High-efficiency all-solid-state quasi-continuous green laser

Abstract

The invention discloses a high-efficiency all-solid-state quasi-continuous green laser, and belongs to the technical field of lasers. The laser comprises a first dual-wavelength high-reflectivity mirror, a first Q-switch, a first LD side pumping module, a second dual-wavelength high-reflectivity mirror, a quartz rotator, a third dual-wavelength high-reflectivity mirror, a second LD side pumping module, a second Q-switch, a diaphragm, a harmonic output mirror, a frequency doubling crystal and a fourth dual-wavelength high-reflectivity mirror. The first dual-wavelength high-reflectivity mirror, the second dual-wavelength high-reflectivity mirror, the third dual-wavelength high-reflectivity mirror, the harmonic output mirror and the fourth dual-wavelength high-reflectivity mirror form a resonant cavity. An intracavity frequency doubling scheme is adopted, the frequency doubling crystal is placed in a laser resonant cavity for frequency doubling, frequency doubling light is directly output from the resonant cavity, the LBO frequency doubling crystal abuts against the 45-degree harmonic output mirror so that the frequency doubling efficiency can be maximized, and hectowatt-level green light output can be achieved by matching the double LD side pumps and the double Q-switched switches with the 90-degree quartz rotator.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a high-efficiency all-solid-state quasi-continuous green laser. Background Technology

[0002] With the significant development of semiconductor laser technology, solid-state laser materials, and frequency conversion technology, all-solid-state lasers (Diode Pumped Solid State Laser, DPSSL) have gradually emerged. This laser integrates multiple advantages of semiconductor lasers and solid-state lasers, exhibiting high energy conversion efficiency, low pump threshold power, compact design structure, stable operating performance, long lifespan, and excellent beam quality.

[0003] In particular, high-average-power, high-repetition-rate laser diode-pumped green solid-state lasers possess advantages such as high efficiency, long lifespan, compact structure, and good beam quality, and have wide applications in laser processing, laser medicine, laser performance, lidar, laser communication, and laser spectroscopy. As industrial applications continuously demand higher laser processing effects and efficiency, the market's requirements for laser output power, emission wavelength, and output pulse width are also increasing. High-power, high-beam-quality green lasers, due to their short wavelength and high power, have unique advantages in materials analysis, printed circuit board drilling and cutting, semiconductor material irradiation processing, and ceramic cutting applications.

[0004] Currently, all-solid-state green lasers have become a relatively mature and rapidly developing important category in the field of all-solid-state lasers. These lasers primarily use Nd:YAG or Nd:YVO as the laser medium, initially generating a 1064nm near-infrared fundamental frequency output. Depending on the application, they can be categorized as continuous or quasi-continuous output. Subsequently, nonlinear frequency transformation is performed using nonlinear crystals such as KTP, LBO, and BBO, employing intracavity or extracavity frequency doubling methods to achieve a 532nm green laser output. They demonstrate broad application potential in various fields, including laser medicine, laser pump sources, laser demonstrations, laser precision machining, and isotope separation.

[0005] The common approach to obtaining high-frequency-doubling efficiency green laser light is through intracavity frequency doubling, which involves placing a frequency-doubling crystal inside a resonant cavity. The high power density within the laser resonant cavity allows for efficient frequency doubling. However, this method suffers from poor stability, and power increases are limited by the oscillator, making it difficult to achieve high-power, high-energy laser output. Therefore, further optimization of intracavity frequency doubling technology is needed to develop a novel, high-efficiency all-solid-state quasi-continuous green laser. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high-efficiency all-solid-state quasi-continuous green laser. This device effectively solves the problems of unstable output power and limited frequency doubling efficiency in all-solid-state green lasers, achieving efficient frequency doubling and stable pulse output.

[0007] The technical solution of the present invention is as follows: A high-efficiency all-solid-state green laser includes a first dual-wavelength high-reflection mirror, a first Q-switching switch, a first LD side-pumping module, a second dual-wavelength high-reflection mirror, a quartz rotator, a third dual-wavelength high-reflection mirror, a second LD side-pumping module, a second Q-switching switch, an aperture, a harmonic output mirror, a frequency doubling crystal, and a fourth dual-wavelength high-reflection mirror. The first dual-wavelength high-reflection mirror, the second dual-wavelength high-reflection mirror, the third dual-wavelength high-reflection mirror, the harmonic output mirror, and the fourth dual-wavelength high-reflection mirror constitute a resonant cavity.

