Pulse solid laser

Abstract

The invention relates to the technical field of lasers, in particular to a pulse solid laser which comprises an end face pumping LD, a pumping light coupling unit, a resonant cavity and an out-of-cavity frequency doubling unit which are sequentially arranged in the light direction. The first reflecting mirror, the laser crystal, the acousto-optic Q switch, the second reflecting mirror, the frequency doubling crystal and the third reflecting mirror form a V-shaped resonant cavity, and the second focusing mirror, the third focusing mirror, the first BBO crystal and the second BBO crystal form an extra-cavity frequency doubling unit. The 1064nm fundamental frequency light is converted into the 532nm frequency doubling light in an intracavity frequency doubling mode, then the 266nm laser is generated in an extracavity quadruplicated frequency mode, finally, the remaining 532nm laser and the remaining 266nm laser are separated, the overall frequency doubling conversion efficiency is high, light path adjustment is flexible, and the structure is compact.

Description

Technical Field

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

[0002] Deep ultraviolet lasers have the characteristics of high photon energy, small spot size, and high material absorption rate, and are widely used in scientific research, military, and industrial fields. In the field of scientific research, the ultra-high resolution characteristics of deep ultraviolet lasers are often used for the development of physical, optoelectronic, chemical, and biological materials; in the military field, ultraviolet communication technology based on deep ultraviolet lasers has shown great superiority; 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 processes such as ultra-precision machining, semiconductor wafer etching, and doping, and also show great potential in technical fields such as lithography technology and material surface modification. At present, the 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 applied 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 working temperature requirements of the frequency doubling crystal, the lasers are large in volume and high in power consumption, and an innovative design is still needed for optimization.

[0004] In the Chinese invention patent with the publication number CN112688151A, intracavity frequency doubling design is adopted to generate 532nm laser, and then 266nm laser is generated through the quadrupling frequency effect of the CLBO crystal. However, since the CLBO crystal is extremely easy to deliquesce and needs to work at a high temperature of 140°C, the requirements for the working environment are relatively high, and a high-temperature working chamber needs to be designed separately, which occupies a large space and is difficult to operate. Summary of the Invention

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

[0006] The present invention provides a pulsed solid-state laser, which includes an end-pumped LD, a pump light coupling unit, a V-shaped resonator, and an extracavity frequency doubling unit arranged in sequence along the light direction; the pump light coupling unit consists of a first collimating mirror and a first focusing mirror, the V-shaped resonator consists of a first reflecting mirror, a laser crystal, an acousto-optic Q-switch, a second reflecting mirror, a second harmonic generation crystal, and a third reflecting mirror, the extracavity frequency doubling unit consists of a second focusing mirror, a first BBO crystal, a third focusing mirror, and a second BBO crystal, a fifth reflecting mirror and a dichroic beam splitter are sequentially arranged on one side of the extracavity frequency doubling unit along the laser output direction, a fourth reflecting mirror is arranged between the second focusing mirror and the first BBO crystal, the laser further includes an isolation device composed of a polarization beam splitter prism and a 1 / 4 wave plate, the polarization beam splitter prism is located between the second reflecting mirror and the second focusing mirror, and the 1 / 4 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 reflecting mirror is a plane mirror, and its surface is coated with an antireflection film at 808 nm and a high reflection film at 1064 nm.

[0009] Preferably, the second reflecting mirror is a plano-concave mirror, and its surface is coated with a high reflection film at 1064 nm and an antireflection film at 532 nm.

[0010] Preferably, the third reflecting mirror is a plane mirror, and its surface is coated with high reflection films at 532 nm and 1064 nm.

[0011] Preferably, the laser crystal is a Nd:YVO 4 crystal, the doping concentration of Nd ions is 0.2 at.% - 0.5 at.%, the crystal length is 8 - 15 mm, cut along the a-axis, and the light-transmitting surface is coated with a double antireflection film at 1064 / 808 nm.

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

[0013] Preferably, the fourth reflecting mirror is a plane mirror, and its surface is coated with an antireflection film at 532 nm and a high reflection film at 266 nm; the fifth reflecting mirror is a plane mirror, and its surface is coated with a high reflection film at 532 nm and an antireflection film at 266 nm.

