Solid state laser

Abstract

The embodiment of the invention provides a solid laser, which comprises a gain resonant cavity and a loss resonant cavity connected with the gain resonant cavity, the gain resonant cavity comprises a first cavity and a gain medium assembly arranged in the first cavity, and is used for reflecting light of the gain resonant cavity back and forth in the cavity to prolong the working length of the gain medium assembly, inhibiting spontaneous radiation of photons and improving the photon number density in the cavity; wherein the gain medium assembly is used for providing optical gain; and the loss resonant cavity comprises a second cavity and a lens system arranged in the second cavity, and is used for reducing the diffraction loss of the auxiliary resonant cavity. According to the solid laser, the composite degenerate cavity structure design is adopted, the main body gain resonant cavity and the auxiliary loss resonant cavity are separated, and the quality of output light beams is improved.

Description

Technical Field

[0001] The present application relates to the technical field of laser design, and in particular to a solid-state laser. Background Art

[0002] Currently, it is difficult to balance the multi-mode competition of short-cavity lasers and the diffraction loss of long-cavity lasers, resulting in a high lasing threshold and poor beam quality in the laser output. To address the lasing threshold, the usual approach is to reduce diffraction loss through cavity structure design, but this approach reduces the loss interval of the mode, resulting in multi-mode oscillation and reduced beam quality. To address beam quality, the usual approach is to compress the laser oscillation mode and achieve fundamental mode oscillation and output of the laser through the selection of the transverse mode, thereby obtaining good directivity. However, this approach greatly reduces the effective utilization of the gain medium activation area. Summary of the Invention

[0003] The purpose of the present application is to provide a solid-state laser that can adopt a composite degenerate cavity structure design to separate the main gain resonant cavity and the auxiliary loss resonant cavity, so as to improve the quality of the output light beam.

[0004] In a first aspect, the present invention provides a solid-state laser, comprising: a gain resonant cavity and a loss resonant cavity connected to the gain resonant cavity; the gain resonant cavity comprises a first cavity and a gain medium component disposed in the first cavity, the gain resonant cavity being used to extend the working length of the gain medium component by reflecting light of the gain resonant cavity back and forth in the cavity, suppress spontaneous emission of photons, and increase the photon number density in the cavity; wherein the gain medium component is used to provide optical gain; the loss resonant cavity comprises a second cavity and a lens system disposed in the second cavity, the loss resonant cavity being used to reduce the diffraction loss of the auxiliary resonant cavity.

[0005] In the above implementation method, a separate main gain resonant cavity and an auxiliary loss resonant cavity can be designed. The main gain resonant cavity can reduce the insertion loss and shorten the resonant cavity length, thereby limiting the influence of the uneven thermal lens effect on the cavity stability to the gain resonant cavity and lowering the threshold of the gain resonant cavity. On the other hand, an auxiliary loss resonant cavity is provided to further reduce the mode oscillation threshold by utilizing the principle of non-Hermitian coupling, thereby improving the quality of the output light beam.

[0006] In an optional embodiment, the first cavity includes a reflecting mirror and a first coupling-out mirror; wherein the reflecting mirror and the first coupling-out mirror form a resonance space.

[0007] In an optional embodiment, the reflector is coated with a dielectric film and a high-reflectivity reflective film; wherein the dielectric film has a high laser-induced damage threshold.

[0008] In an optional embodiment, the first cavity and the second cavity share the first coupling output mirror; the second cavity includes a second coupling output mirror; wherein the second coupling output mirror cooperates with the first coupling output mirror to form a resonant space.

[0009] In the above implementation, a coupling channel between the gain resonant cavity and the loss resonant cavity is established through a coupling output mirror to form an auxiliary loss resonant cavity.

[0010] In an optional embodiment, the first coupling output mirror and the second coupling output mirror are spectrometers, and the reflection and transmission ratio of the spectrometers is in the range of 6:4 to 9:1; the reflectivity of the first coupling output mirror is less than the reflectivity of the second coupling output mirror.

[0011] In an optional embodiment, the lens system includes a first lens, a second lens, and a pinhole stop arranged between the first lens and the second lens; wherein the first lens and the second lens are arranged between the first coupling output mirror and the second coupling output mirror, and the pinhole stop is arranged in a common focal plane of the first lens and the second lens.