[0008] According to a preferred embodiment of the present invention, the first dual-wavelength high-reflection mirror has a 0° reflection and is set perpendicular to the horizontal line; the second dual-wavelength high-reflection mirror has a 45° reflection and is set at a 45° angle to the horizontal line; the third dual-wavelength high-reflection mirror has a 45° reflection and is set at a 45° angle to the horizontal line; the harmonic output mirror is set parallel to the third dual-wavelength high-reflection mirror; and the fourth dual-wavelength high-reflection mirror has a 0° reflection and is set parallel to the horizontal line.

[0009] According to a preferred embodiment of the present invention, the first dual-wavelength high-reflection mirror, the second dual-wavelength high-reflection mirror, the third dual-wavelength high-reflection mirror, and the fourth dual-wavelength high-reflection mirror are coated with a 532nm high-reflection film and a 1064nm high-reflection film, which can achieve a high reflectivity of over 99% for fundamental frequency light and frequency-doubled light, reduce the possibility of laser leakage during resonance, and improve the safety of laser use.

[0010] According to a preferred embodiment of the present invention, the harmonic output mirror is coated with a 532nm high-transmittance film and a 1064nm high-reflection film, which can achieve high-efficiency output of frequency-doubled light.

[0011] According to a preferred embodiment of the present invention, both the first LD side-pumping module and the second LD side-pumping module are LD side-pumped Nd:YAG modules. This module uses a domestically produced 808nm semiconductor laser linear array as the pump source. By optimizing the structural parameters of the pump module and rationally controlling the doping concentration ratio in the laser crystal, the fluorescence uniformity of the laser crystal in a high-power pump environment can be improved, the volume of the fundamental mode component can be increased, and higher power fundamental frequency light output can be obtained while maintaining high beam quality. Furthermore, the design of the dual LD ​​side-pumping modules of the present invention can achieve higher power 1064nm laser output.

[0012] According to a preferred embodiment of the present invention, both the first Q-switching switch and the second Q-switching switch are acousto-optic Q-modulators. They are placed orthogonally in the resonant cavity, which can simultaneously turn off lasers from the horizontal and vertical directions. When the first Q-switching switch and the second Q-switching switch are driven synchronously, a higher turn-off capability can be achieved, and a higher Q-switching pulse output can be realized, laying the foundation for efficient frequency doubling output.

[0013] According to a preferred embodiment of the present invention, the quartz rotator is a 90° quartz rotator, forming a 0° angle with the horizontal line, and its function is to compensate for thermal effects. Under high-power operating conditions, the laser gain medium exhibits bifocal lens characteristics due to thermal effects, resulting in different focusing characteristics for radially and tangentially polarized light. To address this phenomenon, the present invention employs a double-rod structure composed of a first LD side-pump module and a second LD side-pump module, with a 90° quartz rotator inserted between them. This allows the phase difference between the radially and tangentially polarized light generated in the first laser rod to be effectively corrected in the second rod, thereby achieving the compensation effect for thermally induced distortion.

[0014] According to a preferred embodiment of the present invention, the aperture is a pinhole aperture, which serves to suppress higher-order transverse mode oscillations within the resonant cavity. In high-power scenarios, the power within the resonant cavity is high, and the laser gain is strong, making it easy for higher-order transverse mode lasers to oscillate, resulting in poor beam uniformity. By inserting a pinhole aperture of appropriate size, the oscillation of higher-order transverse modes within the cavity can be suppressed, which is beneficial to improving the beam quality of the output pulse.

[0015] According to a preferred embodiment of the present invention, the frequency doubling crystal is an LBO crystal, which possesses advantages such as a large nonlinear optical coefficient, a large acceptance angle, a small walk-off angle, a wide temperature and spectral bandwidth, a high photoelectric coefficient, a low dielectric constant, a high impedance ratio, and stable physical, chemical, and mechanical properties, as well as resistance to deliquescence. In particular, this crystal has a wide type I and type II temperature phase matching range, which can overcome the walk-off effect through temperature phase matching to achieve high frequency doubling efficiency.

