All-solid-state continuous wave single-frequency laser

Abstract

The invention discloses an all-solid-state continuous wave single-frequency laser which comprises a symmetrical annular resonant cavity, and a first gain part and a second gain part are arranged in the symmetrical annular resonant cavity. The first gain part comprises at least one first gain crystal which is arranged in the symmetrical annular resonant cavity and has a natural birefringence characteristic; the second gain part comprises at least one second gain crystal which is arranged in the symmetrical annular resonant cavity and has a heat conduction coefficient greater than a threshold value; wherein the pump light power and wavelength of the symmetrically arranged first gain crystals are the same, and the pump light power and wavelength of the symmetrically arranged second gain crystals are the same. Different gain crystals are inserted into the symmetrical annular resonant cavity, on one hand, only one stable region exists in the resonant cavity through the second gain crystal; and on the other hand, the first gain crystal is used as a polarization selection element of the second gain crystal, and the first gain crystal can also be used as a mode selection element, so that stable single-frequency laser operation of the laser is realized.

Description

Technical Field

[0001] The present application relates to the technical field of lasers, and more particularly, to a all-solid-state continuous-wave single-frequency laser. Background Art

[0002] All-solid-state continuous-wave single-frequency lasers have been widely used in many fields such as quantum optics and quantum information, atomic physics, and high-precision measurement due to their advantages of good beam quality, high power stability, narrow linewidth, and low noise. Using an all-solid-state continuous-wave single-frequency laser as a basic light source, nonlinear frequency conversion technologies such as frequency doubling, sum frequency, difference frequency, optical parametric oscillation, and Raman can be used for wavelength extension and the preparation of non-classical optical fields. With the rapid development of science and technology, many fields urgently require increasing the output power of all-solid-state continuous-wave single-frequency lasers to meet application requirements. Especially in the field of laser interferometer gravitational wave detection (LIGO), increasing the output power of all-solid-state continuous-wave single-frequency lasers can effectively improve the sensitivity of the detection system.

[0003] Currently, increasing the output power of all-solid-state continuous-wave single-frequency lasers is mainly achieved through laser amplification technology. Although laser amplification technology is an effective method for obtaining high-power single-frequency laser output, limited by the thermal lens effect and low damage threshold of solid bulk laser crystals, to increase the output power of the amplification system, it is necessary to continuously increase the amplification stage, which will not only increase the complexity of the system, but also synchronously amplify the laser noise during the amplification of the output power. Therefore, people hope to achieve high-power continuous-wave single-frequency laser output through a single resonant cavity. However, to achieve high-power laser output, it is also necessary to insert multiple bulk laser crystals into a single resonant cavity. And only by artificially and rapidly increasing the pump light power injected into the resonant cavity (controlling the thermal lens focal length of the gain medium) can the laser successfully jump from the first stable region to the second stable region and operate stably.

[0004] In recent years, single-crystal fiber, as a combination of bulk crystal and traditional fiber, has become an increasingly popular amplifier gain medium due to its advantages such as high Brillouin scattering threshold, good thermal management characteristics, and pump light waveguide effect. However, since the laser emitted by YAG single-crystal fiber has no specific polarization direction, to achieve linearly polarized laser output, a polarization selection element needs to be inserted into the cavity. Summary of the Invention

[0005] The present application provides a all-solid-state continuous-wave single-frequency laser, in which a first gain crystal with natural birefringence characteristics and a second gain crystal with a thermal conductivity greater than a threshold are inserted into a symmetric ring resonator. On the one hand, the second gain crystal has good thermal management characteristics, making the thermal effect of the resonator relatively small and there is only one stable region. On the other hand, since the laser emitted by the first gain crystal is linearly polarized laser, it can be used as both a gain medium and a polarization-selecting element for the second gain crystal, and the first gain crystal can also be used as a mode-selecting element, enabling the second gain crystal to emit laser with the same mode as the first gain crystal, so that the laser can achieve stable single-frequency laser operation.