[0012] In the above implementation, spatial filtering is performed on the central spectrum plane of the auxiliary loss resonant cavity, so that the low-order modes in the output beam of the main laser resonant cavity are selectively fed back, gain amplification is obtained in the main gain resonant cavity, other high-order modes are suppressed, and finally a high-quality beam is output.

[0013] In an optional embodiment, the aperture of the pinhole diaphragm is continuously adjustable in the range of 0.2 mm to 10 mm.

[0014] In the above implementation, the aperture of the pinhole diaphragm is in an adjustable state to meet the needs of lasers of more different sizes and improve the flexibility of the solid-state laser.

[0015] In an optional embodiment, the first lens includes any one of a biconvex lens, a plano-convex lens, and a convex lens with a short focal length; the second lens includes any one of a biconvex lens, a plano-convex lens, and a convex lens with a short focal length.

[0016] In an optional embodiment, the gain medium component includes a gain medium and a pump source; wherein the pump source is used to emit photons to pump electrons in the gain medium from a ground state energy level to an excited state energy level to achieve population inversion.

[0017] In an optional embodiment, the method further comprises: a polarization device disposed in the first cavity; wherein the polarization device is used to control the polarization state of the laser so that the emitted laser is linearly polarized light. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 A schematic diagram of the structure of a solid-state laser provided in an embodiment of the present application; Figure 2 A schematic structural diagram of another solid-state laser provided in an embodiment of the present application; Figure 3a A schematic diagram of the power and current of a solid-state laser obtained by measurement in an example provided in an embodiment of the present application; Figure 3b A schematic diagram of power and current obtained based on a simulation of a solid-state laser in an example provided in an embodiment of the present application; Figure 4 Schematic diagram of the spectrum of the resonant cavity structure under multiple examples.

[0020] Icons: 110-gain resonant cavity; 111-reflecting mirror; 112-first coupling output mirror; 113-gain medium component; 1131-gain medium; 1132-pump source; 1133-current source; 114-polarization device; 120-loss resonant cavity; 121-lens system; 1211-first lens; 1212-second lens; 122-second coupling output mirror; 123-pinhole aperture. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described below in conjunction with the accompanying drawings in the embodiments of the present application.

[0022] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. At the same time, in the description of this application, the terms "first", "second", etc. are only used to distinguish the description and should not be understood as indicating or implying relative importance.

[0023] In the description of this application, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive products are usually placed when in use. 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, be constructed and operated in a specific orientation, and therefore cannot be interpreted as a limitation of this application.

[0024] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0025] For lasers, lowering the threshold is one of the core goals of laser technology research and is of great significance to the performance optimization and application expansion of lasers. In short-cavity lasers, high pump currents will lead to increased mode competition, making it difficult to achieve stable single-mode output; in long-cavity lasers, long-distance diffraction loss and the thermal effect of large currents will increase cavity loss, making it difficult to excite the mode to output lasers. Traditional methods of lowering the threshold are mainly through the design of the cavity structure, such as using a flat concave cavity structure to reduce diffraction loss. However, most methods of reducing diffraction loss usually reduce the loss interval of the mode, resulting in multi-mode oscillation and reduced beam quality.

[0026] However, the current demand for lasers, that is, in most laser applications, requires lasers to have good directivity, that is, the output laser beam should have the smallest possible divergence. Although multi-transverse mode oscillating lasers have high output power, the characteristics of multiple π phase jumps in the high-order mode field distribution cause the far-field distribution of the output beam to split into multiple main lobes with a certain angle. This not only weakens the central intensity of the far-field distribution, but also increases the divergence angle of the laser beam, seriously restricting the application range of the laser. In order to compress the divergence of the laser beam, the usual method is to compress the laser oscillation mode, that is, by selecting the transverse mode, the fundamental mode oscillation and output of the laser are achieved, thereby obtaining good directivity. However, this implementation method greatly reduces the effective utilization of the active area of ​​the gain medium. Therefore, for practical applications in classical and quantum fields such as laser processing and laser communication, there is an urgent need to develop low-threshold single-mode lasers.

