A ring-shaped Q-switched multi-wavelength solid-state laser with wavelength decoupling cavity mirror structure

Abstract

This invention relates to a ring-type Q-switched multi-wavelength solid-state laser with a wavelength-decoupled cavity mirror structure, comprising a pump unit, a ring resonant cavity, a laser crystal, an acousto-optic Q-switcher, and a frequency-doubling crystal. The pump unit emits pump light to the laser crystal to excite it to generate fundamental frequency light. The ring resonant cavity includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror arranged sequentially along the light propagation direction. The laser crystal is positioned in the optical path between the first and second cavity mirrors. The acousto-optic Q-switcher and the frequency-doubling crystal are arranged sequentially in the optical path between the third and fourth cavity mirrors. The third cavity mirror is a high-reflection mirror for the fundamental frequency light and a low-reflection mirror for the frequency-doubling light. The fourth cavity mirror is a high-reflection lens for the frequency-doubling light, partially reflecting the fundamental frequency light. This invention can guide the frequency-doubling light circulating in the ring resonant cavity to the outside of the cavity, achieving wavelength decoupling, maintaining efficient Q-switched oscillation of the fundamental frequency light, and reducing the loss of the fundamental frequency light.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure. Background Technology

[0002] Multiwavelength solid-state lasers are widely used in nonlinear optics, precision machining, and optical inspection. Existing multiwavelength lasers mostly use linear resonant cavities or dichroic devices at the cavity ends to achieve different wavelength outputs. Under Q-switching and intracavity frequency doubling conditions, the frequency-doubled light is prone to multiple reflections within the cavity, resulting in increased intracavity loss and output instability.

[0003] In existing multi-wavelength solid-state lasers, under Q-switching and intracavity frequency doubling conditions, the frequency-doubled light is prone to multiple reflections within the cavity, leading to increased loss and unstable output. Both linear cavities and traditional ring cavities lack structural-level decoupling designs for reflectivity and propagation paths at different wavelengths, causing mutual interference between the fundamental and frequency-doubled light, reducing efficiency, and making it difficult to achieve stable, low-loss multi-wavelength output. These problems urgently need to be addressed. Summary of the Invention

[0004] This invention discloses a ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure, aiming to solve the technical problems existing in the prior art.

[0005] The present invention adopts the following technical solution: This invention provides a ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure, comprising a pump unit, a ring resonant cavity, a laser crystal, an acousto-optic Q-switcher, and a frequency-doubling crystal. The pump unit emits pump light to the laser crystal to excite the laser crystal to generate fundamental frequency light. The ring resonant cavity includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror arranged sequentially along the light propagation direction. The laser crystal is disposed in the optical path between the first cavity mirror and the second cavity mirror. The acousto-optic Q-switcher and the frequency-doubling crystal are disposed sequentially in the optical path between the third cavity mirror and the fourth cavity mirror. The third cavity mirror is a high-reflection mirror for the fundamental frequency light and a low-reflection mirror for the frequency-doubling light. The fourth cavity mirror is a high-reflection lens for the frequency-doubling light that partially reflects the fundamental frequency light.

[0006] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure of the present invention, the installation angle of the fourth cavity mirror is b, and 1 / 2arctan ≤ b ≤ Among them, 2w 2ω ≤Δ≤3w 2ω w 2ω The frequency-doubled light at the frequency-doubled crystal is 1 / e 2 The light spot radius, S4 is the distance from the frequency doubling crystal to the fourth cavity mirror. The maximum allowable mounting angle for the fourth cavity mirror in its working state; and / or, the mounting angle of the third cavity mirror is α, where 1 / 2arctan-b ≤ a ≤ Where S3 is the distance from the third cavity mirror to the frequency doubling crystal. This is the maximum allowable installation tilt angle for the third cavity mirror in its working state.

[0007] In the ring-shaped Q-switched multi-wavelength solid-state laser with wavelength decoupled cavity mirror structure of the present invention, the fundamental frequency reflectivity of the third cavity mirror is ≥99%, and the frequency-doubled light transmittance is ≥95%; and / or, the fundamental frequency reflectivity of the fourth cavity mirror is 90%-98%, and the frequency-doubled light transmittance is 98%-99.9%.