[0006] The present application provides a all-solid-state continuous-wave single-frequency laser, including a symmetric ring resonator, and a first gain section and a second gain section are arranged in the symmetric ring resonator;

[0007] The first gain section includes at least one first gain crystal with natural birefringence characteristics arranged in the symmetric ring resonator;

[0008] The second gain section includes at least one second gain crystal with a thermal conductivity greater than a threshold arranged in the symmetric ring resonator;

[0009] Wherein, all the first gain crystals and all the second gain crystals have independent pump sources, and the pump light powers and wavelengths of the symmetrically arranged first gain crystals are the same, and the pump light powers and wavelengths of the symmetrically arranged second gain crystals are the same.

[0010] Preferably, a first lens for mode matching is arranged between adjacent first gain crystals and between adjacent second gain crystals.

[0011] Preferably, a second lens for mode matching is arranged between an adjacent first gain crystal and a second gain crystal.

[0012] Preferably, a nonlinear crystal is arranged at the beam waist between the output mirror of the symmetric ring resonator and its adjacent first mirror.

[0013] Preferably, the first gain crystal is a bulk gain medium or a rod-shaped gain medium, and the second gain crystal is a plate-shaped gain medium, a thin-film gain medium or a single-crystal optical fiber.

[0014] Preferably, both the output mirror and the first mirror are plano-concave mirrors with an incident angle of 10 degrees.

[0015] Preferably, the symmetric ring resonator includes a symmetrically arranged second mirror and a third mirror, and both the second mirror and the third mirror are concave-convex mirrors with an incident angle of 10 degrees.

[0016] Preferably, the output end face of the first gain crystal has a wedge angle.

[0017] Preferably, a 90° quartz rotator is provided between adjacent second gain crystals, and a half-wave plate is provided between one of the first gain crystals and its adjacent second gain crystal.

[0018] Preferably, a prism adjacent to the position of the half-wave plate is further provided in the symmetric ring resonator.

[0019] Other features and advantages of the present application will become clear from the following detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings. Description of the Drawings

[0020] The drawings incorporated in and constituting a part of this specification illustrate embodiments of the present application and, together with the description, serve to explain the principles of the present application.

[0021] Figure 1 Schematic structural diagram of the first embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application;

[0022] Figure 2 Schematic structural diagram of the second embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application;

[0023] Figure 3 Schematic structural diagram of the third embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application;

[0024] Figure 4 For Figure 3 The case where the waist radius of each gain crystal and the stable region of the symmetric ring resonator in the shown embodiment change with the change of the injected pump power;

[0025] Figure 5 For Figure 3 The experimental results of the output power of the shown embodiment;

[0026] Figure 6 Schematic structural diagram of the fourth embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application;

[0027] Figure 7 Schematic structural diagram of the fifth embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application;

[0028] Figure 8 Schematic structural diagram of the sixth embodiment of the all-solid-state continuous-wave single-frequency laser provided by the present application. Detailed Embodiments

[0029] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present application.

[0030] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application or its application or use.

[0031] Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods, and devices should be regarded as part of the specification.

[0032] In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0033] The present application provides a all-solid-state continuous-wave single-frequency laser. A first gain crystal with natural birefringence characteristics and a second gain crystal with a thermal conductivity coefficient greater than a threshold are inserted into a symmetric ring resonator. On the one hand, the second gain crystal has a relatively large thermal conductivity coefficient and good thermal management characteristics, making the thermal effect of the resonator relatively small and having only one stable region. On the other hand, since the first gain crystal has natural birefringence characteristics, the laser it emits is linearly polarized laser. Therefore, it can serve as both a gain medium and a polarization-selective element for the second gain crystal, and the first gain crystal can also serve as a mode selection element, enabling the second gain crystal to emit laser with the same mode as the first gain crystal, thereby enabling the laser to achieve stable single-frequency laser operation.

[0034] The all-solid-state continuous-wave single-frequency laser provided by the present application includes a symmetric ring resonator, and a first gain section and a second gain section are provided in the symmetric ring resonator. A nonlinear crystal is provided at the beam waist between the output mirror of the symmetric ring resonator and the adjacent first mirror to ensure that the nonlinear loss introduced by it is sufficient to suppress the multimode oscillation and mode hopping phenomenon of the laser, and to achieve stable single-frequency operation of the laser. A unidirectional isolator is also provided in the symmetric ring resonator to effectively eliminate the spatial hole burning effect and force the laser to achieve stable unidirectional operation.