[0027] There are usually two solutions for transverse mode selection technology: the first is to change the structure and parameters of the resonant cavity to obtain a large mode loss spacing and improve the mode selection performance of the cavity itself. Taking the parallel plane cavity as an example, although increasing the cavity length increases the mode loss spacing, it also increases the loss of the target mode; the other is to insert additional mode selection elements (aperture diaphragm, "FP" standard, critical angle reflector, discharge tube or working medium) into the resonant cavity to suppress high-order mode oscillations and improve mode selection performance. This solution is at the expense of discarding high-order mode energy. Due to the compression of the oscillation mode volume, the single-mode output power is bound to be much smaller than the output power of multi-mode operation.

[0028] Based on the above research, the present application provides a solid-state laser, which reduces mode diffraction loss and increases effective coupling energy through an auxiliary loss resonant cavity 120, greatly reduces the threshold of the laser and improves the beam quality.

[0029] Figure 1 This is a schematic diagram of the structure of the solid-state laser provided in the embodiment of the present application. Figure 1 As shown, the solid-state laser includes a gain resonant cavity 110 and a loss resonant cavity 120 connected to the gain resonant cavity 110 .

[0030] The gain resonant cavity 110 may include a first cavity and a gain medium component 113 disposed in the first cavity.

[0031] The gain resonant cavity 110 can be used to reflect light back and forth within the gain resonant cavity 110 to extend the working length of the gain medium component 113, suppress spontaneous emission of photons, and increase the photon density within the cavity. The gain medium component 113 is used to provide optical gain.

[0032] The lossy resonant cavity 120 includes a second cavity and a lens system 121 disposed in the second cavity, for reducing diffraction loss of the auxiliary resonant cavity.

[0033] In this embodiment, Figure 2 As shown, the first cavity may include a reflecting mirror 111 and a first coupling-out mirror 112 .

[0034] The reflecting mirror 111 and the first coupling-out mirror 112 form a resonance space.

[0035] Optionally, the reflector 111 may be a high-reflectivity reflector 111. In one embodiment, the reflectivity of the high-reflectivity reflector 111 may be greater than 98%. The diameter of the high-reflectivity reflector 111 may be 25.4 mm or 50.8 mm. Depending on the actual design requirements, the high-reflectivity reflector 111 may also have other sizes.

[0036] Optionally, the reflector 111 is coated with a dielectric film and a high reflectivity reflective film.

[0037] Among them, the dielectric film has a high laser-induced damage threshold.

[0038] Exemplarily, the high-reflectivity reflective mirror may be a reflective mirror having a high-reflectivity reflective film. Exemplarily, the high-reflectivity reflective film may be a gold film, a silver film, or the like. The high-reflectivity reflective mirror may be a gold-coated plane reflective mirror or a silver-coated plane reflective mirror. In this embodiment, the reflectivity of the gold-coated plane reflective mirror may be greater than 98%, and the reflectivity of the silver-coated plane reflective mirror may be greater than 98%.

[0039] In this embodiment, the first cavity of the gain resonant cavity 110 and the second cavity of the auxiliary resonant cavity may share the first coupling output mirror 112 .

[0040] The second cavity includes a second coupling output mirror 122 ; wherein the second coupling output mirror 122 cooperates with the first coupling output mirror 112 to form a resonance space.

[0041] A coupling channel between the gain resonant cavity 110 and the loss resonant cavity 120 can be established through the first coupling output mirror 112 to form an auxiliary resonant cavity.

[0042] In this embodiment, the first coupling-out mirror 112 and the second coupling-out mirror 122 are beam splitters, and the reflection-transmission ratio of the beam splitters is in the range of 6:4 to 9:1.

[0043] For example, the first coupling-out mirror 112 may be a 6:4, 7:3, 8:2, 9:1, etc. reflection: transmission beam splitter. For example, the second coupling-out mirror 122 may be a 6:4, 7:3, 8:2, 9:1, etc. reflection: transmission beam splitter.

[0044] The reflectivity of the first coupling-out mirror 112 is lower than the reflectivity of the second coupling-out mirror 122 .

[0045] For example, when the reflectivity of the second coupling output mirror 122 is 90% and the reflectivity of the first coupling output mirror 112 is 70%; when the reflectivity of the second coupling output mirror 122 is 80% and the reflectivity of the first coupling output mirror 112 is 60%, a significant threshold reduction phenomenon can be observed.

[0046] Optionally, the diameters of the first and second coupling-out mirrors 112 and 122 are 25.4 mm or 50.8 mm. Of course, depending on the size of the solid-state laser actually designed, the sizes of the first and second coupling-out mirrors 112 and 122 may also be different from the values ​​in the above examples.