[0008] The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure of the present invention further includes a Faraday rotator, a quarter-wave plate, and a polarization beam splitter; the Faraday rotator, the quarter-wave plate, and the polarization beam splitter are sequentially arranged in the optical path between the acousto-optic Q-switcher and the frequency doubling crystal; the Faraday rotator is used to rotate the polarization direction by 45°; the polarization direction of the polarization beam splitter is the same as that of the fundamental frequency light.

[0009] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure of the present invention, the pump light output from the pump unit is transmitted through the first cavity mirror into the laser crystal.

[0010] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure of the present invention, the pump unit includes a pump source, a spot shaping unit, and a focusing coupling unit arranged sequentially; the pump source is used to generate pump light; the spot shaping unit is used to modulate the spatial energy distribution of the pump light to output a near-flat-top pump light; the focusing coupling unit is used to focus the pump light homogenized by the spot shaping unit with low aberration and couple it to the effective pump region of the laser crystal.

[0011] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure of the present invention, the spot shaping unit includes a collimation unit, a spot shaping component, and a focusing coupling unit arranged sequentially along the light propagation direction; the spot shaping component includes a plurality of microlens homogenizers arranged at intervals along the light propagation direction, used to divide the incident beam collimated by the collimation unit into a plurality of sub-beams, and to make the plurality of sub-beams form a spot with uniform intensity distribution after passing through the focusing coupling unit.

[0012] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure of the present invention, the focusing coupling unit is an aspherical focusing lens.

[0013] The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure of the present invention also includes a Brewster plate; the Brewster plate is disposed in the optical path between the frequency doubling crystal and the fourth cavity mirror.

[0014] In the ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure of the present invention, a non-polarizing beam splitter, a dual-wavelength λ / 2 waveplate, a frequency combining crystal, and a dichroic mirror are sequentially arranged on the transmission optical path of the fourth cavity mirror; the non-polarizing beam splitter is used to split the input light into at least two paths, one of which passes through the dual-wavelength λ / 2 waveplate, the frequency combining crystal, and the dichroic mirror; the dual-wavelength λ / 2 waveplate is used to rotate and align the linear polarization directions of the fundamental frequency light and the frequency-doubled light in the input light, so that their polarization directions are precisely aligned with the o-axis and e-axis of the frequency combining crystal; the dichroic mirror is used to separate and export the third wavelength light in the output light of the frequency combining crystal.

[0015] The technical solution adopted in this invention can achieve the following beneficial effects: This invention provides a ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure. It utilizes a ring resonant cavity formed by a first, second, third, and fourth cavity mirror to achieve intracavity oscillation of the fundamental frequency light. The third cavity mirror is configured as a high-reflection mirror for the fundamental frequency light and a low-reflection mirror for the frequency-doubled light, suppressing residual return during frequency doubling. The fourth cavity mirror is configured as a high-reflection lens for the frequency-doubled light, partially reflecting the fundamental frequency light, thus achieving coupling between the fundamental frequency output and the main output of the frequency-doubled light. This guides the frequency-doubled light circulating within the ring resonant cavity to the outside, achieving wavelength decoupling. This maintains efficient Q-switched oscillation of the fundamental frequency light, reduces its loss, and ensures stable intracavity modes for high-peak power pulses under multi-wavelength coexistence conditions. Furthermore, it avoids intracavity thermal effects, mode perturbations, and energy fluctuations caused by the repeated back-and-forth movement of the frequency-doubled light within the cavity, improving frequency doubling efficiency and achieving stable dual-wavelength output. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of a ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to the present invention; Figure 2 This is a schematic diagram of a ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to the present invention; Figure 3 This is a schematic diagram of the light spot shaping unit of the present invention.

