Solid laser with gain medium with periodic chromium-doped structure

Abstract

The utility model provides a solid laser with a periodic chromium-doped structure gain medium. The solid laser comprises a pumping source, a pumping coupling device, a laser resonant cavity input end cavity mirror, a laser gain medium and a laser resonant cavity output coupling mirror which are arranged in sequence, the pumping source is used for emitting pumping light with the wavelength capable of being absorbed by the laser gain medium; the pumping coupling device is used for collimating and focusing the pumping light emitted by the pumping source into the laser gain medium; the laser resonant cavity input end cavity mirror is used for passing through the pump light and reflecting the laser emitted by the laser gain medium; the laser gain medium is a blocky solid gain medium with a chromium-doped structure, and the chromium-doped concentration of the laser gain medium changes periodically; and the laser resonant cavity output coupling mirror is used for partially transmitting the laser emitted by the laser gain medium. The structure with the doping concentration changing periodically in the laser gain medium can effectively relieve the heat effect generated by the gain medium under the excitation of the pump light, so as to realize the stable output of the laser.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a solid-state laser with a periodic chromium-doped gain medium. Background Technology

[0002] For solid-state lasers based on bulk crystals, thermal management of the solid gain medium is a key issue in order to achieve stable, efficient, high-power, and high-beam-quality laser output. Effective thermal management can achieve efficient heat dissipation and uniform heat distribution within the gain medium. In addition to strengthening the effective contact between the gain medium and the heat sink to reduce thermal resistance, designing the configuration of the gain medium itself is also a very effective method. For example, using bonded crystal, thin-film crystal, or slab crystal configurations as the gain medium within the laser.

[0003] Bonded crystal configuration refers to bonding two undoped crystals together on the two light-transmitting end faces of a rod-shaped doped crystal. This enhances heat dissipation from the end faces, reduces end face deformation, and lowers the possibility of thermal damage. However, bonded crystals have high requirements for crystal processing and bonding technology, resulting in high manufacturing costs. In addition, the performance improvement is relatively limited due to the limitation of the bonding surface.

[0004] Thin-plate crystal configurations refer to gain media whose length along the light-transmitting direction is much smaller than the width of the light-transmitting surface. Typically, the gain media thickness is several hundred micrometers, while the light-transmitting surface size can reach the centimeter scale. Because it utilizes the light-transmitting surface for heat dissipation, the heat conduction distance is short, resulting in rapid heat dissipation. Furthermore, the pump light size is close to the light-transmitting surface size, leading to a very uniform pump light distribution and reducing various thermal distortions caused by uneven thermal distribution. This configuration is suitable for high-power ultrashort pulse lasers. However, the fabrication of thin-plate configurations is difficult, and related technologies have not yet been fully mastered in China, resulting in high costs. The corresponding pump structures are also very complex and bulky.

[0005] A slab crystal configuration refers to a gain medium that is elongated and narrow. One dimension of the light-transmitting surface is very small, approximately millimeters, while the other dimension is much larger, ranging from centimeters to several centimeters. The light transmission length is relatively long, approximately on the order of centimeters. The pump light in a slab configuration is distributed throughout the entire slab, utilizing the large side surface parallel to the light transmission direction for heat dissipation. Therefore, it resembles a thin-plate structure, resulting in short heat conduction distances, rapid heat dissipation, and reduced heat deposition within the medium, enabling high-power output. However, slab structures are complex to fabricate, and their biggest challenge is the poor quality of the output laser beam. This makes them more suitable for laser amplification than for laser oscillators.

[0006] It is evident that the heat dissipation structure of solid-state lasers based on bulk crystals in related technologies faces challenges such as high implementation difficulty, complex structure, and high cost. Utility Model Content

[0007] The technical objective of this invention is to provide a solid-state laser with a periodic chromium-doped gain medium, which can effectively alleviate the thermal effect generated by the gain medium under pump light excitation, thereby achieving stable laser output.

[0008] To solve the above-mentioned technical problems, this utility model is implemented as follows: a solid-state laser with a periodic chromium-doped gain medium includes a pump source, a pump coupling device, a laser resonator input end cavity mirror, a laser gain medium, and a laser resonator output coupling mirror arranged in sequence.

[0009] The pump source is used to emit pump light of a wavelength that can be absorbed by the laser gain medium.

[0010] The pump coupling device is used to collimate and focus the pump light emitted by the pump source into the interior of the laser gain medium.

[0011] The laser resonator input end mirror is used to transmit the pump light and reflect the laser emitted by the laser gain medium;

[0012] The laser gain medium is a chromium-doped bulk solid gain medium with a periodic variation in chromium doping concentration.

