A pulsed solid-state laser

Abstract

The present invention relates to the field of laser technology, and in particular to a pulsed solid-state laser. The pulsed solid-state laser comprises an end-pumped LD, a pump light coupling unit, a resonant cavity, and an extracavity frequency-doubling unit, arranged sequentially along the direction of light. A first reflector, a laser crystal, an acousto-optic Q-switch, a second reflector, a frequency-doubler crystal, and a third reflector form a V-shaped resonant cavity, and a second focusing mirror, a third focusing mirror, a first BBO crystal, and a second BBO crystal form the extracavity frequency-doubling unit. The present invention converts 1064nm fundamental frequency light into 532nm frequency-doubled light through intracavity frequency-doubler (IVH), then generates 266nm laser light through extracavity frequency-quadrupling (IVH), and finally separates the remaining 532nm and 266nm laser light. The overall frequency-doubler conversion efficiency is high, the optical path is flexible, and the structure is compact.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, in particular to a pulsed solid-state laser. Background Art

[0002] Deep ultraviolet lasers, characterized by high photon energy, small spot size, and high material absorption, are widely used in scientific research, military industry, and other fields. In scientific research, the ultrahigh resolution characteristics of deep ultraviolet lasers are often used to develop physical, optoelectronic, chemical, and biological materials. In the military field, ultraviolet communication technology based on deep ultraviolet lasers has demonstrated significant advantages. In industrial processing, deep ultraviolet lasers are often used for lithography, thin film microchannel processing, precision cutting, and welding.

[0003] 266nm deep ultraviolet lasers are widely used in ultra-precision machining, semiconductor wafer etching, doping and other processes, and also show great potential in technical fields such as photolithography and material surface modification. At present, 266nm all-solid-state lasers obtained through frequency doubling conversion technology have become the mainstream in the market due to their compact structure and high beam quality. High-repetition-rate 266nm lasers can be used in fields such as marking and crystal cutting, and are also commonly used for PCB board cutting. Due to the low frequency doubling conversion efficiency and the strict operating temperature requirements of the frequency doubling crystal, the laser is large in size and has high power consumption, and an innovative design optimization is still needed.

[0004] The Chinese invention patent with publication number CN112688151A uses an intracavity doubled frequency design to generate a 532nm laser, and then generates a 266nm laser through the CLBO crystal quadruple frequency effect. However, because the CLBO crystal is extremely easy to deliquesce and requires a high temperature of 140°C to operate, it has high requirements for the working environment and requires a separate high-temperature working chamber to be designed, which takes up a large space and is difficult to operate. Summary of the Invention

[0005] The object of the present invention is to provide a pulsed solid-state laser that can solve the above-mentioned technical problems.

[0006] The present invention provides a pulsed solid-state laser, comprising an end-pumped LD, a pump light coupling unit, a V-shaped resonant cavity, and an extracavity frequency doubling unit, which are sequentially arranged along a light direction; the pump light coupling unit is composed of a first collimating mirror and a first focusing mirror; the V-shaped resonant cavity is composed of a first reflecting mirror, a laser crystal, an acousto-optic Q-switch, a second reflecting mirror, a frequency doubling crystal, and a third reflecting mirror; the extracavity frequency doubling unit is composed of a second focusing mirror, a first BBO crystal, a third focusing mirror, and a second BBO crystal; the extracavity frequency doubling unit is further sequentially provided with a fifth reflecting mirror and a dichroic beam splitter on one side along the laser output direction; a fourth reflecting mirror is provided between the second focusing mirror and the first BBO crystal; the laser further comprises an isolation device consisting of a polarization beam splitter prism and a quarter-wave plate; the polarization beam splitter prism is located between the second reflecting mirror and the second focusing mirror; and the quarter-wave plate is located between the second BBO crystal and the fifth reflecting mirror.

[0007] Preferably, the end-pumped LD is a fiber-coupled semiconductor laser with a central wavelength of 808 nm.

[0008] Preferably, the first reflector is a plane mirror, the surface of which is coated with an 808nm anti-reflection film and a 1064nm high-reflection film.

[0009] Preferably, the second reflector is a plano-concave mirror, the surface of which is coated with a 1064nm high-reflection film and a 532nm anti-reflection film.

[0010] Preferably, the third reflector is a plane mirror, the surface of which is coated with 532nm and 1064nm high-reflection films.

[0011] Preferably, the laser crystal is a Nd:YVO4 crystal, the Nd ion doping concentration is 0.2at.%-0.5at.%, the crystal length is 8-15mm, it is a-axis cut, and the light-transmitting surface is coated with a 1064 / 808nm double anti-reflection film.

