A polarization-tunable green laser

Abstract

The present invention proposes a polarization-adjustable green laser, which relates to the technical field of solid lasers, and includes a pump source, a laser crystal, a Q switch, and a polarization adjustment module. The pump light output by the pump source is incident on the laser crystal, so that the laser crystal outputs excitation light, and the excitation light is input into the Q switch to generate pulse light, and the pulse light is input into the polarization adjustment module; the polarization adjustment module includes a first beam splitter, a first self-frequency doubling crystal, a second self-frequency doubling crystal, a first temperature control unit connected to the first self-frequency doubling crystal, a second temperature control unit connected to the second self-frequency doubling crystal, and a reflector, and the first temperature control unit and the second temperature control unit are used to control the temperature of the first self-frequency doubling crystal and the second self-frequency doubling crystal, respectively, so that the polarization adjustment module outputs a green light beam with a continuously changing polarization direction. The present invention is helpful to generate green with a continuously changing polarization direction.

Description

Technical Field

[0001] The invention relates to the technical field of solid lasers, and in particular to a polarization-adjustable green laser. Background Art

[0002] Laser is one of the major inventions in modern science and technology. Among them, the end-pumped 532nm band laser is used in the field of cold processing, and its application value in metal, non-metal and precision processing is particularly prominent. Since end pumping can obtain higher beam quality, obtaining end-pumped green laser with excellent beam quality and long-term stable operation is of great significance to the growing laser processing industry.

[0003] The Chinese patent with the publication number CN116722429B discloses a long pulse width green laser with high beam quality, comprising: a semiconductor laser, a coupling lens group, a first fundamental frequency light reflector, a Q-switching device, a second fundamental frequency light reflector, a laser crystal, a compensation lens, a dichroic mirror, a self-frequency doubling crystal and a dual-wavelength reflector; the first fundamental frequency light reflector, the second fundamental frequency light reflector, the compensation lens, the dichroic mirror and the dual-wavelength reflector constitute a resonant cavity for generating fundamental frequency light oscillation, and the laser pulse emitted by the semiconductor laser passes through the resonant cavity and then outputs a green light beam by the dichroic mirror. The above-mentioned long pulse width green laser can only realize vertical polarization or perpendicular polarization of the green light beam alone, therefore, it is very necessary to provide a polarization-adjustable green laser to provide a green light beam with a continuously changing polarization direction. Summary of the invention

[0004] In view of this, the present invention proposes a polarization-adjustable green light laser, which controls the temperatures of the first self-frequency doubling crystal and the second self-frequency doubling crystal in real time by means of a first temperature control unit and a second temperature control unit arranged corresponding to the first self-frequency doubling crystal and the second self-frequency doubling crystal, so as to change the polarization matching of the pulse light of the first self-frequency doubling crystal and the second self-frequency doubling crystal, so as to output a green light beam with a continuously changing polarization direction.

[0005] The present invention provides a polarization-adjustable green laser, comprising a pump source, a laser crystal arranged in the light-emitting direction of the pump source, a Q switch, and a polarization adjustment module, wherein:

[0006] The pump light output by the pump source is incident on the laser crystal, so that the laser crystal outputs excitation light, and the excitation light generates pulse light after being input into the Q switch, and the pulse light is input into the polarization adjustment module;

[0007] The polarization adjustment module includes a first beam splitter, a first self-frequency doubling crystal, a second self-frequency doubling crystal, a first temperature control unit connected to the first self-frequency doubling crystal, a second temperature control unit connected to the second self-frequency doubling crystal, and a reflector. The first beam splitter, the first self-frequency doubling crystal, the second self-frequency doubling crystal, and the reflector are all arranged in the light emitting direction of the pump source. The first temperature control unit and the second temperature control unit are respectively used to adjust the temperature of the first self-frequency doubling crystal and the second self-frequency doubling crystal, so that the polarization matching of the pulse light input to the first self-frequency doubling crystal and the second self-frequency doubling crystal changes, so that the polarization adjustment module outputs a green light beam with a continuously changing polarization direction.