[0017] Explanation of reference numerals in the attached figures: 1. Pump unit; 11. Pump source; 12. Beam shaping unit; 121. Collimation unit; 122. Beam shaping assembly; 1221. First microlens array; 1222. Second microlens array; 123. Focusing coupling unit; 13. Focusing coupling unit; 2. Ring resonator; 21. First cavity mirror; 22. Second cavity mirror; 23. Third cavity mirror; 24. Fourth cavity mirror; 3. Laser crystal; 4. Acousto-optic Q-switcher; 5. Frequency doubling crystal; 6. Faraday rotator; 7. 1 / 4 waveplate; 8. Polarization beam splitter; 9. Brewster plate; 101. Unpolarization beam splitter; 102. Dual-wavelength λ / 2 waveplate; 103. Frequency combining crystal; 104. Dichroic mirror. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0020] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] To address the problems existing in the prior art, this application provides a ring Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure.

[0022] like Figure 1As shown, a ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure includes a pump unit 1, a ring resonant cavity 2, a laser crystal 3, an acousto-optic Q-switcher 4, and a frequency-doubling crystal 5. The pump unit 1 is used to emit pump light to the laser crystal 3 to excite the laser crystal 3 to generate fundamental frequency light. The ring resonant cavity 2 includes a first cavity mirror 21, a second cavity mirror 22, a third cavity mirror 23, and a fourth cavity mirror 24 arranged sequentially along the light propagation direction. The laser crystal 3 is arranged in the optical path between the first cavity mirror 21 and the second cavity mirror 22. The acousto-optic Q-switcher 4 and the frequency-doubling crystal 5 are arranged sequentially in the optical path between the third cavity mirror 23 and the fourth cavity mirror 24. The third cavity mirror 23 is a high-reflection mirror for the fundamental frequency light and a low-reflection mirror for the frequency-doubling light. The fourth cavity mirror 24 is a high-reflection lens for the frequency-doubling light that partially reflects the fundamental frequency light.

[0023] This invention discloses a ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure. It utilizes a ring resonant cavity 2 formed by a first cavity mirror 21, a second cavity mirror 22, a third cavity mirror 23, and a fourth cavity mirror 24 to achieve intracavity oscillation of the fundamental frequency light. The third cavity mirror 23 is defined as a high-reflection mirror for the fundamental frequency light and a low-reflection mirror for the frequency-doubled light, suppressing residual return during frequency doubling. The fourth cavity mirror 24 is defined as a high-reflection lens for the frequency-doubled light, partially reflecting the fundamental frequency light, thus achieving coupling between the fundamental frequency output and the main output of the frequency-doubled light. This guides the frequency-doubled light circulating in the ring resonant cavity 2 to the outside of the cavity, achieving wavelength decoupling. This maintains efficient Q-switched oscillation of the fundamental frequency light, reduces its loss, and ensures stable intracavity modes for high-peak power pulses under multi-wavelength coexistence conditions. It also avoids intracavity thermal effects, mode disturbances, and energy fluctuations caused by the frequency-doubled light traveling back and forth within the cavity, improving the 5th-harmonic efficiency of the frequency-doubled crystal and achieving stable dual-wavelength output. This solves the problem that existing structures struggle to simultaneously achieve multi-wavelength stability and efficient transmission.

[0024] In some preferred embodiments, the mounting angle of the fourth cavity mirror 24 is b, which is the angle between the normal of the effective reflecting surface of the fourth cavity mirror 24 and the optical axis of the fundamental frequency light incident on the fourth cavity mirror 24; when b is 0, the effective reflecting surface of the fourth cavity mirror 24 is perpendicular to the optical axis of the incident fundamental frequency light, and 1 / 2arctanΔ / S4≤b≤ Among them, 2w 2ω ≤Δ≤3w 2ω Δ represents the minimum permissible lateral separation between the center of the residual frequency-doubled return spot on the corresponding light-transmitting end face of the frequency-doubled crystal and the principal optical axis of the fundamental frequency light, w 2ω The frequency-doubled light at point 5 of the frequency-doubled crystal is 1 / e 2 The light spot radius, S4, is the distance from the frequency doubling crystal 5 to the fourth cavity mirror 24, that is, the optical path distance between the light-transmitting end face of the frequency doubling crystal 5 near the fourth cavity mirror 24 and the effective reflecting surface of the fourth cavity mirror 24. This is the maximum allowable installation tilt angle for the fourth cavity mirror 24 in its working state. Based on the above angle coordination design, the frequency-doubled light forms a stable spatial angle with the fundamental frequency light after generation, which significantly reduces the spatial overlap between the residual frequency-doubled return light and the original main action area (that is, the spatial overlap area where the fundamental frequency light and the frequency-doubled light undergo effective frequency conversion), thereby suppressing its participation in effective frequency conversion again and its disturbance to the fundamental frequency cavity mode.