[0012] Preferably, the frequency doubling crystal is an LBO crystal with a crystal length of 8-15 mm, a cutting angle of 11.2°, a 1064 / 532 nm double antireflection film on the light-transmitting surface, and an operating temperature of 30°C.

[0013] Preferably, the fourth reflector is a plane mirror, the surface of which is coated with a 532nm anti-reflection film and a 266nm high-reflection film; the fifth reflector is a plane mirror, the surface of which is coated with a 532nm high-reflection film and a 266nm anti-reflection film.

[0014] Preferably, the first BBO crystal has a crystal length of 6-12 mm, a cutting angle of 47.7°, a 532 / 266 nm double anti-reflection film on the light-transmitting surface, and an operating temperature of 80°C; the second BBO crystal has a crystal length of 6-12 mm, a cutting angle of 47.7°, a 532 / 266 nm double anti-reflection film on the light-transmitting surface, and an operating temperature of 80°C.

[0015] Preferably, the length of arm I of the solid laser is 30-90 mm, and the length of arm II is 30-90 mm (arm I and arm II are as follows Figure 1 As shown), the folding angles of the arm I and the arm II are 10°-30°.

[0016] The end-pumped LD emits an 808nm pump laser which is injected into the laser crystal through the pump coupling unit, causing the laser crystal to generate a population inversion and generate a 1064nm laser through the resonant cavity. The acousto-optic Q switch is inserted into the resonant cavity to convert it into a pulsed laser. The 1064nm pulsed laser continuously oscillates between the first reflector, the second reflector, and the third reflector, and is converted into a 532nm laser in the doubled frequency crystal in the second arm of the resonant cavity. The 532nm laser is output from the second reflector, and the polarization beam splitter reflects the S polarized light to the extracavity frequency doubling unit, and enters the first BBO crystal through the second focusing mirror. The first BB The O crystal absorbs the S-polarized 532nm laser and converts part of it into 266nm laser. The second BBO crystal absorbs P-polarization. The remaining S-polarized 532nm laser passes through the second BBO crystal and passes through the 1 / 4 wave plate. The fifth reflector will reflect the remaining 532nm laser and pass through the 1 / 4 wave plate again. At this time, the S-polarized 532nm laser is converted into P polarization, passes through the second BBO crystal, is absorbed and partially converted into 266nm laser, is reflected by the fourth reflector, and is emitted through the dichroic beam splitter together with the 266nm laser generated by the first BBO crystal. The excess 532nm laser will be emitted by the polarization beam splitter prism.

[0017] Beneficial effects:

[0018] The miniaturized pulsed solid-state laser provided by the present invention converts 1064nm fundamental frequency light into 532nm frequency-doubled light by intracavity frequency doubling, and then generates 266nm laser by extracavity frequency quadrupling. The overall cavity shape of the resonant cavity is a V cavity. The two optical waists provided by the V cavity are sufficient to place the laser crystal and the frequency-doubled crystal respectively, so that the fundamental frequency light can pass through the LBO crystal to achieve multiple conversions. At the same time, it also avoids the absorption of the frequency-doubled light by the laser crystal, effectively improving the light conversion efficiency. The isolation device composed of a polarization beam splitter prism and a 1 / 4 wave plate prevents back reflection light from entering the resonant cavity, thereby improving the stability of the resonant cavity. The frequency quadrupling crystal uses BBO crystal, which has the advantages of low cost, high damage threshold, and wide matching temperature. Compared with CLBO crystal, it is simpler and more stable to use, and does not require a separate constant temperature chamber to be designed. The extracavity frequency-doubled optical path design enables the 532nm laser to pass through the BBO crystal to and fro, effectively improving the extracavity frequency-doubled conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a schematic diagram of the overall structure of Example 1 of the present invention;

[0021] Figure 2 Schematic diagram of the focusing effect of the third focusing mirror in Example 1 of the present invention.

[0022] Explanation of the reference numerals: 1-end-pumped LD, 2-first collimating mirror, 3-first focusing mirror, 4-first reflecting mirror, 5-laser crystal, 6-acousto-optic Q-switch, 7-second reflecting mirror, 8-doubled frequency crystal, 9-third reflecting mirror, 10-polarization beam splitter, 11-second focusing mirror, 12-fourth reflecting mirror, 13-first BBO crystal, 14-third focusing mirror, 15-second BBO crystal, 16-1 / 4 wave plate, 17-fifth reflecting mirror, 18-dichroic beam splitter. DETAILED DESCRIPTION