[0008] On the basis of the above technical solution, preferably, it includes a collimator, a focusing mirror and a dichroic mirror arranged in the light emitting direction of the pump source, and the collimator, the focusing mirror and the dichroic mirror are all arranged between the pump source and the laser crystal.

[0009] On the basis of the above technical solution, preferably, the cutting angles of the first self-frequency doubling crystal and the second self-frequency doubling crystal are both θ=90° and φ=10.4°.

[0010] More preferably, the axial direction of the first self-frequency doubling crystal and the axial direction of the second self-frequency doubling crystal are perpendicular to each other.

[0011] More preferably, the laser crystal is a neodymium-doped yttrium aluminum garnet crystal, and the first self-frequency doubling crystal and the second self-frequency doubling crystal are both lithium triborate crystals.

[0012] More preferably, the method further comprises a second beam splitter arranged corresponding to the first beam splitter, wherein the second beam splitter is used for deriving the green light beam.

[0013] More preferably, the light incident surface of the dichroic mirror is coated with an anti-reflection film of 808 nm band, and the light emitting surface of the dichroic mirror is coated with an anti-reflection film of 808 nm band and a high-reflection film of 1064 nm band.

[0014] More preferably, the light incident surface of the first beam splitter is coated with an anti-reflection film of the 1064nm band, and the light emitting surface of the first beam splitter is coated with an anti-reflection film of the 1064nm band and a high-reflection film of the 532nm band.

[0015] More preferably, the end face of the reflector close to the second self-frequency doubling crystal is coated with a high-reflection film in the 532nm band and the 1064nm band.

[0016] More preferably, the pump source is any one of a semiconductor laser, a solid laser or a fiber laser.

[0017] The polarization-adjustable green laser provided by the present invention has the following beneficial effects compared with the prior art:

[0018] (1) The temperatures of the first self-frequency doubling crystal and the second self-frequency doubling crystal are controlled in real time by means of a first temperature control unit and a second temperature control unit which are arranged corresponding to the first self-frequency doubling crystal and the second self-frequency doubling crystal. When the first self-frequency doubling crystal and the second self-frequency doubling crystal are both in matching state at the same time, the two self-frequency doubling crystals output a polarization state close to 1:1. When the first self-frequency doubling crystal or the second self-frequency doubling crystal is far from the matching temperature, the self-frequency doubling crystal with the original matching temperature is maintained as the main output to realize the output of the doubled light which is mainly horizontally polarized light or vertically polarized light, thereby realizing the change of the polarization matching of the pulse light of the first self-frequency doubling crystal and the second self-frequency doubling crystal, and achieving the purpose of outputting a green light beam with continuously changing polarization direction;

[0019] (2) The laser crystal adopts a neodymium-doped yttrium aluminum garnet crystal, which can maintain a slightly strong absorption capacity in the 800-900nm band, and can significantly improve the conversion efficiency while ensuring that the bandwidth is not attenuated. The first self-frequency doubling crystal and the second self-frequency doubling crystal adopt the same cutting method θ=90°, φ=10.4°, so that the fundamental frequency light achieves a type of phase matching, which can significantly improve the conversion efficiency while ensuring that the doubled frequency bandwidth is not attenuated, so that the first self-frequency doubling crystal and the second self-frequency doubling crystal can better convert the 1064nm fundamental frequency light into 532nm doubled frequency light at this cutting angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the optical path of a polarization-tunable green laser provided by the present invention.

[0022] Explanation of the accompanying drawings: 1. Pump source; 2. Laser crystal; 3. Q switch; 4. Polarization adjustment module; 41. First beam splitter; 42. First self-frequency doubling crystal; 43. Second self-frequency doubling crystal; 44. First temperature control unit; 45. Second temperature control unit; 46. Reflector; 5. Collimator; 6. Focusing mirror; 7. Dichroic mirror; 8. Second beam splitter. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Before introducing the embodiments of the present invention, some terms involved in the embodiments of the present invention are first defined and explained.