[0025] And / or, the mounting angle of the third cavity mirror 23 is α, which is the angle between the normal of the effective reflecting surface of the third cavity mirror 23 and the optical axis of the fundamental frequency light incident on the fourth cavity mirror 24, 1 / 2arctanΔ / S3-b≤a≤ Where S3 is the distance from the third cavity mirror 23 to the frequency doubling crystal 5, that is, S3 is the optical path distance between the effective reflecting surface of the third cavity mirror 23 and the light-transmitting end face of the frequency doubling crystal 5 near the third cavity mirror 23. This is the maximum allowable installation tilt angle for the third cavity mirror 23 in its working state. Within the same adjustment plane, the effective reflecting surface normals of the third cavity mirror 23 and the fourth cavity mirror 24 are tilted in opposite directions relative to their respective incident fundamental frequency light axes, causing the frequency-doubled residual light reflected by them to produce a lateral displacement relative to the fundamental frequency optical path, thereby reducing the spatial overlap between the frequency-doubled return light and the fundamental frequency cavity optical path.

[0026] Preferably, and The angle is 1° to 3°; based on this, the spatial decoupling effect of frequency doubling light and the stability of the ring resonator are taken into account.

[0027] In some preferred embodiments, the fundamental frequency reflectivity of the third cavity mirror 23 is ≥99%, and the frequency-doubled light transmittance is ≥95%. When the fundamental frequency reflectivity is too low, it will lead to increased round-trip loss within the cavity, raising the oscillation threshold and reducing the peak power of Q-switching. When the frequency-doubled light reflectivity is too high, the frequency-doubled light will undergo multiple reflections within the cavity, introducing additional losses and perturbing the fundamental frequency mode. When the frequency-doubled light reflectivity is too low but not designed in conjunction with the angle structure, it may still partially overlap with the fundamental frequency path, failing to achieve true spatial decoupling. And / or, the fundamental frequency reflectivity of the fourth cavity mirror 24 is 90%-98%, and the frequency-doubled light transmittance is 98%-99.9%. If the fundamental frequency reflectivity is too high, the output power decreases; if the fundamental frequency reflectivity is too low, the cavity oscillation conditions are difficult to meet. If the frequency-doubled light transmittance is too low, the frequency-doubled light is reflected back into the cavity, forming an invalid round trip, increasing additional losses within the cavity and perturbing the stability of the fundamental frequency oscillation.

[0028] Preferably, the mounting angle of the fourth laparoscope 24 is b, and 1 / 2arctanΔ / S4≤b≤ Among them, 2w 2ω ≤Δ≤3w 2ω w 2ω The frequency-doubled light at point 5 of the frequency-doubled crystal is 1 / e2 The light spot radius, S4 is the distance from the frequency doubling crystal 5 to the fourth cavity mirror 24. The maximum allowable installation tilt angle for the fourth cavity mirror 24 in working condition; the installation angle for the third cavity mirror 23 is α, where 1 / 2arctanΔ / S3-b≤a≤ Where S3 is the distance from the third cavity mirror 23 to the frequency doubling crystal 5. This is the maximum allowable installation tilt angle for the third cavity mirror 23 in its working state; based on this, it is possible to reduce the problems of introducing astigmatism, polarization loss, or insufficient suppression of frequency doubling residual return, further reduce the overlap between reflected frequency doubling light and fundamental light, and improve the spatial decoupling effect.