[0035] The first gain section includes at least one first gain crystal with natural birefringence characteristics disposed in a symmetric ring resonator. The second gain section includes at least one second gain crystal with a thermal conductivity greater than a threshold value (e.g., 10 W / m / K) disposed in the symmetric ring resonator. The gain crystals of different gain sections are different, and all the gain crystals in the same gain section are identical. Among them, all the first gain crystals and all the second gain crystals have independent pump sources, and the pump light powers and wavelengths of the symmetrically disposed first gain crystals are the same, and the pump light powers and wavelengths of the symmetrically disposed second gain crystals are the same.

[0036] As an embodiment, the first gain crystal is a bulk gain medium or a rod-shaped gain medium, and the second gain crystal is a plate-shaped gain medium, a thin-film gain medium, or a single-crystal optical fiber.

[0037] Preferably, a first lens for mode matching is provided between adjacent first gain crystals and between adjacent second gain crystals.

[0038] Preferably, a second lens for mode matching is provided between an adjacent first gain crystal and a second gain crystal.

[0039] Preferably, a 90° quartz rotator is provided between adjacent second gain crystals, and a half-wave plate is provided between one of the first gain crystals and its adjacent second gain crystal. On this basis, preferably, a prism adjacent to the position of the half-wave plate is further provided in the symmetric ring resonator.

[0040] The present application will be further described below by taking a symmetric ring resonator with an 8-shaped optical path as an example.

[0041] Embodiment 1

[0042] As Figure 1 shown in the embodiment, in the symmetric ring resonator, the output cavity mirror 12 is symmetric with the adjacent first cavity mirror 11 in position, the second cavity mirror 1 and the third cavity mirror 2 are symmetric in position, and the first cavity mirror 11, the output cavity mirror 12, the second cavity mirror 1, and the third cavity mirror 2 form an 8-shaped optical path. A unidirectional device 14 is provided between the second cavity mirror 1 and the output cavity mirror 12, and the unidirectional device 14 allows light to be transmitted from the second cavity mirror 1 to the output cavity mirror 12. A nonlinear crystal 13 is provided at the waist of the beam between the first cavity mirror 11 and the output cavity mirror 12.

[0043] On the optical path between the second cavity mirror 1 and the third cavity mirror 2, there is a first gain crystal L 1 and a second gain crystal L 3 , and a first pump source injects pump light into L 1 from the second cavity mirror 1, and a third pump source injects pump light into L 3 from the third cavity mirror 2.

[0044] As an embodiment, the first pump source and the third pump source are fiber-coupled laser diodes, and the pump lights P output by the first pump source and the third pump source 1 and P 3 have different wavelengths and / or powers.

[0045] As an embodiment, the resonant cavity adopts an end-pumping method. End-pumping is easier to achieve precise mode matching, and it is also easier to obtain high-beam-quality and high-power laser output.

[0046] As an embodiment, as Figure 1 shown, the second cavity mirror 1 and the third cavity mirror 2 are convex-concave mirrors with a 10-degree incidence angle. The pump incident end face of the second cavity mirror 1 is coated with a high-transmission film for the pump light P 1 and the other end face is coated with a high-transmission film for the pump light P 1 and a high-reflection film for the fundamental frequency light. The pump incident end face of the third cavity mirror 2 is coated with a high-transmission film for the pump light P 3 and the other end face is coated with a high-transmission film for the pump light P 3 and a high-reflection film for the fundamental frequency light. The first cavity mirror 11 and the output cavity mirror 12 are plano-concave mirrors with a 10-degree incidence angle. The plane of the first cavity mirror 11 is coated with a high-transmission film for the fundamental frequency light and the second harmonic light, and the concave surface is coated with a high-reflection film for the fundamental frequency light and a high-transmission film for the second harmonic light. The plane of the output cavity mirror 12 is coated with a high-transmission film for the fundamental frequency light and the second harmonic light, and the concave surface is coated with a high-transmission film for the second harmonic light and a transmission film with a preset transmittance for the fundamental frequency light.