[0013] The laser resonator output coupling mirror is used to partially transmit the laser emitted through the laser gain medium;

[0014] The laser resonant cavity input end cavity mirror and the laser resonant cavity output coupling mirror form a resonant cavity, which provides positive feedback for laser oscillation and is used to select the wavelength of the generated laser and output the laser.

[0015] Furthermore, the laser gain medium is a divalent chromium ion-doped II-VI group semiconductor material.

[0016] Furthermore, the laser gain medium is a chromium-doped zinc selenide crystal Cr:ZnSe;

[0017] Alternatively, the laser gain medium is a chromium-doped zinc sulfide crystal Cr:ZnS;

[0018] Alternatively, the laser gain medium is a chromium-doped cadmium selenide crystal Cr:CdSe.

[0019] Furthermore, the chromium doping method of the laser gain medium starts with doping at the pump light input end and ends with no doping at the output end;

[0020] Alternatively, the chromium doping method of the laser gain medium is such that it starts with no doping at the input end of the pump light and ends with doping at the output end;

[0021] Alternatively, the chromium doping method of the laser gain medium is to dopant at both ends and leave the middle undoped;

[0022] Alternatively, the chromium doping method of the laser gain medium is central doping with no doping at both ends.

[0023] Furthermore, the shape of the light-transmitting surface of the laser gain medium is square, triangular, elliptical, or circular.

[0024] Furthermore, the complete doping period of the laser gain medium is greater than or equal to 2;

[0025] The length period of periodic doping is uniform: within one length period, the length of the doped region is equal to the length of the undoped region;

[0026] Alternatively, the length period of the periodic doping is non-uniform: within a length period, the length of the doped region is not equal to the length of the undoped region, or the total length of different periods is also different.

[0027] Furthermore, the lens types of the laser resonator input end cavity mirror and the laser resonator output coupling mirror are any one of the following: flat-flat, flat-concave, and concave-flat lenses.

[0028] Furthermore, the resonant cavity structure formed by the laser resonant cavity input end cavity mirror and the laser resonant cavity output coupling mirror is any one of the following: FP cavity, folded cavity, or ring cavity.

[0029] Furthermore, it also includes a first reflecting mirror located between the laser gain medium and the laser resonator output coupling mirror. The first reflecting mirror is used to reflect the laser output from the laser gain medium to the laser resonator output coupling mirror, wherein the reflectivity of the first reflecting mirror to the laser emitted by the laser gain medium is not less than 99%.

[0030] Furthermore, it also includes a first reflecting mirror and a second reflecting mirror located between the optical path of the laser gain medium and the output coupling mirror of the laser resonator. The first reflecting mirror is used to reflect the laser output by the laser gain medium, and the second reflecting mirror is used to receive the laser reflected by the first reflecting mirror and reflect it to the output coupling mirror of the laser resonator. The input end cavity mirror of the laser resonator is also used to reflect the laser emitted by the laser gain medium to the output coupling mirror of the laser resonator. The reflectivity of the first reflecting mirror and the second reflecting mirror to the laser emitted by the laser gain medium is not less than 99%.

[0031] Compared with existing technologies, the solid-state laser with a periodic chromium-doped gain medium in this invention has the following advantages:

[0032] The pump light emitted by the pump source is collimated and focused into the laser gain medium by the pump coupling device. The laser resonator cavity consists of the input cavity mirror, the laser gain medium, and the output coupling mirror. The laser gain medium is a periodically chromium-doped block solid gain medium that receives the focused pump light and generates laser light under the excitation of the focused pump light, thus outputting laser light in the 2-3 μm band. The doping concentration in the laser gain medium varies periodically, with alternating doped and undoped regions containing chromium ions. The undoped regions do not absorb pump light energy and do not actively generate heat, thus acting as a heat-conducting medium to help dissipate heat in the doped regions. This effectively alleviates the thermal effect generated by the gain medium under pump light excitation, thereby achieving stable laser output. It has the advantages of low implementation difficulty, simple structure, and low cost. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of a solid-state laser based on a gain medium with a periodic chromium-doped structure, as described in this embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a mid-infrared solid-state laser with a periodic chromium-doped gain medium composed of a three-mirror folded cavity in an embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a mid-infrared solid-state laser with a periodic chromium-doped gain medium consisting of a ring cavity as the resonant cavity in this embodiment of the present invention.

[0036] Figure 4 This is an alternative scheme for the periodic chromium-doped gain medium in the embodiments of this utility model. Detailed Implementation

[0037] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model.