[0025] Nonlinear optical effect: a phenomenon generated by electromagnetic radiation, but its response is not proportional to the illumination. In it, incident light of a certain frequency can be converted into light of other frequencies through interaction with the medium, that is, in addition to the original frequency ω, higher harmonics such as 2ω and 3ω will appear, and a series of light of different frequencies and intensities distributed periodically on the spectrum can also be generated.

[0026] The terms "high reflection" and "high transmittance" in the present invention have well-known meanings in the art. "High reflection" means that the reflectivity of incident light of a specific wavelength or wavelength band is greater than 99%. "High transmittance" means that the transmittance of incident light of a specific wavelength or wavelength band is greater than 95%.

[0027] See also Figure 1 The present invention provides a polarization-adjustable green laser, comprising a pump source 1, a laser crystal 2, a Q switch 3 and a polarization adjustment module 4 arranged in the light-emitting direction of the pump source 1, wherein:

[0028] The pump source 1 is used to emit pump light and provide energy for the laser crystal 2, wherein the pump source 1 is a continuous wave laser, and the excitation mode of the continuous wave laser can be semiconductor laser excitation or solid-state laser excitation. The pump source 1 is any one of a semiconductor laser, a solid-state laser or a fiber laser.

[0029] The laser crystal 2 is used to convert the pump light output by the pump source 1 into the excitation light, wherein the wavelengths of the pump light and the excitation light are different. Since the laser crystal 2 is a neodymium-doped yttrium aluminum garnet crystal, the Nd ion doping concentration in the laser crystal 2 can be selected according to the laser requirements, and the neodymium-doped yttrium aluminum garnet crystal (Nd:YAG) maintains a slightly strong absorption capacity in the 800-900nm band, which can significantly improve the conversion efficiency while ensuring that the bandwidth is not attenuated, so that the laser crystal 2 has a better conversion efficiency of converting the 808nm band pump light into the 1064nm band excitation light.

[0030] In one example, the pump light may be a light beam with a wavelength of 808 nm emitted by a semiconductor laser, a solid laser, or a fiber laser, and the excitation light may be a light beam with a wavelength of 1064 nm generated by the pump light excited by the laser crystal 2 .

[0031] Q switch 3 is used to modulate the excitation light to generate pulsed light. Q switch 3 controls the resonant channel of light by adjusting the quality factor (Q value) of the laser cavity, thereby inhibiting or allowing the generation of laser pulses. The function of Q switch 3 is to quickly reduce the energy of the photons initially excited when necessary, thereby generating high-energy, short pulses. Q switch 3 can quickly switch between very small or very high losses in the laser beam to achieve efficient laser pulse output, that is, it can generate pulses with pulse widths ranging from microseconds to nanoseconds, and the repetition frequency is usually around kilohertz. By applying a suitable voltage, the state switching of the resonant cavity is quickly achieved, thereby generating high-quality laser pulse output.

[0032] In this embodiment, the pump light output by the pump source 1 is incident on the laser crystal 2 so that the laser crystal 2 outputs excitation light, and the excitation light is input into the Q switch 3 to generate pulse light, and the pulse light is input into the polarization adjustment module 4.

[0033] Preferably, the green laser comprises a collimator 5, a focusing mirror 6 and a dichroic mirror 7 arranged in the light emitting direction of the pump source 1, and the collimator 5, the focusing mirror 6 and the dichroic mirror 7 are all arranged between the pump source 1 and the laser crystal 2. The light incident surface of the dichroic mirror 7 is plated with an anti-reflection film of the 808nm band, and the light emitting surface of the dichroic mirror 7 is plated with an anti-reflection film of the 808nm band and a high reflection film of the 1064nm band.

