-concave mirrors; The incident angle of the first resonant cavity mirror (510) is 0°, and the incident angle of the second resonant cavity mirror (520) is 45°. The first resonant cavity mirror (510), the second resonant cavity mirror (520) and the laser output mirror (530) together constitute an L-shaped laser resonant cavity. Both the first resonant cavity mirror (510) and the second resonant cavity mirror (520) are coated with a dual-color film so that the transmittance of the first resonant cavity mirror (510) and the second resonant cavity mirror (520) to the end face pump light is not less than 98%, and the wavelength reflectance of the first resonant cavity mirror (510) and the second resonant cavity mirror (520) to the output laser is not less than 99.5%. The laser output mirror (530) has a laser transmittance of 10%-30%.

7. The end-side-pumped quasi-three-level laser according to claim 1, characterized in that, The quasi-three-level laser crystal (100) is a rod-shaped crystal; The quasi-three-level laser crystal (100) is a ytterbium-doped laser crystal, or a thulium-doped laser crystal, or a holmium-doped laser crystal; The quasi-three-level laser crystal (100) has an undoped matrix with two-terminal bonds.

8. The end-side-pumped quasi-three-level laser according to claim 7, characterized in that, The quasi-three-level laser crystal (100) is a ytterbium-doped laser crystal; The undoped crystal in the same matrix is ​​a YAG crystal.

9. The end-side-pumped quasi-three-level laser according to claim 3, characterized in that, The temperature adjustment range of the first cooling channel is 15℃-28℃; The temperature adjustment range of the second cooling channel is 5℃-18℃.

10. The end-side-pumped quasi-three-level laser according to claim 2, characterized in that, Both the first end-face pump module (210) and the second end-face pump module (220) are output via optical fiber coupling.

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