[0038] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "circumferential", "radial", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0039] 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 utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0040] Combination Figure 1-3 A solid-state laser with a periodically chromium-doped gain medium is provided, comprising a pump source 1, a pump coupling device 2, a laser resonator input mirror 3, a laser gain medium 4, and a laser resonator output mirror 5 arranged sequentially. The pump source 1 emits pump light of a wavelength that can be absorbed by the laser gain medium 4. The pump coupling device 2 collimates and focuses the pump light emitted by the pump source 1 into the laser gain medium 4. The laser resonator input mirror 3 transmits and reflects the laser emitted by the laser gain medium 4. The laser gain medium 4 is a chromium-doped block solid gain medium with a periodically varying chromium doping concentration. The laser resonator output mirror 5 partially transmits the laser emitted by the laser gain medium 4. The laser resonator input mirror 3 and the laser resonator output mirror 5 form a resonator, providing positive feedback for laser oscillation and wavelength selection of the generated laser for output laser.

[0041] In this scheme, the pump light emitted by the pump source 1 is collimated and focused into the laser gain medium 4 by the pump coupling device 2. The laser resonator input end cavity mirror 3, the laser gain medium 4, and the laser resonator output coupling mirror 5 constitute the resonator cavity. The laser gain medium 4 is a blocky solid gain medium with a periodic chromium-doped structure. It is used to receive the focused pump light and generate laser light under the excitation of the focused pump light, thereby outputting laser light in the 2-3μm band. The doping concentration in the laser gain medium 4 is periodically varied, that is, the doped regions containing chromium ions and the undoped regions are arranged alternately. The undoped regions do not absorb pump light energy and do not actively generate heat. Therefore, as a heat-conducting medium, it helps dissipate heat in the doped regions and can effectively alleviate the thermal effect generated by the gain medium under the excitation of pump light, so as to achieve stable laser output. It has the advantages of low implementation difficulty, simple structure, and low cost.

[0042] Furthermore, the laser gain medium 4 is a group III-VI semiconductor material doped with divalent chromium ions (Cr2+). The laser gain medium 4 can be a chromium-doped zinc selenide crystal (Cr:ZnSe); or, a chromium-doped zinc sulfide crystal (Cr:ZnS); or, a chromium-doped cadmium selenide crystal (Cr:CdSe). Group III-VI semiconductor materials doped with divalent chromium ions (Cr2+), with Cr:ZnSe / S / CdSe as a typical example, possess characteristics such as no excited-state absorption and near 100% room-temperature fluorescence quantum efficiency. In addition, their ultra-wideband emission spectrum covers the wavelength range from 2 micrometers to 3 micrometers, supporting the generation of mid-infrared periodic-level ultrashort pulses and wide-range tunable lasers. However, materials like Cr:ZnSe / S / CdSe have a large temperature gradient coefficient of refractive index, which can lead to a severe thermal lensing effect under high-power pumping, causing the laser cavity to become unstable and unable to output laser light. In this scheme, the structure in which the doping concentration in the laser gain medium 4 changes periodically can effectively alleviate the thermal effect generated by the gain medium under pump light excitation.

[0043] Furthermore, the chromium doping method of the laser gain medium 4 can be such that doping begins at the pump light input end and ends at the output end without doping. This method is beneficial for increasing pump absorption and improving efficiency under low-power pumping. Alternatively, the chromium doping method of the laser gain medium 4 can be such that doping begins at the pump light input end without doping and ends at the output end with doping. This method helps to increase the heat dissipation channel in the region where pump light absorption is strongest. Alternatively, the chromium doping method of the laser gain medium 4 can be such that both ends are doped and the middle is undoped. This method is suitable for simultaneous pumping at both ends. Alternatively, the chromium doping method of the laser gain medium 4 can be such that doping occurs in the middle and both ends are undoped. This method maximizes the increase in heat dissipation channel in the doped region.

[0044] In some embodiments, combined with Figure 4 The laser gain medium 4 can be provided with multiple chromium-doped segments along its length, with the portion between adjacent chromium-doped segments being undoped.

[0045] Furthermore, the shape of the light-transmitting surface of the laser gain medium 4 can be square, triangular, elliptical, or circular, etc.

[0046] Furthermore, the complete doping period of the laser gain medium 4 is greater than or equal to 2. The length period of the periodic doping is uniform: within one length period, the length of the doped region is equal to the length of the undoped region; or the length period of the periodic doping is non-uniform: within one length period, the length of the doped region is not equal to the length of the undoped region, or the total length of different periods is also different.