[0034] In one example, the collimator 5 is used to collimate the pump source 1. The collimator 53 is a plano-convex lens with a size parameter of D30-F100, a light-emitting surface of R416.73, a center thickness of 4.6 mm, and an edge thickness of 2.05 mm. The focusing lens 6 is used to focus the collimated pump light and transfer the energy to the laser crystal 2. The focusing lens 6 is a plano-convex lens with a size parameter of D30-F100, a light-emitting surface of R134.35, a center thickness of 3.5 mm, and an edge thickness of 2.66 mm. The dichroic mirror 7 is coated with an anti-reflection film in the 808 nm band on both sides, and a high-reflection film in the 1064 nm band on the right end face, which is used to transfer the pump light to the laser crystal 2.

[0035] In one example, the collimating lens 5 and the focusing lens 6 are lenses with a coupling ratio of 1:2, the focal length of the collimating lens 5 is 20 mm, and the focal length of the focusing lens 6 is 40 mm.

[0036] In one example, the collimating mirror 5 and the focusing mirror 6 are collimated and then focused to the end face of the laser crystal 2, the dichroic mirror 7 and the reflector 46 form a resonant cavity, and the laser crystal 2, the Q switch 3, the first self-frequency doubling crystal 42, and the second self-frequency doubling crystal 43 are placed in the resonant cavity to form an intracavity frequency doubling Q-switched laser. The laser crystal 2 adopts Nd:YAG crystal (neodymium-doped yttrium aluminum garnet crystal) with non-polarization output characteristics, and the polarization state of the 1064nm fundamental frequency light generated is random. Among them, the dichroic mirror 7 can adopt a plano-convex dichroic mirror, and the resonant cavity formed by the dichroic mirror 7 and the reflector 46 belongs to an unstable cavity, and the curvature is generally R100~1000.

[0037] The polarization adjustment module 4 includes a first beam splitter 41, a first self-frequency doubling crystal 42, a second self-frequency doubling crystal 43, a first temperature control unit 44 connected to the first self-frequency doubling crystal 42, a second temperature control unit 45 connected to the second self-frequency doubling crystal 43, and a reflector 46. The first beam splitter 41, the first self-frequency doubling crystal 42, the second self-frequency doubling crystal 43 and the reflector 46 are all arranged in the light emitting direction of the pump source 1. The first temperature control unit 44 and the second temperature control unit 45 are respectively used to adjust the temperature of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43, so that the polarization matching of the pulse light input to the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 changes, so that the polarization adjustment module 4 outputs a green light beam with a continuously changing polarization direction.

[0038] The light incident surface of the first beam splitter 41 is coated with an anti-reflection film of the 1064nm band, and the light emitting surface of the first beam splitter 41 is coated with an anti-reflection film of the 1064nm band and a high-reflection film of the 532nm band. The first beam splitter 41 is used to separate pulse light and frequency-doubled light, and export the frequency-doubled light.

[0039] The first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both lithium triborate crystals (LBO), and the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both rectangular parallelepipeds. The above lithium triborate crystal (LBO) has a wide absorption range, that is, the lithium triborate crystal can have a sufficiently large nonlinear optical coefficient in the wavelength range of 165 to 3200 nm, and can achieve phase matching at room temperature. In addition, the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 can also be selected from lithium niobate (LiNbO3), barium metaborate (BBO), lithium cesium borate (LiCsB6O10) and potassium boroberylate fluoride (KBBF) and other self-frequency doubling crystals.

[0040] The axial direction of the first self-frequency doubling crystal 42 and the axial direction of the second self-frequency doubling crystal 43 are perpendicular to each other, and the cutting angles of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both θ=90° and φ=10.4°. And the lithium triborate crystal is a nonlinear crystal, and the direction of the crystal optical axis is usually defined as the Z direction. According to the right-hand spiral criterion of the coordinate system, the X and Y direction coordinate axes of the crystal are determined. θ is the angle between the wave vector k and the crystal optical axis, which is the incident angle of the pump light on the crystal, that is, the pump light is perpendicular to the crystal end face. When the first self-frequency doubling crystal 42 is cut along the X direction and the second self-frequency doubling crystal 43 is cut along the Y direction, the cutting angle is θ=90°, at which time the non-critical phase condition is met and the nonlinear coefficient is maximum. That is, the best crystal phase matching direction of the 532nm band is cut so that the fundamental frequency light achieves a type of phase matching, which can significantly improve the conversion efficiency while ensuring that the double frequency bandwidth is not attenuated, so that the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 can better convert the 1064nm fundamental frequency light into 532nm double frequency light at this cutting angle.