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

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Example 1

[0027] See also Figure 1 The present invention discloses a pulsed solid-state laser, comprising an end-pumped LD 1, a first collimating mirror 2, a first focusing mirror 3, a first reflecting mirror 4, a laser crystal 5, an acousto-optic Q-switch 6, a second reflecting mirror 7, a frequency doubling crystal 8, a third reflecting mirror 9, a polarization beam splitter 10, a second focusing mirror 11, a fourth reflecting mirror 12, a first BBO crystal 13, a third focusing mirror 14, a second BBO crystal 15, a quarter-wave plate 16, a fifth reflecting mirror 17, and a dichroic beam splitter 18, arranged sequentially along the light direction. The first collimating mirror 2 and the first focusing mirror 3 form a pump coupling unit, the first reflecting mirror 4, the laser crystal 5, the acousto-optic Q-switch 6, the second reflecting mirror 7, the frequency doubling crystal 8, and the third reflecting mirror 9 form a V-type resonant cavity, and the second focusing mirror 11, the fourth reflecting mirror, the first BBO crystal 13, the third focusing mirror 14, and the second BBO crystal 15 form an extracavity frequency doubling unit.

[0028] The end-pumped LD is a fiber-coupled semiconductor laser with a central wavelength of 808 nm. The first collimator 2 is a plano-convex lens with a diameter of 10.4, an R of 5.6, and an 808 nm anti-reflection coating. The first focusing lens 3 is a plano-convex lens with a diameter of 12.7, an R of 16, and an 808 nm anti-reflection coating. The first reflector 4 is a plane mirror coated with an 808 nm anti-reflection coating and a 1064 nm high-reflection coating. The second reflector 7 is a plano-concave lens coated with a 532 nm anti-reflection coating and a 1064 nm high-reflection coating. The third reflector 9 is a plano-concave lens coated with a 532 nm / 1064 nm high-reflection coating. The laser crystal 5 is an Nd:YVO4 crystal with a Nd doping concentration of 0.4 at.%, a length of 10 mm, and a light-transmitting surface coated with a 1064 nm / 808 nm double anti-reflection coating. The acousto-optic Q switch 6 is SGQ80-106 from the 26th Institute of China Electronics. The 4-1QH3-2 acousto-optic Q switch has an operating frequency of 80 MHz, a clear aperture of 1.5 mm, a diffraction efficiency greater than 80%, and a transmittance greater than 99.5%. The doubled frequency crystal 8 is an LBO crystal with a crystal length of 10 mm, a cutting angle of 11.2°, and a light-transmitting surface coated with a 1064 / 532 nm double anti-reflection coating. The second focusing mirror 11 is a plano-convex lens with a diameter of 12.7 mm and an R16 coated with a 532 nm laser anti-reflection coating. The first BBO crystal is 10 mm long and has a cutting angle of 47.7°, and a light-transmitting surface coated with a 532 / 266 nm double anti-reflection coating. The third focusing mirror 14 is a plano-convex lens with a diameter of 12.7 mm and an R32 coated with 532 nm and 266 nm laser anti-reflection coatings. The second BBO crystal is 10 mm long and has a cutting angle of 47.7°, and a light-transmitting surface coated with a 532 / 266 nm double anti-reflection coating.

[0029] In this embodiment, 1064nm fundamental frequency light is generated in the laser resonant cavity by exciting the laser crystal through the end-face pumping LD 1, and the 1064nm fundamental frequency light is converted into 532nm frequency-doubled light by the doubled frequency crystal 8. After the fundamental frequency light passes through the doubled frequency crystal 8 once, the remaining 1064nm fundamental frequency light and the 532nm frequency-doubled light after the single conversion are reflected by the third reflector 9 and pass through the doubled frequency crystal 8 again to further amplify the 532nm frequency-doubled light. The 532nm frequency-doubled light is output from the resonant cavity through the second reflector 7. The polarization beam splitter prism 10 reflects the S-polarized light to the extracavity frequency-doubled unit, and is focused by the second focusing mirror 11 into the first BBO crystal 13. The first BBO crystal 13 absorbs the S-polarized 532nm laser and converts part of it into The 266nm laser is absorbed by the second BBO crystal 15 for P polarization, and the remaining S-polarized 532nm laser passes through the second BBO crystal 15 and the 1 / 4 wave plate 16. The fifth reflector 17 reflects the S-polarized 532nm laser and changes its direction, and passes through the 1 / 4 wave plate again. At this time, the 532nm laser is converted from S polarization to P polarization, passes through the second BBO crystal, is absorbed and partially converted into 266nm laser. The 266nm laser generated by the second BBO crystal is reflected by the fourth reflector and changed in direction, and enters the dichroic beam splitter together with the 266nm laser generated by the first BBO crystal to separate the excess 532nm laser.