[0047] Furthermore, the lens types of the laser resonator input end cavity mirror 3 and the laser resonator output coupling mirror 5 are any one of the following: flat-flat, flat-concave, and concave-flat lenses.

[0048] Furthermore, the resonant cavity structure formed by the laser resonant cavity input end cavity mirror 3 and the laser resonant cavity output coupling mirror 5 can be any one of the following: FP cavity, folded cavity, or ring cavity.

[0049] This scheme provides three examples of solid-state lasers with periodic chromium-doped gain media, as follows:

[0050] Example 1:

[0051] like Figure 1 As shown, in this example, the pump source 1, pump coupling device 2, laser resonator input mirror 3, laser gain medium 4, and laser resonator output coupling mirror 5 are arranged sequentially in a straight line. The pump source 1 is used to emit pump light of a wavelength that can be absorbed by the laser gain medium 4; the pump coupling device 2 is used to collimate and focus the pump light emitted by the pump source 1 into the laser gain medium 4; the laser resonator input mirror 3 is used to transmit the pump light and reflect the laser emitted by the laser gain medium 4; the laser gain medium 4 is a chromium-doped block solid gain medium with a periodically varying chromium doping concentration, which can effectively alleviate the thermal effect generated by the gain medium under pump light excitation; the laser resonator output coupling mirror 5 is used to partially transmit the laser emitted by the laser gain medium 4; wherein, the laser resonator input mirror 3 and the laser resonator output coupling mirror 5 form an FP resonator, which provides positive feedback for laser oscillation and is used to perform wavelength selection on the generated laser and output the laser.

[0052] Example 2:

[0053] like Figure 2As shown, in this example, compared with Example 1, a first reflecting mirror 6 is also included, located between the optical path of the laser gain medium 4 and the laser resonator output coupling mirror 5. The first reflecting mirror 6 is used to reflect the laser output from the laser gain medium 4 to the laser resonator output coupling mirror 5. The reflectivity of the first reflecting mirror to the laser emitted from the laser gain medium 4 is not less than 99%.

[0054] Specifically, the pump source 1, pump coupling device 2, laser resonator input mirror 3, laser gain medium 4, and first reflecting mirror 6 are arranged in a straight line, while the laser resonator output coupling mirror 5 is located to the side. Therefore, the laser resonator input mirror 3, laser gain medium 4, first reflecting mirror 6, and laser resonator output coupling mirror 5 together constitute a folded resonator. The pump light emitted from the pump source 1 passes through the pump coupling device 2, is collimated and focused by the pump coupling device 2, and then acts on the periodically chromium-doped solid laser gain medium 4 through the laser resonator input mirror 3. Under the action of the focused pump light, the periodically chromium-doped solid laser gain medium 4 undergoes population inversion, thereby generating laser light. The generated laser light is oscillated and reflected by the laser resonator input mirror 3, first reflecting mirror 6, and laser resonator output coupling mirror 5 before being output through the laser coupling output mirror. In this folded cavity, the laser resonator input mirror 3 and laser resonator output coupling mirror 5 can allow the high transmittance of the laser light provided by the pump source 1 to pass through, and can reflect the high reflectivity of the laser light emitted by the laser gain medium 4. The laser gain medium 4 is a blocky solid gain medium with a periodic chromium-doped structure. It is used to receive the focused pump light and generate laser light under the excitation of the focused pump light. Both its front and rear end faces can allow the pump source 1 and the laser light emitted by itself to pass through with high transmittance. Moreover, this structure with periodic doping concentration can effectively alleviate the thermal effect generated by the gain medium under the excitation of pump light.

[0055] Example 3:

[0056] like Figure 3 As shown, in this example, compared to Example 1, it also includes a first reflecting mirror 6 and a second reflecting mirror 7 located between the optical path of the laser gain medium 4 and the laser resonator output coupling mirror 5. The first reflecting mirror 6 is used to reflect the laser output from the laser gain medium 4, and the second reflecting mirror 7 is used to receive the laser reflected by the first reflecting mirror 6 and reflect it to the laser resonator output coupling mirror 5. The laser resonator input end cavity mirror 3 is also used to reflect the laser emitted by the laser gain medium 4 to the laser resonator output coupling mirror 5. The reflectivity of the first reflecting mirror and the second reflecting mirror to the laser emitted by the laser gain medium 4 is not less than 99%.

[0057] Specifically, the pump source 1, pump coupling device 2, laser resonator input mirror 3, laser gain medium 4, and first reflecting mirror 6 are arranged in a straight line, while the second reflecting mirror 7 and laser resonator output coupling mirror 5 are located on the side. The laser resonator input mirror 3, laser gain medium 4, first reflecting mirror 6, second reflecting mirror 7, and laser resonator output coupling mirror 5 together constitute a ring resonator.