[0047] In this embodiment, Figure 2As shown, the lens system 121 includes a first lens 1211 , a second lens 1212 , and an aperture stop 123 disposed between the first lens 1211 and the second lens 1212 .

[0048] The first lens 1211 and the second lens 1212 are arranged between the first coupling output mirror 112 and the second coupling output mirror 122 , and the pinhole stop 123 is arranged at a common focal plane of the first lens 1211 and the second lens 1212 .

[0049] Among them, the first coupling output mirror 112 is set at the focus of the non-common focal plane of the first lens 1211, and the second coupling output mirror 122 can be set at the focus of the non-common focal plane of the second lens 1212 to ensure that the object and image of the first coupling output mirror 112 and the second coupling output mirror 122 are conjugated.

[0050] For example, the first lens 1211 and the second lens 1212 can form a confocal telescope system and be placed in the second cavity. The plane where the focal points of the first lens 1211 and the second lens 1212 are located is called the common focal plane. The pinhole stop 123 can be set at the common focal plane of the first lens 1211 and the second lens 1212 to suppress high-order modes.

[0051] To reduce loss, each optical element, including the first lens 1211, the second lens 1212, and the pinhole stop 123, may be coated with an anti-reflection film or a high-reflection film for lasers of a specified wavelength. For example, the specified wavelength may be 1064 nm.

[0052] Optionally, the aperture of the pinhole diaphragm 123 is continuously adjustable within a range of 0.2 mm to 10 mm. Optionally, the pinhole diaphragm 123 may be a structure of different shapes, such as a square diaphragm or a circular diaphragm.

[0053] Optionally, the first lens 1211 may include any one of a biconvex lens, a plano-convex lens, and a convex lens with a short focal length.

[0054] Optionally, the second lens 1212 includes any one of a biconvex lens, a plano-convex lens, and a convex lens with a short focal length.

[0055] In this embodiment, the focal lengths of the first lens 1211 and the second lens 1212 can be the same. For example, the focal lengths of the first lens 1211 and the second lens 1212 can both be 20 cm, or 30 cm, etc. Alternatively, the diameters of the first lens 1211 and the second lens 1212 can be 25.4 mm or 50.8 mm. Of course, depending on the size of the actual solid-state laser being designed, the sizes of the first lens 1211 and the second lens 1212 can also differ from those in the aforementioned examples.

[0056] In this embodiment, Figure 2 As shown, the gain medium component 113 includes a gain medium 1131 and a pump source 1132 .

[0057] The pump source 1132 is used to emit photons to pump electrons in the gain medium 1131 from the ground state energy level to the excited state energy level to achieve population inversion.

[0058] Optionally, the gain medium 1131 may be a Nd:YAG crystal rod, or Nd:Glass, Nd:YLF, Nd:YO4 or other Nd 3+ Doped gain medium 1131.

[0059] In one example, the concentration of the gain medium 1131 can be 0.6 at% to 1.2 at%, with a length of 30 to 100 mm, a diameter of 3 to 5 mm, and a cylindrical or square structure.

[0060] Nd:YAG is used as the gain medium 1131, which exhibits excellent thermal and mechanical properties and enables high-power operation. Nd:YO4, with its unique combination of high absorption cross-section, wide absorption bandwidth, and excellent thermal conductivity, enables efficient heat dissipation and reduces thermal effects. Nd:YLF offers a wider emission spectrum, providing improved tunability for ultrafast lasers. Nd:Glass has a smaller emission cross-section than other crystals, but its longer fluorescence lifetime allows for greater energy storage, enabling the generation of high-energy laser pulses.

[0061] Optionally, the pump source 1132 may be a high-power device such as a laser diode bar, a krypton lamp, a xenon lamp, or an 808 nm semiconductor laser.

[0062] Optionally, the solid-state laser may further include a current source 1133 connected to the pump source 1132. The current source 1133 may employ continuous-flow pumping, quasi-continuous-flow pumping, or pulsed pumping. Quasi-continuous-flow pumping and pulsed pumping can significantly reduce the thermal effects of the gain medium 1131, further improving beam quality.

[0063] Alternatively, as Figure 2 As shown, the solid laser may further include: a polarization device 114 disposed in the first cavity.

[0064] The polarization device 114 is used to control the polarization state of the laser so that the emitted laser light is linearly polarized light.