[0029] In some preferred embodiments, a Faraday rotator 6, a quarter-wave plate 7, and a polarization beam splitter 8 are also included. The Faraday rotator 6, quarter-wave plate 7, and polarization beam splitter 8 are sequentially arranged in the optical path between the acousto-optic Q-switcher 4 and the frequency doubling crystal 5. The Faraday rotator 6 is used to rotate the polarization direction by 45°. The polarization direction of the polarization beam splitter 8 is the same as that of the fundamental frequency light. Based on this, the reverse light is physically eliminated, upgrading the unidirectional criterion from polarization mismatch to polarization selection and path separation, allowing only the fundamental frequency laser to propagate in a single direction, effectively suppressing reverse oscillations and avoiding standing wave effects; and maintaining reliable isolation even under thermal drift of the Faraday rotator 6 or high-power Q-switching conditions.

[0030] The specific working process is as follows: The linearly polarized fundamental frequency light remains linearly polarized after passing through the Faraday rotator 6, but its polarization direction is rotated by 45°. It is then converted to circular or elliptical polarization by the λ / 4 waveplate 7 and incident on the polarization beam splitter 8 in a combined polarization state. The polarization beam splitter 8 only transmits the linearly polarized component aligned with its transmission axis, thus enabling low-loss transmission of the forward-propagating fundamental frequency light. When there is back-propagating light, after the back-propagating light first reaches the polarization beam splitter 8, it can still enter the λ / 4 waveplate 7 and the Faraday rotator 6 along the original optical path. Due to the reciprocity of the λ / 4 waveplate 7 and the non-reciprocal rotation of the Faraday rotator 6, the polarization direction of the back-propagating light no longer matches its transmission axis when returning to the polarization beam splitter 8. Therefore, it is reflected by the polarization beam splitter and led out of the cavity, thus achieving unidirectional light propagation.

[0031] In some preferred embodiments, the pump light output from the pump unit 1 is transmitted through the first cavity mirror 21 into the laser crystal 3.

[0032] In some preferred embodiments, the pump unit 1 includes a pump source 11, a spot shaping unit 12, and a focusing coupling unit 13 arranged sequentially. The pump source 11 generates pump light. The spot shaping unit 12 modulates the spatial energy distribution of the pump light, outputting a near-flat-top pump light distribution, thereby reducing the thermal gradient and thermal lensing effect within the laser crystal and improving the stability of Q-switched operation. The focusing coupling unit 13 is an aspherical focusing lens used to focus the pump light homogenized by the spot shaping unit 12 with low aberrations and couple it to the effective pump region of the laser crystal 3. Therefore, the pump beam waist position and spot size maintain good spatial overlap with the fundamental frequency oscillation mode region in the ring resonator. Consequently, the focusing coupling unit 13 can fully receive the pump light homogenized by the spot shaping unit 12 and perform low aberration focusing, reducing edge ray truncation and spherical aberration effects. This allows the pump light to form a pump spot with controllable size and relatively uniform distribution in the effective pumping region of the laser crystal, thereby improving the spatial overlap efficiency between the pump light and the fundamental frequency oscillation mode region, reducing local thermal deposition peaks, weakening thermal lensing effect and thermal birefringence, and improving the stability and repeatability of Q-switched output.

[0033] Preferably, the focal length of the aspherical focusing lens can be 30mm-100mm, the effective aperture can be 10mm-30mm, and the numerical aperture can be 0.05-0.20; the exit divergence half-angle of the microlens array homogenizer can be 2°-8°, and the target pump spot radius within the laser crystal can be 0.2mm-0.8mm. Within this range, the pump beam waist position and spot size maintain good spatial overlap with the fundamental frequency oscillation mode region within the ring resonator.