[0058] The pump light emitted from pump source 1 passes through pump coupling device 2, where it is collimated and focused. After passing through laser resonator input mirror 3, it acts on the periodically chromium-doped solid laser gain medium 4. Under the focused pump light, the periodically chromium-doped solid laser gain medium 4 undergoes population inversion, thereby generating laser light. The generated laser light is oscillated and reflected by laser resonator input mirror 3, first reflecting mirror 6, and laser resonator output coupling mirror 5, and then output through laser coupling output mirror 7. The laser resonator input mirror 3, laser resonator output coupling mirror 5, and second reflecting mirror 7 in this ring resonator are characterized by high transmittance of the laser light provided by pump source 1 and high reflectivity of the laser light emitted by laser gain medium 4. The laser gain medium 4 is characterized as a blocky solid gain medium with a periodic chromium-doped structure. It is used to receive the focused pump light and generate laser light under the excitation of the focused pump light. Both its front and rear end faces can allow the pump source 1 and the laser light emitted by itself to pass through with high transmittance. Moreover, this structure with periodic variation in doping concentration can effectively alleviate the thermal effect generated by the gain medium under the excitation of pump light.

[0059] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A solid-state laser with a periodic chromium-doped gain medium, characterized in that, It includes, in sequence, a pump source, a pump coupling device, a laser resonator input end cavity mirror, a laser gain medium, and a laser resonator output coupling mirror; The pump source is used to emit pump light of a wavelength that can be absorbed by the laser gain medium. The pump coupling device is used to collimate and focus the pump light emitted by the pump source into the interior of the laser gain medium. The laser resonator input end mirror is used to transmit the pump light and reflect the laser emitted by the laser gain medium; The laser gain medium is a chromium-doped zinc selenide crystal Cr:ZnSe, or a chromium-doped zinc sulfide crystal Cr:ZnS, or a chromium-doped cadmium selenide crystal Cr:CdSe, and the laser gain medium contains alternating doped and undoped regions of chromium ions. The laser resonator output coupling mirror is used to partially transmit the laser emitted through the laser gain medium; The laser resonant cavity input end cavity mirror and the laser resonant cavity output coupling mirror form a resonant cavity, which provides positive feedback for laser oscillation and is used to select the wavelength of the generated laser and output the laser.

2. The solid-state laser with a periodic chromium-doped gain medium according to claim 1, characterized in that, The shape of the light-transmitting surface of the laser gain medium is square, triangular, elliptical, or circular.

3. The solid-state laser with a periodic chromium-doped gain medium according to any one of claims 1-2, characterized in that, The complete doping period of the laser gain medium is greater than or equal to 2; Within one length period, the length of the doped region is equal to the length of the undoped region; Alternatively, within a single period, the length of the doped region may not be equal to the length of the undoped region, or the total length of different periods may also be different.

4. The solid-state laser with a periodic chromium-doped gain medium according to claim 3, characterized in that, The lens types of the laser resonator input end cavity mirror and the laser resonator output coupling mirror are any one of the following: flat-flat, flat-concave, and concave-flat lenses.

5. The solid-state laser with a periodic chromium-doped gain medium according to claim 3, characterized in that, The resonant cavity structure formed by the laser resonant cavity input end cavity mirror and the laser resonant cavity output coupling mirror can be any one of the following: FP cavity, folded cavity, or ring cavity.

6. The solid-state laser with a periodic chromium-doped gain medium according to claim 3, characterized in that, It also includes a first reflecting mirror located between the laser gain medium and the laser resonator output coupling mirror. The first reflecting mirror is used to reflect the laser output from the laser gain medium to the laser resonator output coupling mirror. The reflectivity of the first reflecting mirror to the laser emitted from the laser gain medium is not less than 99%.

7. The solid-state laser with a periodic chromium-doped gain medium according to claim 3, characterized in that, It also includes a first reflecting mirror and a second reflecting mirror located between the laser gain medium and the laser resonator output coupling mirror. The first reflecting mirror is used to reflect the laser output by the laser gain medium, and the second reflecting mirror is used to receive the laser reflected by the first reflecting mirror and reflect it to the laser resonator output coupling mirror. The laser resonator input end cavity mirror is also used to reflect the laser emitted by the laser gain medium to the laser resonator output coupling mirror. The reflectivity of the first reflecting mirror and the second reflecting mirror to the laser emitted by the laser gain medium is not less than 99%.

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