[0065] Optionally, the polarization device 114 may be a polarization beam splitter cube, a crystal polarization prism, etc., which can obtain linearly polarized light. The crystal polarization prism may be a Glan-Taylor crystal polarization prism.

[0066] The extinction ratio (Tp:Ts) of the polarization beam splitter cube is greater than 3000:1, and the extinction ratio (Tp:Ts) of the Glan-Taylor crystal polarizing prism is greater than 100,000:1. Different polarization devices 114 can be selected based on different actual needs.

[0067] The following describes the relative position and installation of the gain resonator 110 of the main body, using a combination of the aforementioned embodiments as an example: a high-reflectivity mirror 111 is placed at one end of the Nd:YAG crystal rod, a first output coupling mirror 112 is placed at the other end of the Nd:YAG crystal rod, a polarization beam splitter cube is placed between the Nd:YAG crystal rod and the first output coupling mirror 112, and the Nd:YAG crystal rod and the pump source 1132 are positioned at the same position. The pump source 1132 is connected to a current source 1133 via positive and negative wires.

[0068] The following describes the relative position and installation of the auxiliary loss resonator 120, using a combination of the aforementioned embodiments as an example: The auxiliary loss resonator 120 is composed of a first output coupling mirror 112 and a second output coupling mirror 122. When both the first lens 1211 and the second lens 1212 are biconvex lenses, the biconvex lenses form a confocal telescope system and are positioned within the second cavity formed by the loss resonator 120. The plane where the focal points of the biconvex lenses lie is called the common focal plane. An adjustable aperture diaphragm 123 is positioned at the common focal plane to suppress high-order modes. The first output coupling mirror 112 is positioned at the focal point of the non-common focal plane of the first lens 1211, and the second output coupling mirror 122 is positioned at the focal point of the non-common focal plane of the second lens 1212. This ensures that the object and image of the first output coupling mirror 112 and the second output coupling mirror 122 are conjugated, thus enabling the loss resonator 120 to form a degenerate cavity structure.

[0069] The high-reflectivity reflector 111 and the first coupling output mirror 112 form the main resonant cavity. By reflecting light back and forth within the cavity, the working length of the Nd:YAG crystal rod is extended, suppressing spontaneous emission of photons and increasing the photon density within the cavity. The Nd:YAG crystal rod has an energy level structure that causes population inversion, providing optical gain. The polarization beam splitter cube is used to control the polarization state of the laser, so that the output laser is linearly polarized light. The pump source 1132 serves as an energy source, emitting photons to pump electrons in the gain medium 1131 from the ground state energy level to a high energy level, thereby achieving population inversion. The current source 1133 generates current to power the pump source 1132. The positive and negative wires connecting the current source 1133 to the pump source 1132 form an electrical connection circuit, which enables the current source 1133 to power the pump source 1132. The first coupling output mirror 112 and the second coupling output mirror 122 form an auxiliary loss resonant cavity 120, and the confocal telescope system is used to reduce the diffraction loss of the auxiliary resonant cavity and perform mode control.

[0070] The embodiments of the present application utilize a non-Hermitian composite degenerate cavity structure, reducing costs by using only one gain crystal. This structure separates the main gain resonant cavity 110 from the auxiliary loss resonant cavity 120. This reduces the insertion loss of the gain resonant cavity 110 and effectively shortens the cavity length, thereby lowering the threshold of the gain resonant cavity 110. Furthermore, a coupling channel is established between the gain resonant cavity 110 and the loss resonant cavity 120 via a coupling output mirror, further lowering the mode's onset threshold using the principle of non-Hermitian coupling. Furthermore, the use of a non-Hermitian composite degenerate cavity structure allows for the construction of the gain resonant cavity 110 and the auxiliary loss resonant cavity 120 to be separated, while confining the impact of uneven thermal lensing on cavity stability to the gain resonant cavity 110, reducing the difficulty of cavity construction.