[0016] In this invention, the seed laser emitted by the laser is generated by a first LD side-pumping module and a second LD side-pumping module. Specifically, the pump light, serving as the seed light, is emitted from a domestically produced 808nm semiconductor laser linear array within the pumping module. This pump light then enters from the side of the Nd:YAG gain medium in both pumping modules, providing energy to the Nd:YAG. After the energy of the pump light is absorbed by the Nd:YAG in the two pumping modules, particles within the crystal transition from the ground state to the excited state, resulting in population inversion. This process is then reflected by a first dual-wavelength high-reflection mirror, a second dual-wavelength high-reflection mirror, a third dual-wavelength high-reflection mirror, and a fourth dual-wavelength high-reflection mirror, achieving multiple oscillations and generating continuous 1064nm light. Simultaneously, a first Q-switching switch and a second Q-switching switch are placed within the resonant cavity. During the oscillation of continuous light within the cavity, the Q-switching switches, based on the acousto-optic effect, alter the refractive index of the Q-switching crystal, reducing the Q value (increasing cavity loss). This effectively shuts off the seed light oscillation, causing the Nd:YAG crystals of the two pump modules to accumulate a large number of inverted particles. When the particle number saturates, the Q value suddenly increases (low-loss state), triggering avalanche-induced stimulated emission and releasing a 1064nm fundamental frequency pulse light with high peak power. The fundamental frequency pulse light is then reflected by a harmonic output mirror and enters a frequency-doubling crystal. Based on the nonlinear effect under strong light, the 1064nm fundamental frequency light generates 532nm frequency-doubled light. After reflection by a dual-wavelength high-reflection mirror, the frequency-doubled light is output from the harmonic output mirror. Since 100% frequency doubling efficiency is not achieved, the remaining fundamental frequency light is reflected by the dual-wavelength high-reflection mirror and then frequency-doubled again by the frequency-doubling crystal before being output from the harmonic output mirror, achieving efficient frequency doubling output. Placing a 90° quartz rotator inside the cavity can compensate for the thermal effect of the laser crystal and achieve higher power output, while the aperture can suppress high-order transverse mode oscillations inside the cavity, which can further improve the beam quality and efficiency of the output laser pulse.

[0017] For any details not covered in this invention, please refer to the prior art.

[0018] Beneficial effects: 1. The high-efficiency all-solid-state quasi-continuous green laser provided by the present invention, through appropriate resonant cavity design and the use of suitable cavity structure, can achieve a large-angle adjustable resonant cavity mirror, thus ensuring the stability of the resonant cavity output.

[0019] 2. The high-efficiency all-solid-state quasi-continuous green laser provided by this invention is a quasi-continuous pulse output, adopting a dual acousto-optic Q-switching scheme. The two Q-switching switches are placed orthogonally, and the modulation voltage only needs to be a little over 100 volts. It is easy to use with continuous lasers for Q-switching, and can obtain giant pulses with peak power of several hundred kilowatts and kilohertz repetition frequency. It has the effect of turning off the laser in two-dimensional direction, and can achieve stable nanosecond-level pulse output with peak power of MW or more.

[0020] 3. The high-efficiency all-solid-state quasi-continuous green laser pumping method provided by this invention adopts a dual-LD side-pumping module. Its advantages lie in its simplicity and ease of implementation, providing high pump power. Pump power can be increased by increasing the number of side-pumping semiconductors or increasing the pump length. Furthermore, the large aspect ratio of the emission cross-section allows for easy matching with the laser medium, and the larger surface area facilitates heat dissipation. In addition, a 90° quartz rotator is incorporated into the dual-LD pumping method to compensate for birefringence caused by heating of a single laser rod, reducing the adverse effects of thermal effects on output power and beam quality in high-power scenarios. Simultaneously, a pinhole aperture structure suppresses higher-order transverse mode oscillations, achieving high beam quality and high-power laser output.

[0021] 4. The high-efficiency all-solid-state quasi-continuous green laser provided by this invention employs a frequency-doubling crystal selected from LBO crystals. This crystal possesses advantages such as a large nonlinear optical coefficient, a large acceptance angle, a small walk-off angle, a wide temperature and spectral bandwidth, a high photoelectric coefficient, a low dielectric constant, a high resistance ratio, and stable physical, chemical, and mechanical properties, as well as resistance to deliquescence. In particular, this crystal has a wide type I and type II temperature phase-matching range, which can overcome the walk-off effect through temperature phase matching to achieve high frequency doubling efficiency. The 532nm green light obtained through its frequency doubling has good beam quality, and the shortcomings of its relatively small effective nonlinear coefficient and frequency doubling efficiency can be compensated by increasing the length of the LBO crystal. Simultaneously, the LBO crystal has a high damage threshold and no "gray trail effect," making it widely applicable in high-stability, high-average-power, and high-peak-power all-solid-state frequency-doubling micro-optics.