[0047] Preferably, a plano-convex mirror f 1 and L 3 for realizing mode matching is provided between 1 , and the plano-convex mirror f 1 is coated with a high-reflection film for the fundamental frequency light.

[0048] As an embodiment, the nonlinear crystal 13 can be temperature phase matching or angle phase matching. The present application does not limit the material of the nonlinear crystal 13.

[0049] As an embodiment, the first gain crystal of the first gain part is a solid-state bulk gain crystal (such as Nd:YVO 4The second gain crystal of the second gain section is a single-crystal optical fiber (such as Nd:YAG crystal), while the first gain crystal of the first gain section is a bulk gain crystal. If the bulk gain crystal has natural birefringence and the emitted laser is linearly polarized laser, then the laser passing through the second gain crystal is linearly polarized light. Under the pumping action, the laser output from the second gain crystal is also linearly polarized light with the same polarization as the laser emitted by the first gain crystal. Therefore, the first gain crystal can serve as a polarization-selective element for the single-crystal optical fiber; and the first gain crystal can also serve as a mode-selection element to achieve mode matching between the bulk gain crystal and the single-crystal optical fiber. Specifically, both gain crystals can emit lasers of the same wavelength (such as 1064nm laser). The linewidth of the laser emitted by the bulk gain crystal is relatively narrow, which will cause the gain of the single-crystal optical fiber at the same frequency as that of the bulk gain crystal to be larger, and emit a frequency with the same mode as that of the bulk gain crystal. Therefore, the bulk gain crystal also has the function of mode selection. In addition, the single-crystal optical fiber propagates in the form of a waveguide, has high gain and good thermal management characteristics, can greatly reduce the thermal effect in the resonant cavity, so that there is only one stable region in the resonant cavity, ensuring the stable operation of the laser.

[0050] Preferably, the output end face of the first gain crystal has a wedge angle, which acts as a polarization beam splitter to facilitate maintaining the stability of the polarization state of the laser.

[0051] As an embodiment, the first gain crystal is coated with indium thin film and placed in a copper temperature control furnace by vacuum indium soldering, and temperature control is carried out by a thermoelectric cooler (TEC). The heat sink is a copper block with cooling circulating water flowing through it. As another embodiment, the first gain crystal can also be directly water-cooled.

[0052] As an embodiment, the second gain crystal is wrapped in a nickel layer, and the nickel layer is closely attached to a copper block with cooling circulating water flowing through it. As another embodiment, the second gain crystal can also be coated with indium thin film and placed in a copper temperature control furnace by vacuum indium soldering, and is closely attached to a copper block with cooling circulating water flowing through it.

[0053] Embodiment 2

[0054] As shown Figure 2 The difference between the embodiment shown and Embodiment 1 is that the first gain section includes two first gain crystals L 1 and L 2 , and the two are exactly the same crystals.

[0055] Specifically, L 1 and L 2 are symmetrically placed in a symmetric ring resonator, and the pumping optical power and wavelength of L 1 and L 2 are the same. The first pump source and the second pump source respectively emit light to L 1 and L2 Input pump, the first pump source and the second pump source are the same pump source. L 1 On the optical path between L 2 Plane cavity mirrors 3, 9, 10 and 4 for changing the optical path and incident at 45 degrees are symmetrically arranged on the optical path between them, and the second gain crystal L 3 Is arranged between cavity mirrors 9 and 10, such that L 1 And L 2 Are symmetric with respect to L 3 Symmetric. The third pump source is incident from cavity mirror 9, and the pump incident end face of cavity mirror 9 is coated with a high-transmission film for pump light P 3 Another end face is coated with a high-transmission film for pump light P 3 High-transmission film and a high-reflection film for fundamental frequency light.