[0030] Among them, the polarization beam splitter prism 10 can reflect S polarized light at 90 degrees and transmit P polarized light. The isolation device composed of the polarization beam splitter prism and the 1 / 4 wave plate can prevent the returned P polarized 532nm laser from entering the resonant cavity, ensuring the stability of the resonant cavity. The focusing effect of the third focusing mirror 14 is as follows: Figure 2 As shown, the 532 nm laser reflected back by the fifth reflecting mirror 17 can be focused into the second BBO crystal 15 .

[0031] The absorption conversion efficiency of 808nm pump light to 1064nm laser light is approximately 70%, and the Q-switching efficiency is approximately 70%. The frequency-doubled conversion efficiency of 1064nm laser light to 532nm laser light is approximately 50%. During pulsed output, the conversion efficiency of 532nm laser frequency-doubled light to 266nm ultraviolet light is approximately 25%. With a pump LD output power of 30W, the output 266nm ultraviolet light power is: 30W * 70% * 70% * 50% * 25% ≈ 1.8W. The present invention provides a miniaturized 266nm pulsed solid-state laser that converts 1064nm fundamental frequency light into 532nm frequency-doubled light through intracavity frequency doubling. The fundamental frequency light's round-trip travel through the frequency-doubled crystal improves the frequency-doubled efficiency, resulting in a flexible optical path and compact structure. Furthermore, a unique extracavity frequency-doubled optical path allows the 532nm laser light to pass through the BBO crystal multiple times, improving the extracavity frequency-doubled conversion efficiency. Compared to existing 266nm solid-state lasers, the overall optical path design is simple, stable, reliable, and easily adjustable.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An extracavity quadruple frequency pulsed solid-state laser, characterized in that: The invention comprises an end-pumped LD, a pump light coupling unit, a V-type resonant cavity, and an extracavity frequency doubling unit arranged in sequence along the light direction; the pump light coupling unit comprises a first collimating mirror and a first focusing mirror; the V-type resonant cavity comprises a first reflecting mirror, a laser crystal, an acousto-optic Q-switch, a second reflecting mirror, a frequency doubling crystal, and a third reflecting mirror; the extracavity frequency doubling unit comprises a second focusing mirror, a fourth reflecting mirror, a first BBO crystal, a third focusing mirror, a second BBO crystal, a fifth reflecting mirror, and a dichroic beam splitter arranged in sequence along the laser output direction; the laser further comprises an isolation device consisting of a polarization beam splitter prism and a quarter-wave plate; the polarization beam splitter prism is located between the second reflecting mirror and the second focusing mirror, and reflects S-polarized light to the extracavity frequency doubling unit; the quarter-wave plate is located between the second BBO crystal and the fifth reflecting mirror; the first BBO crystal absorbs S-polarization, and the second BBO crystal absorbs P-polarization.

2. The pulsed solid-state laser according to claim 1, characterized in that The end-pump LD is a fiber-coupled semiconductor laser with a central wavelength of 808 nm.

3. The pulsed solid-state laser according to claim 1, characterized in that The first reflector is a plane mirror, the surface of which is coated with an 808nm anti-reflection film and a 1064nm high-reflection film.

4. The pulsed solid-state laser according to claim 1, characterized in that The second reflector is a plano-concave mirror, the surface of which is coated with a 1064nm high-reflection film and a 532nm anti-reflection film.

5. The pulsed solid-state laser according to claim 1, characterized in that The third reflector is a plane mirror, and the surface of the mirror is coated with 532nm and 1064nm high reflection films.

6. The pulsed solid-state laser according to claim 1, characterized in that The laser crystal is Nd:YVO4 crystal, the Nd ion doping concentration is 0.2at.%-0.5at.%, the crystal length is 8-15mm, a-axis cutting, and the light-transmitting surface is coated with a 1064 / 808nm double anti-reflection film.

7. The pulsed solid-state laser according to claim 1, characterized in that The double frequency crystal is an LBO crystal with a crystal length of 8-15 mm, a cutting angle of 11.2°, a 1064 / 532 nm double antireflection film on the light-transmitting surface, and an operating temperature of 30°C.

8. The pulsed solid-state laser according to claim 1, characterized in that The fourth reflector is a plane mirror, the surface of which is coated with a 532nm anti-reflection film and a 266nm high-reflection film; the fifth reflector is a plane mirror, the surface of which is coated with a 532nm high-reflection film and a 266nm anti-reflection film.

9. The pulsed solid-state laser according to claim 1, characterized in that The first BBO crystal has a crystal length of 6-12 mm, a cutting angle of 47.7°, a 532 / 266 nm double anti-reflection film on the light-transmitting surface, and an operating temperature of 80°C. The second BBO crystal has a crystal length of 6-12 mm, a cutting angle of 47.7°, a 532 / 266 nm double anti-reflection film on the light-transmitting surface, and an operating temperature of 80°C.

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