[0022] 5. This invention adopts an intracavity frequency doubling scheme, placing the frequency doubling crystal inside the laser resonant cavity for frequency doubling. The frequency-doubled light is directly output from the resonant cavity. Furthermore, this invention places the LBO frequency doubling crystal close to the 45° harmonic output mirror to maximize the frequency doubling efficiency. With dual LD ​​side pumps, dual Q-switching switches, and a 90° quartz rotator, it can achieve 100-watt green light output. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the high-efficiency all-solid-state quasi-continuous green laser of the present invention.

[0024] In the figure: 1-First dual-wavelength high-reflection mirror, 2-First Q-switching switch, 3-First LD side pump module, 4-Second dual-wavelength high-reflection mirror, 5-Quartz rotator, 6-Third dual-wavelength high-reflection mirror, 7-Second LD side pump module, 8-Second Q-switching switch, 9-Aperture, 10-Harmonic output mirror, 11-Frequency doubling crystal, 12-Fourth dual-wavelength high-reflection mirror. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be further described below with reference to the accompanying drawings. However, this is not the only description; all matters not described in detail herein are based on conventional techniques in the art.

[0026] Example 1 like Figure 1 As shown, a high-efficiency all-solid-state green laser includes a first dual-wavelength high-reflection mirror 1, a first Q-switching switch 2, a first LD side-pumping module 3, a second dual-wavelength high-reflection mirror 4, a quartz rotator 5, a third dual-wavelength high-reflection mirror 6, a second LD side-pumping module 7, a second Q-switching switch 8, an aperture 9, a harmonic output mirror 10, a frequency doubling crystal 11, and a fourth dual-wavelength high-reflection mirror 12; The first dual-wavelength high-reflection mirror 1, the second dual-wavelength high-reflection mirror 4, the third dual-wavelength high-reflection mirror 6, the harmonic output mirror 10, and the fourth dual-wavelength high-reflection mirror 12 form a resonant cavity.

[0027] The first dual-wavelength high-reflection mirror 1 has a 0° reflection and is set perpendicular to the horizontal line; the second dual-wavelength high-reflection mirror 4 has a 45° reflection and is set at a 45° angle to the horizontal line; the third dual-wavelength high-reflection mirror 6 has a 45° reflection and is set at a 45° angle to the horizontal line; the harmonic output mirror 10 is set parallel to the third dual-wavelength high-reflection mirror 6. The fourth dual-wavelength high-reflection mirror 12 has a 0° reflection and is set parallel to the horizontal line. Both the first LD side-pumping module 3 and the second LD side-pumping module 7 are LD side-pumping Nd:YAG modules. Both the first Q-switching switch 2 and the second Q-switching switch 8 are acousto-optic Q-modulators, and they are orthogonally placed in the resonant cavity.

[0028] The quartz rotator is a 90° quartz rotator, forming a 0° angle with the horizontal. The frequency doubling crystal 11 is an LBO crystal.