[0041] The first temperature control unit 44 is used to precisely control the temperature of the first self-frequency doubling crystal 42 to adjust the frequency doubling matching degree of the first self-frequency doubling crystal 42 ; the second temperature control unit 45 is used to precisely control the temperature of the second self-frequency doubling crystal 43 to adjust the frequency doubling matching degree of the second self-frequency doubling crystal 43 .

[0042] The reflector 46 is used to reflect the doubled frequency light and pulse light generated by the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 , so the end surface of the reflector 46 close to the second self-frequency doubling crystal 43 is plated with a high reflection film in the 532nm band and the 1064nm band.

[0043] In one example, the reflector 46 can be set as a concave mirror, and the curvature radius of the concave mirror is 50-1000 mm. In the resonant cavity formed by the dichroic mirror 7 and the reflector 46, the concave mirror is selected as the reflector 46, which is conducive to the oscillation of the fundamental frequency light in the resonant cavity. The curvature radius is selected to be 50-1000 mm. The larger the curvature radius, the more times the fundamental frequency light oscillates reflected to the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43, so as to increase the absorption efficiency of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 for the fundamental frequency light. The distance between the dichroic mirror 7 and the reflector 46 is selected to be 15-200 mm, which is conducive to the oscillation of the fundamental frequency light.

[0044] In this embodiment, by designing a type I phase matching 1064(o)+1064(o)→532(e), an angle phase matching LBO crystal, temperature matching at room temperature can be achieved. The first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both cut with θ=90° and φ=10.4°, corresponding to an optimal matching temperature of 50°C. The first self-frequency doubling crystal 42 is placed with the x-axis facing the horizontal direction, and is used to receive horizontally polarized 1064nm fundamental frequency light and generate vertically polarized 532nm doubled frequency light. The second self-frequency doubling crystal 43 is placed with the x-axis facing the vertical direction, and is used to receive vertically polarized 1064nm fundamental frequency light and generate horizontally polarized 532nm doubled frequency light. The 532nm doubled frequency light is derived through the first beam splitter 41. The beam splitter is coated with an anti-reflection film in the 1064nm band on both sides, and a high-reflection film in the 532nm band is coated on the light-emitting surface without polarization characteristics. The first temperature control unit 44 and the second temperature control unit 45 respectively control the working temperature of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43. When the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both controlled at 50°C, the two LBO crystals are optimally matched. At this time, the directional polarization competition of the two LBO crystals is consistent, and there will be a polarization state output close to 1:1. When the temperature control of the first self-frequency doubling crystal 42 is far away from 50°C and the second self-frequency doubling crystal 43 is kept at 50°C, the second self-frequency doubling crystal 43 has a large competitive advantage and outputs 532nm band doubled frequency light with horizontal polarization as the main light. When the first self-frequency doubling crystal 42 is kept at 50°C and the second self-frequency doubling crystal 43 is kept at 50°C, the first self-frequency doubling crystal 42 has a large competitive advantage and outputs 532nm band doubled frequency light with vertical polarization as the main light. That is, by reasonably setting the temperature of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43, a 532nm laser with continuously changing polarization output can be obtained.

[0045] The green laser also includes a second beam splitter 8 corresponding to the first beam splitter 41, and the second beam splitter 8 is used to derive a green light beam. The right end surface of the second beam splitter 8 is plated with a high-reflection film in the 532nm band to derive a 532nm doubled frequency light.