[0034] Preferably, the spot shaping unit 12 includes a collimation unit 121 and a spot shaping component 122 arranged sequentially along the light propagation direction. The spot shaping component 122 includes a plurality of microlens homogenizers spaced apart along the light propagation direction, used to divide the incident beam collimated by the collimation unit 121 into multiple sub-beams, and to form a spot with uniform intensity distribution after the multiple sub-beams pass through the focusing coupling unit. This reduces the thermal deposition peak in local areas within the laser crystal, weakens the thermal gradient, thermal lensing effect, and thermally induced birefringence caused by pump inhomogeneity, and simultaneously provides a more uniform fundamental frequency light field distribution for the intracavity frequency doubling crystal.

[0035] Preferably, such as Figure 3 As shown, the light spot shaping component 122 includes a first microlens array 1221 and a second microlens array 1222 arranged sequentially along the light propagation direction; the first microlens array 1221 is used to divide the incident light beam collimated by the collimating unit 121 into multiple sub-beams, and the second microlens array 1222 is used to modulate the propagation direction of the multiple sub-beams, so that the multiple sub-beams are superimposed on the surface of the first cavity mirror 21 after passing through the focusing coupling unit 13, forming a light spot with uniform light intensity distribution.

[0036] More preferably, the first microlens array 1221 and the second microlens array 1222 are spaced apart along the optical axis, and their microlens units correspond to each other. Preferably, the first microlens array 1221 and the second microlens array 1222 are spaced apart along the optical axis, and the number of their microlens units corresponds to their lateral positions, that is, the number of their microlens units is the same, and the optical axes of the corresponding microlens units are collinear. The axial distance between the first microlens array 1221 and the second microlens array 1222 is 0.8 to 1.2 times the focal length of the microlens array.

[0037] Preferably, the focusing coupling unit 13 is an aspherical focusing lens.

[0038] In some preferred embodiments, a Brewster plate 9 is also included; the Brewster plate 9 is disposed in the optical path between the frequency doubling crystal 5 and the fourth cavity mirror 24. Based on the principle that the fundamental frequency light is forced to maintain p-polarization (parallel to the incident plane) by the Brewster plate 9 to improve frequency doubling efficiency and suppress polarization fluctuations, the fundamental frequency laser entering the frequency doubling crystal 5 is kept in a polarization state that meets the frequency conversion requirements, thereby improving frequency doubling efficiency and reducing the impact of polarization instability on the frequency conversion process. In some preferred embodiments, such as Figure 2 As shown, it also includes a non-polarizing beam splitter 101, a dual-wavelength λ / 2 waveplate 102, a frequency combining crystal 103, and a dichroic mirror 104, which are sequentially arranged on the transmission optical path of the fourth cavity mirror 24. The non-polarizing beam splitter 101 is used to split the input light into at least two paths, one of which passes through the dual-wavelength λ / 2 waveplate 102, the frequency combining crystal 103, and the dichroic mirror 104. The dual-wavelength λ / 2 waveplate 102 is used to rotate and align the linear polarization directions of the fundamental frequency light and the frequency-doubled light in the input light, so that their polarization directions are precisely aligned with the o-axis and e-axis of the frequency combining crystal. The dichroic mirror 104 is used to separate and export the third wavelength light in the output light of the frequency combining crystal 103. Both beams output from the fourth cavity mirror 24 are linearly polarized, so joint polarization adjustment can be achieved through the same dual-wavelength λ / 2 waveplate 102. The dual-wavelength λ / 2 waveplate 102 is used to simultaneously rotate and align the linear polarization directions of the fundamental and frequency-doubled beams, so that their polarization directions are precisely aligned with the o-axis and e-axis of the frequency combining crystal 103, thereby satisfying the polarization matching conditions required for the frequency combining process. When the phase matching conditions are met, the fundamental and frequency-doubled beams undergo a frequency combining process in the frequency combining crystal 103 to generate a third-wavelength frequency-doubled laser. A dichroic mirror 104 is set after the frequency combining crystal 103 to separate and export the third-wavelength frequency-doubled laser from the remaining fundamental and frequency-doubled beams, thereby realizing the spatial separation and independent output of multi-wavelength lasers.