[0056] Preferably, between L 1 And L 3 A plano-convex mirror f for mode matching is provided 1 , L 2 And between L 3 A plano-convex mirror f for mode matching is provided 2 , The plano-convex mirror f 1 , f 2 Is coated with a high-reflection film for fundamental frequency light.

[0057] Example 3

[0058] The difference between the example shown in Example 3 and Example 2 is that the second gain part includes two second gain crystals L 3 And L 4 , Both are exactly the same crystals, and are both arranged between cavity mirrors 9 and 10, such that they are symmetrically arranged in a symmetric ring resonator, and L 3 And L 1 The optical path between them and L 4 And L 2 The optical path between them is symmetric. Among them, L 3 And L 4 The pump light power and wavelength are the same. The fourth pump source is incident from cavity mirror 10, and the pump incident end face of cavity mirror 10 is coated with a high-transmission film for pump light P 4 Another end face is coated with a high-transmission film for pump light P 4 High-transmission film and a high-reflection film for fundamental frequency light. The third pump source and the fourth pump source are the same pump source.

[0059] As Figure 3 Shown, on the optical path between cavity mirrors 3 and 9, plane cavity mirrors 5 and 7 for changing the optical path and incident at 45 degrees are provided, and on the optical path between cavity mirrors 4 and 10, plane cavity mirrors 6 and 8 for changing the optical path and incident at 45 degrees are provided. The reflecting surfaces of cavity mirrors 5, 7, 6 and 8 are coated with a high-reflection film for fundamental frequency light. The plano-convex mirror f 1 And f2 They are respectively arranged between endoscopes 7 and 9 and between endoscopes 8 and 10.

[0060] Preferably, L 3 Between L and L 4 There is at least one plano-convex mirror for realizing mode matching. Figure 3 It is shown in [X] that there are two plano-convex mirrors f between the two. 3 And f 4 The plano-convex mirror f 3 、f 4 Is coated with a high-reflection film for fundamental frequency light.

[0061] The second gain crystal has a depolarization effect caused by thermo-optic birefringence. Based on this consideration, preferably, between the plano-convex mirrors f 3 And f 4 There is a 90° quartz rotator 15. The 90° quartz rotator 15 is coated with a high-reflection film for fundamental frequency light, and between L 2 And L 4 There is a half-wave plate. The laser radiated by the first gain crystal is horizontally polarized light. After using a 90° rotator between the two second gain crystals, thermo-optic birefringence mutual compensation can be achieved. After the 90° quartz rotator, the polarization direction in the cavity rotates by 90°, changing from horizontal polarization to vertical polarization. The half-wave plate can rotate the polarization direction by 90 degrees, that is, from vertical polarization to horizontal polarization, so that the polarization direction in the cavity after the half-wave plate returns to the original polarization direction, ensuring the consistency of the polarization characteristics in the resonant cavity.

[0062] On the above basis, a prism adjacent to the position of the half-wave plate is also provided in the symmetric ring resonator. The half-wave plate and the prism form a combination 16. The prism can lead the depolarized laser out of the cavity, and on the other hand, it can ensure that the polarization direction of the light in the cavity is horizontally polarized light.

[0063] Figure 4 For Figure 3 In the embodiment shown, when the pump light P 3 And P 4 Injected at L and L are 90W, 120W, and 180W respectively, the beam waist radii at L 3 And P 4 And the stable region of the symmetric ring resonator change with the change of the power of the injected pump light P 1 And P 2 And L 3 And P 4 The situation shown in the figure, the pump power in the figure is the conversion result based on the thermal lens formula. Among them, the injected pump powers of L 1 And P 2 Change synchronously, and the injected pump powers of L 1 And P 2 Change synchronously, and the injected pump powers of L 3 And P 4The injection pump power changes synchronously. Due to the symmetric characteristics of the ring resonator, the beam waists at L 1 and L 2 are equal, and the beam waists at L 3 and L 4 are equal.