[0046] The present invention controls the temperature of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 in real time by means of the first temperature control unit 44 and the second temperature control unit 45 which are arranged corresponding to the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43. When the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43 are both in matching state at the same time, the two self-frequency doubling crystals output a polarization state close to 1:1. When the first self-frequency doubling crystal 42 or the second self-frequency doubling crystal 43 is far away from the matching temperature, the self-frequency doubling crystal with the original matching temperature is maintained as the main output to realize the output of the doubled light which is mainly horizontally polarized light or vertically polarized light, thereby realizing the change of the polarization matching of the pulse light of the first self-frequency doubling crystal 42 and the second self-frequency doubling crystal 43, and achieving the purpose of outputting a green light beam with continuously changing polarization direction.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polarization-tunable green laser, It is characterized in that It comprises a pump source (1), a laser crystal (2) arranged in the light emitting direction of the pump source (1), a Q switch (3) and a polarization adjustment module (4), wherein: The pump light output by the pump source (1) is incident on the laser crystal (2), so that the laser crystal (2) outputs excitation light, and the excitation light is input into the Q switch (3) to generate pulse light, and the pulse light is input into the polarization adjustment module (4); The polarization adjustment module (4) comprises a first beam splitter (41), a first self-frequency doubling crystal (42), a second self-frequency doubling crystal (43), a first temperature control unit (44) connected to the first self-frequency doubling crystal (42), a second temperature control unit (45) connected to the second self-frequency doubling crystal (43), and a reflector (46); the first beam splitter (41), the first self-frequency doubling crystal (42), the second self-frequency doubling crystal (43), and the reflector (46) are all arranged in the light emitting direction of the pump source (1); the first temperature control unit (44) and the second temperature control unit (45) are respectively used to adjust the temperature of the first self-frequency doubling crystal (42) and the second self-frequency doubling crystal (43) so that the polarization matching of the pulse light input to the first self-frequency doubling crystal (42) and the second self-frequency doubling crystal (43) is changed, so that the polarization adjustment module (4) outputs a green light beam with a continuously changing polarization direction; The cutting angles of the first self-frequency doubling crystal (42) and the second self-frequency doubling crystal (43) are both θ=90° and φ=10.4°; The axial direction of the first self-frequency doubling crystal (42) and the axial direction of the second self-frequency doubling crystal (43) are perpendicular to each other.

2. The polarization-tunable green laser according to claim 1, It is characterized in that It comprises a collimator (5), a focusing mirror (6) and a dichroic mirror (7) which are arranged in the light emitting direction of the pump source (1), and the collimator (5), the focusing mirror (6) and the dichroic mirror (7) are all arranged between the pump source (1) and the laser crystal (2).

3. The polarization-tunable green laser according to claim 1, It is characterized in that The laser crystal (2) is a neodymium-doped yttrium aluminum garnet crystal, and the first self-frequency doubling crystal (42) and the second self-frequency doubling crystal (43) are both lithium triborate crystals.

4. The polarization-tunable green laser according to claim 1, It is characterized in that It also comprises a second beam splitter (8) arranged corresponding to the first beam splitter (41), wherein the second beam splitter (8) is used to derive the green light beam.

5. The polarization-tunable green laser according to claim 2, It is characterized in that The light incident surface of the dichroic mirror (7) is coated with an anti-reflection film of the 808 nm band, and the light exiting surface of the dichroic mirror (7) is coated with an anti-reflection film of the 808 nm band and a high-reflection film of the 1064 nm band.

6. The polarization-tunable green laser according to claim 5, It is characterized in that The light incident surface of the first beam splitter (41) is coated with an anti-reflection film of the 1064 nm band, and the light emitting surface of the first beam splitter (41) is coated with an anti-reflection film of the 1064 nm band and a high-reflection film of the 532 nm band.

7. The polarization-tunable green laser according to claim 6, It is characterized in that The end surface of the reflector (46) close to the second self-frequency doubling crystal (43) is plated with a high-reflection film in the 532 nm band and the 1064 nm band.

8. The polarization-tunable green laser according to any one of claims 1 to 7, It is characterized in that The pump source (1) is any one of a semiconductor laser, a solid laser or a fiber laser.

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