[0039] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupled cavity mirror structure, characterized in that, Includes pump unit, ring resonator, laser crystal, acousto-optic Q-switcher and frequency doubling crystal; The pumping unit is used to emit pump light to the laser crystal to excite the laser crystal to generate fundamental frequency light; The ring resonant cavity includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror arranged sequentially along the light propagation direction; The laser crystal is disposed in the optical path between the first cavity mirror and the second cavity mirror; The acousto-optic Q-switcher and the frequency doubling crystal are sequentially arranged in the optical path between the third cavity mirror and the fourth cavity mirror, and the third cavity mirror is a fundamental frequency high-reflection and frequency doubling low-reflection mirror; The fourth cavity mirror is a high-frequency lens that partially reflects the fundamental frequency light.

2. The ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, The installation angle of the fourth cavity mirror is b, 1 / 2arctan ≤ b ≤ Among them, 2w 2ω ≤Δ≤3w 2ω w 2ω The frequency-doubled light at the frequency-doubled crystal is 1 / e 2 The light spot radius, S4 is the distance from the frequency doubling crystal to the fourth cavity mirror. This refers to the maximum allowable installation tilt angle of the fourth cavity mirror in its working state; And / or, the mounting angle of the third laparoscope is α, 1 / 2arctan-b≤a≤ Where S3 is the distance from the third cavity mirror to the frequency doubling crystal. This is the maximum allowable installation tilt angle for the third cavity mirror in its working state.

3. The ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, The third cavity mirror has a fundamental frequency reflectivity ≥99% and a second-order frequency transmittance ≥95%; and / or, The fourth cavity mirror has a fundamental frequency light reflectivity of 90%-98% and a frequency-doubled light transmittance of 98%-99.9%.

4. The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, It also includes Faraday rotators, quarter-wave plates, and polarizing beam splitters; The Faraday rotator, the quarter-wave plate, and the polarization beam splitter are sequentially arranged in the optical path between the acousto-optic Q-switcher and the frequency doubling crystal; The Faraday rotator is used to rotate the polarization direction by 45°; The polarization direction of the polarization beam splitter is the same as that of the fundamental frequency light.

5. The ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, The pump light output from the pump unit is transmitted through the first cavity mirror and enters the laser crystal.

6. The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, The pumping unit includes a pump source, a spot shaping unit, and a focusing coupling unit arranged in sequence. The pump source is used to generate pump light; The spot shaping unit is used to modulate the spatial energy distribution of the pump light and output a near-flat-top pump light. The focusing coupling unit is used to focus the pump light after it has been homogenized by the spot shaping unit with low aberration and couple it to the effective pump region of the laser crystal.

7. The ring-type Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 6, characterized in that, The spot shaping unit includes a collimation unit, a spot shaping component, and a focusing coupling unit arranged sequentially along the light propagation direction; The light spot shaping component includes multiple microlens homogenizers spaced apart in the light propagation direction, used to divide the incident light beam after collimation by the collimation unit into multiple sub-beams, and to form a light spot with uniform light intensity distribution after the multiple sub-beams pass through the focusing coupling unit.

8. The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 6, characterized in that, The focusing coupling unit is an aspherical focusing lens.

9. The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, Also includes Brewster films; The Brewster plate is positioned in the optical path between the frequency doubling crystal and the fourth cavity mirror.

10. The ring-shaped Q-switched multi-wavelength solid-state laser with a wavelength decoupling cavity mirror structure according to claim 1, characterized in that, It also includes a non-polarizing beam splitter, a dual-wavelength λ / 2 waveplate, a frequency combining crystal, and a dichroic mirror, which are sequentially arranged on the transmission optical path of the fourth cavity mirror; The non-polarizing beam splitter is used to split the input light into at least two paths, one of which passes through the dual-wavelength λ / 2 waveplate, the frequency combining crystal, and the dichroic mirror. The dual-wavelength λ / 2 waveplate is used to rotate and align the linear polarization directions of the fundamental and frequency-doubled light in the input light, so that their polarization directions are precisely aligned with the o-axis and e-axis of the frequency combining crystal. The dichroic mirror is used to separate and extract the third wavelength light from the output light of the combining crystal.

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