[0064] It can be seen from Figure 4 that the resonator has only one stable region, indicating that the single-crystal fiber has good thermal management characteristics, which is beneficial to achieving high-power laser output. Figure 4 (a) shows the variation of the beam waist radii at L 1 and L 2 with the change of P 1 -P 4 . It can be seen from the curves (i), (ii), and (iii) in Figure 4 (a) that when the pump powers P 3 and P 4 injected at L 3 and L 4 are 90W, 120W, and 180W respectively, the stable regions of the resonator adapt from 123.5W to 91W, 88W, and 80.5W respectively. When the pump powers P 1 and P 2 injected at L 1 and L 2 are 110W, the optimal beam waist radii at L 1 and L 2 are 480μm (P 3 =P 4 =90W), 460μm (P 3 =P 4 =120W), and 420μm (P 3 =P 4 =180W) respectively. At the same time, it can be seen from Figure 4 (b) that when the pump powers P 1 and P 2 injected at L 1 and L 2 are in the range of 110W to 120W, with the change of the injected pump powers P 3 and P 4 , the beam waist radii at L 3 and L 4 do not change significantly. It can be seen from the calculation results that compared with L 1 and L 2 , the thermal lens effect of L 3 and L 4 is relatively small. It can be seen from Figure 4 that when the pump P 1 and P2 is 110W, P 3 and P 4 is 120W, L 1 and L 2 at the best waist radius is about 460μm, L 3 and L 4 at the best waist radius is about 90μm.

[0065] In order to obtain high-power laser output, during the experiment, based on Figure 4 the calculation results, the total cavity length of the resonator and the distance between each component in the resonator were repeatedly optimized. When the designed resonator reached the best conditions, the relationship between the output power of the laser and the depolarization power reflected by the prism in the cavity and the total injected pump power was experimentally measured, and the results are as Figure 5 shown. It can be seen from the figure that when the total pump power of the pump light P 1 -P 4 is 477.3W (P 1 =113.7W, P 2 =113.7W, P 3 =123W, P 4 =126.9W), a stable single-frequency 1064nm laser with a maximum output power of 120W was obtained. In this case, from Figure 5 the curve (ii) in it can be seen that due to imperfect compensation, the output power of the depolarized laser is 17.9W. Figure 5 The curve (iii) in it is the sum of the output power and the depolarization power of the resonator.

[0066] It can be seen from the above that the resonator of the present application combines the advantages of two gain media, so there is only one stable region in the cavity, and there is no need to artificially and rapidly increase the pump light power injected into the resonator to change the stable region to achieve stable single-frequency operation.

[0067] Example 4

[0068] Figure 6 In the embodiment shown, the number of gain crystals in the first gain part and the second gain part is the same as that in Figure 3 the embodiment of Figure 3 The difference from the embodiment shown is that the symmetric ring resonator has fewer plane mirrors, only including cavity mirrors 3, 9, 10 and 4, L 3 is arranged between cavity mirrors 3 and 9, L 4 is arranged between cavity mirrors 4 and 10, the third pump source and the fourth pump source inject pump light from cavity mirrors 9 and 10 respectively, and the third pump source and the fourth pump source are the same pump source. L 3 and L 4 are symmetrically arranged, L 3and L 4 The pump light power and wavelength are the same. Plano-convex mirror f 3 , f 4 is set between cavity mirrors 9 and 10. L 1 and L 3 and between L 2 and L 4 no plano-convex mirror f 1 , f 2 .

[0069] Example 5

[0070] Figure 7 The shown example is different from Figure 6 in that plane cavity mirrors 5 and 7 with 45-degree incidence for changing the optical path are added between cavity mirrors 3 and 9, plane cavity mirrors 6 and 8 with 45-degree incidence for changing the optical path are added between cavity mirrors 4 and 10, plane cavity mirrors 19, 17, 18 and 20 with 45-degree incidence for changing the optical path are added between cavity mirrors 9 and 10, and the pump incident end face of cavity mirror 17 is coated with a high-transmission film for pump light P 5 and the other end face is coated with a high-transmission film for pump light P 5 and a high-reflection film for fundamental frequency light. L 3 is set between cavity mirrors 7 and 9, L 4 is set between cavity mirrors 8 and 10, a third gain crystal L 5 is provided between cavity mirrors 17 and 18, such that the optical path between L 1 and L 5 is symmetric with respect to the optical path between L 2 and L 5 with respect to L 5 , and the fifth pump source inputs pump light P 5 to the third gain crystal L 5 . A plano-convex mirror f 1 is provided between cavity mirrors 3 and 5, a plano-convex mirror f 2 is provided between cavity mirrors 4 and 6, a plano-convex mirror f 3 is provided between cavity mirrors 19 and 17, and a plano-convex mirror f 4 is provided between cavity mirrors 18 and 20.