[0029] In this embodiment, the seed laser emitted by the laser is generated by the first LD side pump module 3 and the second LD side pump module 7. Specifically, the pump light, serving as the seed light, is emitted from a domestically produced 808nm semiconductor laser linear array in the pump module. The pump light then enters from the side of the Nd:YAG gain medium in the two pump modules, providing energy to the Nd:YAG. After the energy of the pump light is absorbed by the Nd:YAG in the two pump modules, the particles in the crystal transition from the ground state to the excited state, forming a population inversion. This process is reflected by the first dual-wavelength high-reflection mirror 1, the second dual-wavelength high-reflection mirror 4, the third dual-wavelength high-reflection mirror 6, and the fourth dual-wavelength high-reflection mirror 12, resulting in multiple oscillations and generating 1064nm continuous light. Simultaneously, a first Q-switching switch 2 and a second Q-switching switch 8 are placed within the resonant cavity. During the oscillation of continuous light within the cavity, the Q-switches, based on the acousto-optic effect, alter the refractive index of the Q-switching crystal, reducing the Q value (increasing cavity loss). This effectively shuts off the seed light oscillation, causing the Nd:YAG crystals of the two pump modules to accumulate a large number of inverted particles. When the particle number saturates, the Q value suddenly increases (low-loss state), triggering avalanche-induced stimulated emission and releasing a 1064nm fundamental frequency pulse light with high peak power. The fundamental frequency pulse light is then reflected by the harmonic output mirror 10 and enters the frequency doubling crystal 11. Based on the nonlinear effect under strong light, the 1064nm fundamental frequency light generates 532nm frequency-doubled light. After reflection by the dual-wavelength high-reflection mirror 12, the frequency-doubled light is output from the harmonic output mirror 10. Since 100% frequency doubling efficiency is not achieved, the remaining fundamental frequency light is reflected by the dual-wavelength high-reflection mirror 12 and then frequency-doubled again by the frequency doubling crystal 11 before being output from the harmonic output mirror 10, achieving efficient frequency doubling output. The placement of a 90° quartz rotator 5 inside the cavity can compensate for the thermal effect of the laser crystal and achieve higher power output. The pinhole aperture 9 can suppress high-order transverse mode oscillations inside the cavity, which can further improve the beam quality and efficiency of the output laser pulse.

[0030] Example 2 A high-efficiency all-solid-state green laser has the structure described in Example 1, except that the first dual-wavelength high-reflection mirror 1, the second dual-wavelength high-reflection mirror 4, the third dual-wavelength high-reflection mirror 6, and the fourth dual-wavelength high-reflection mirror 12 are coated with 532nm high-reflection films and 1064nm high-reflection films, and the harmonic output mirror 10 is coated with 532nm high-transmittance films and 1064nm high-reflection films; the aperture 9 is a pinhole aperture.

[0031] In practical use, the seed laser emitted by the laser is generated by four dual-wavelength high-reflection mirrors combined with a dual-LD side-pumped module through multiple resonances. A dual acousto-optic Q modulator is placed inside the cavity. After continuous light is modulated by a Q-switched switch, pulsed light is output. The pulsed light with high peak power after Q-switching passes through a frequency doubling crystal LBO. Based on the nonlinear effect under strong light, laser frequency doubling output is achieved.

[0032] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A high-efficiency all-solid-state green laser, characterized in that, It includes a first dual-wavelength high-reflection mirror, a first Q-switching switch, a first LD side-pumping module, a second dual-wavelength high-reflection mirror, a quartz rotator, a third dual-wavelength high-reflection mirror, a second LD side-pumping module, a second Q-switching switch, an aperture, a harmonic output mirror, a frequency doubling crystal, and a fourth dual-wavelength high-reflection mirror; The first dual-wavelength high-reflection mirror, the second dual-wavelength high-reflection mirror, the third dual-wavelength high-reflection mirror, the harmonic output mirror, and the fourth dual-wavelength high-reflection mirror constitute a resonant cavity.

2. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The first dual-wavelength high-reflection mirror has a 0° reflection and is set perpendicular to the horizontal line; the second dual-wavelength high-reflection mirror has a 45° reflection and is set at a 45° angle to the horizontal line; the third dual-wavelength high-reflection mirror has a 45° reflection and is set at a 45° angle to the horizontal line; the harmonic output mirror is set parallel to the third dual-wavelength high-reflection mirror; and the fourth dual-wavelength high-reflection mirror has a 0° reflection and is set parallel to the horizontal line.

3. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The first dual-wavelength high-reflection mirror, the second dual-wavelength high-reflection mirror, the third dual-wavelength high-reflection mirror, and the fourth dual-wavelength high-reflection mirror are coated with a 532nm high-reflection film and a 1064nm high-reflection film.

4. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The harmonic output mirror is coated with a 532nm high-transmittance film and a 1064nm high-reflectance film.

5. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, Both the first LD side pump module and the second LD side pump module are LD side pump Nd:YAG modules.

6. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, Both the first Q-switching switch and the second Q-switching switch are acousto-optic Q-modulators, and they are placed orthogonally in the resonant cavity.

7. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The quartz rotator is a 90° quartz rotator, which forms a 0° angle with the horizontal line.

8. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The aperture is a pinhole aperture.

9. The high-efficiency all-solid-state green laser as described in claim 1, characterized in that, The frequency doubling crystal is an LBO crystal.

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