[0071] Furthermore, the embodiments of this application achieve a low-cost integrated design, requiring only a single gain crystal to implement the composite cavity function, significantly reducing material and assembly costs. The cavity functions are separated and optimized, with the main gain resonator 110 and the degenerate loss resonator 120 partially spatially decoupled, avoiding the insertion loss introduced by mode control components (such as etalons and apertures) in traditional designs. The main cavity length is also significantly shortened. This design approach achieves at least the following benefits: First, it increases the resonator's stable range, improving tolerance to misalignment; second, it reduces the pump threshold power, improving energy conversion efficiency. Thermal management advantages include: the thermal lensing effect is confined to the main cavity, and the auxiliary cavity is unaffected by thermal disturbances, simplifying the system's thermal compensation requirements. The dual-cavity collimation system is independently constructed, reducing assembly complexity and improving engineering feasibility. Through physical separation and functional synergy, this design achieves low loss, low threshold, and strong stability while maintaining mode control capabilities, providing a new approach for compact and cost-effective solid-state lasers.

[0072] In order to more clearly present the effects of the solid-state laser provided by the embodiments of the present application, the following is an introduction combining some principles: By performing spatial filtering on the central spectrum plane of the auxiliary loss resonant cavity 120, the low-order modes in the output light beam of the main gain resonant cavity 110 are selectively fed back, gain amplification is obtained in the gain resonant cavity 110, and an oscillation output is finally formed, while other modes are suppressed.

[0073] The following are instructions for reducing the laser threshold: The cavity dynamics process is established using the non-Hermitian coupled mode theory. Since the threshold reduction is actually a loss reduction phenomenon, from an overall perspective, if and It is reasonable to regard them as the linear superposition of the electric fields of all longitudinal modes of the gain resonant cavity 110 , and the gain here should also be regarded as the collective gain of the amplitude.

[0074] The amplitude term dynamics of the solid-state laser provided in the embodiments of the present application can be expressed as: ; in, represents the complex amplitude of the gain resonant cavity; represents the complex amplitude of the lossy resonant cavity; represents the gain coefficient of the gain resonant cavity; represents the loss coefficient of the gain resonant cavity; represents the transit time of the gain resonant cavity; represents the loss coefficient of the lossy resonant cavity; represents the transit time of the lossy resonant cavity; represents the coupling coefficient; represents the resonant frequency of the gain resonant cavity; represents the resonant frequency of the lossy resonant cavity; represents the pumping coefficient; represents the fluorescence lifetime.

[0075] use: ; in, represents the amplitude of the gain resonant cavity 110; represents the amplitude of the lossy resonant cavity 120.

[0076] The amplitude term dynamics of the above equation can be expressed as: .

[0077] Converted into strength equation: ;in, represents the light intensity of the gain resonant cavity 110; represents the light intensity of the loss resonant cavity 120.

[0078] make: .

[0079] but: .

[0080] Eliminating the AC change term, we get: .

[0081] When the system is in a stable state, it meets the following requirements: .

[0082] Therefore, we can get: .

[0083] Threshold conditions:

[0084] use: ; You can get: ; Threshold conditions: ; That is, we can get: .

[0085] Based on the above formulas, the relationship between the output light intensity and the pump coefficient can be solved. The gain resonant cavity of the main laser is called OC1+OC2, the auxiliary loss resonant cavity without the confocal telescope system is called OC2+OC3, the loss resonant cavity and the gain resonant cavity without the confocal telescope system are collectively called OC1+OC2+OC3, and the auxiliary resonant cavity with the confocal telescope system and the main laser resonant cavity are collectively called OC1+OC2+OC3+4f. Assume , Represents the removal of coupling output loss Excluding other losses, the output light intensity of the gain resonant cavity composed of OC1+OC2 is: ; The loss coefficient of the auxiliary loss resonant cavity after adding OC3: .

[0086] in, represents the diffraction loss of OC2+OC3, Represents the coupling loss between the cavity and OC1+OC2, Represents the output loss of the cavity.

[0087] Due to the overall loss reduction after OC3: ; It can be calculated that: ; The output light intensity can be expressed as: ; When added to the confocal telescope system, the diffraction loss of OC2+OC3 is almost zero.

[0088] At this time, the loss of the auxiliary resonant cavity is: .

[0089] Output light intensity: .

[0090] Summary: .

[0091] Here, in order to more clearly present the power current of the solid-state laser, the power current of the laser is measured experimentally, and the power current curve (PI curve) presented can be shown as follows: Figure 3a As shown in the figure, the comparison between OC1+OC2 and OC1+OC2+OC3 shows that the output loss and threshold are reduced after adding OC3. However, since the confocal telescope system is not included at this time, the diffraction loss of the auxiliary loss resonant cavity is too large, resulting in a decrease in output power under high current; the comparison between OC1+OC2+OC3 and OC1+OC2+OC3+4f shows that the diffraction loss is reduced after adding the confocal telescope system, and the system threshold is lowered.