[0071] As an example, the third gain crystal L 5 is the first gain crystal, and the fifth pump source is the same as the first pump source.

[0072] As another example, the third gain crystal L 5 is the second gain crystal, and the fifth pump source is the same as the third pump source.

[0073] Example 6

[0074] Figure 8The difference between the illustrated embodiment and the embodiment of Figure 7 is that a third gain crystal L is provided between the endoscopes 17 and 18 5 and a fourth gain crystal L 6 . The two are the same crystal and are symmetrically arranged in a symmetric ring resonator. L 5 and L 6 have the same pump light power and wavelength. The sixth pump source inputs pump light P 6 to the fourth gain crystal L 6 through the endoscope 18. The fifth pump source and the sixth pump source are the same pump source.

[0075] L 5 and L 6 are provided with plano-convex lenses f 5 and f 6 for mode matching. The plano-convex lenses f 5 and f 6 are coated with high reflectivity films for fundamental frequency light.

[0076] It should be noted that this application does not limit the number of gain crystals in each gain section, the number of plano-convex lenses for mode matching, and the number of endoscopes for changing the optical path. The number of 90° rotators and waveplate prism combinations is determined according to needs, as long as the characteristics of the ring resonator are satisfied and stable single-frequency laser operation is achieved based on the above technical principles.

[0077] The all-solid-state continuous-wave single-frequency laser provided by this application combines the advantages of two or more gain media to achieve stable single-frequency laser operation of the laser.

[0078] Although some specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of this application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. An all-solid-state continuous wave single-frequency laser, characterized in that: It comprises a symmetrical annular resonant cavity, wherein a first gain part and a second gain part are arranged in the symmetrical annular resonant cavity; The first gain section includes at least one first gain crystal having natural birefringence characteristics disposed in the symmetrical ring resonator; The second gain section includes at least one second gain crystal with a thermal conductivity greater than a threshold value disposed in the symmetrical ring resonator; All first gain crystals and all second gain crystals have independent pump sources, the pump light power and wavelength of the symmetrically arranged first gain crystals are the same, and the pump light power and wavelength of the symmetrically arranged second gain crystals are the same.

2. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: A first lens for mode matching is provided between adjacent first gain crystals and between adjacent second gain crystals.

3. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: A second lens for mode matching is arranged between the first gain crystal and the second gain crystal which are adjacent to each other.

4. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: A nonlinear crystal is arranged at the beam waist between the output cavity mirror of the symmetrical ring resonator and the adjacent first cavity mirror.

5. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: The first gain crystal is a block gain medium or a rod gain medium, and the second gain crystal is a slab gain medium, a thin-sheet gain medium or a single crystal optical fiber.

6. The all-solid-state continuous wave single-frequency laser according to claim 5, characterized in that: The output cavity mirror and the first cavity mirror are both plano-concave mirrors with an incidence of 10 degrees.

7. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: The symmetrical ring resonant cavity comprises a second cavity mirror and a third cavity mirror which are symmetrically arranged, and both the second cavity mirror and the third cavity mirror are concave-convex mirrors with an incidence of 10 degrees.

8. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: The first gain crystal has a wedge angle on its output end face.

9. The all-solid-state continuous wave single-frequency laser according to claim 1, characterized in that: A 90° quartz rotator is arranged between adjacent second gain crystals, and a half-wave plate is arranged between one of the first gain crystals and the adjacent second gain crystal.

10. The all-solid-state continuous wave single-frequency laser according to claim 9, characterized in that: A prism adjacent to the half-wave plate is also provided in the symmetrical annular resonant cavity.

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