[0092] based on Figure 3a It can be seen from the curve shown that the composite degenerate cavity structure can significantly reduce diffraction loss, lower the system threshold and increase the output power.

[0093] For theoretical results, in one example, , , , , Perform simulation, such as Figure 3b As shown in FIG, it shows a schematic diagram of the power current curve presented by the simulation results. Figure 3a and Figure 3b , we can see that the theoretical results are basically consistent with the experimental results. In the simulation results, the main reason for the fitting failure below the threshold is that part of the spontaneous emission is coupled to the stimulated emission.

[0094] like Figure 4As shown in the figure, it shows the spectra of the resonant cavity structures under multiple examples. Due to the spatial hole burning effect, the laser with the OC1+OC2 structure exhibits multi-longitudinal mode oscillation and a broad spectrum structure. For lasers with auxiliary cavities OC1+OC2+OC3 and OC1+OC2+OC3+4f structures, the spectra all show a certain red shift phenomenon, which is caused by the participation of the external cavity in the laser resonance process. At the same time, the spectra all show a certain broadening. This is because the composite degenerate cavity lowers the threshold of the cavity, thereby exciting the longitudinal modes below the threshold when there is only a gain resonant cavity. However, due to the mode selection effect of the external cavity, the oscillation of the longitudinal mode is suppressed, and the final spectrum is above the threshold and conforms to the result of the linear superposition of the cavity eigenmode.

[0095] The foregoing is merely an optional embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined or explained in subsequent figures.

[0096] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A solid-state laser, characterized in that: include: A gain resonant cavity and a loss resonant cavity connected to the gain resonant cavity; The gain resonant cavity comprises a first cavity and a gain medium component disposed in the first cavity, wherein the gain resonant cavity is used to extend the working length of the gain medium component by reflecting light back and forth in the cavity, thereby suppressing spontaneous emission of photons; wherein the gain medium component is used to provide optical gain; The loss resonant cavity includes a second cavity and a lens system arranged in the second cavity. The loss resonant cavity is used to reduce the diffraction loss of the auxiliary resonant cavity.

2. The solid-state laser according to claim 1, characterized in that The first cavity includes a reflecting mirror and a first coupling output mirror; wherein the reflecting mirror and the first coupling output mirror form a resonance space.

3. The solid-state laser according to claim 2, wherein The reflector is plated with a dielectric film and a high-reflectivity reflective film; wherein the dielectric film has a high laser-induced damage threshold.

4. The solid-state laser according to claim 2, characterized in that The first cavity and the second cavity share the first coupling output mirror; The second cavity includes a second coupling output mirror; wherein the second coupling output mirror cooperates with the first coupling output mirror to form a resonance space.

5. The solid-state laser according to claim 4, characterized in that The first coupling output mirror and the second coupling output mirror are beam splitters, and the reflection to transmission ratio of the beam splitters is in the range of 6:4 to 9:1; The reflectivity of the first coupling-out mirror is lower than the reflectivity of the second coupling-out mirror.

6. The solid-state laser according to claim 4, characterized in that The lens system includes a first lens, a second lens, and an aperture stop disposed between the first lens and the second lens; The first lens and the second lens are arranged between the first coupling output mirror and the second coupling output mirror, and the pinhole stop is arranged on a common focal plane of the first lens and the second lens.

7. The solid-state laser according to claim 6, wherein The aperture of the pinhole diaphragm is continuously adjustable in the range of 0.2 mm to 10 mm.

8. The solid-state laser according to claim 6, characterized in that The first lens includes any one of a biconvex lens, a plano-convex lens, and a short-focal-length convex lens; The second lens includes any one of a biconvex lens, a plano-convex lens, and a convex lens with a short focal length.

9. The solid-state laser according to claim 1, characterized in that The gain medium component includes a gain medium and a pump source; The pump source is used to emit photons to pump electrons in the gain medium from the ground state energy level to the excited state energy level to achieve population inversion.

10. The solid-state laser according to any one of claims 1 to 9, wherein Also includes: a polarization device disposed in the first cavity; The polarization device is used to control the polarization state of the laser so that the emitted laser is linearly polarized light.

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