[0014] Preferably, for the first BBO crystal, the crystal length is 6 - 12 mm, the cutting angle is 47.7°, the light-passing surface is coated with a 532 / 266 nm double anti-reflection film, and the operating temperature is 80°C; for the second BBO crystal, the crystal length is 6 - 12 mm, the cutting angle is 47.7°, the light-passing surface is coated with a 532 / 266 nm double anti-reflection film, and the operating temperature is 80°C.

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

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

[0017] Beneficial effects:

[0018] The miniaturized pulsed solid-state laser provided by the present invention converts the 1064 nm fundamental frequency light into 532 nm second harmonic light through intracavity second harmonic generation, and then generates 266 nm laser through extracavity fourth harmonic generation. The overall cavity shape of the resonant cavity is a V cavity. The two optical waists provided by the V cavity are respectively placed with a laser crystal and a second harmonic crystal, so that the fundamental frequency light can pass through the LBO crystal back and forth to achieve multiple conversions. At the same time, the absorption of the second harmonic light by the laser crystal is avoided, effectively improving the optical conversion efficiency. The isolation device composed of a polarization beam splitter prism and a quarter-wave plate prevents the reflected light from entering the resonant cavity and improves the stability of the resonant cavity. The fourth harmonic crystal is selected as a BBO crystal, which has the advantages of low cost, high damage threshold, wide matching temperature, etc. Compared with the CLBO crystal, it is more convenient and stable to use, and there is no need to design a separate constant temperature chamber. The extracavity second harmonic optical path design enables the 532 nm laser to pass through the BBO crystal back and forth, effectively improving the extracavity second harmonic conversion efficiency. 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 will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

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

[0021] Figure 2 It is a schematic diagram of the focusing effect of the third focusing mirror in Embodiment 1 of the present invention.

[0022] Description 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 - second harmonic crystal, 9 - third reflecting mirror, 10 - polarization beam splitter prism, 11 - second focusing mirror, 12 - fourth reflecting mirror, 13 - first BBO crystal, 14 - third focusing mirror, 15 - second BBO crystal, 16 - quarter-wave plate, 17 - fifth reflecting mirror, 18 - dichroic beam splitter. Detailed Embodiments

[0023] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is 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 thus should not be construed as a limitation to the present invention.

[0025] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "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 "a plurality of" is two or more, unless otherwise specifically defined. In addition, the terms "mounted", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside 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] Embodiment 1

[0027] See Figure 1 , the present invention discloses a pulsed solid-state laser, which includes 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 second harmonic generation crystal 8, a third reflecting mirror 9, a polarization beam splitter prism 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 1 / 4 wave plate 16, a fifth reflecting mirror 17, and a dichroic beam splitter 18 arranged in sequence along the light path. 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 second harmonic generation crystal 8, and the third reflecting mirror 9 form a V-shaped resonant cavity. 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 collimating mirror 2 is a plano-convex lens with a diameter of φ10.4, a radius of curvature of R5.6, and an antireflection coating for 808 nm. The first focusing mirror 3 is a plano-convex lens with a diameter of φ12.7, a radius of curvature of R16, and an antireflection coating for 808 nm. The first reflecting mirror 4 is a plane mirror with an antireflection coating for 808 nm and a high reflection coating for 1064 nm. The second reflecting mirror 7 is a plano-concave lens with an antireflection coating for 532 nm and a high reflection coating for 1064 nm. The third reflecting mirror 9 is a plano-concave lens with a high reflection coating for 532 nm / 1064 nm. The laser crystal 5 is a Nd:YVO crystal with an Nd doping concentration of 0.4 at.%, a length of 10 mm, and a double antireflection coating for 1064 / 808 nm on the light-passing surface. 4 The acousto-optic Q-switch 6 is an acousto-optic Q-switch of the SGQ80-1064-1QH3-2 type produced by the 26th Research Institute of China Electronics Technology Corporation, with an operating frequency of 80 MHz, a light-passing aperture of 1.5 mm, a diffraction efficiency > 80%, and a transmittance > 99.5%. The second harmonic generation crystal 8 is an LBO crystal with a length of 10 mm, a cutting angle of 11.2°, and a double antireflection coating for 1064 / 532 nm on the light-passing surface. The second focusing mirror 11 is a plano-convex lens with a diameter of φ12.7, a radius of curvature of R16, and an antireflection coating for 532 nm laser. The first BBO crystal has a length of 10 mm, a cutting angle of 47.7°, and a double antireflection coating for 532 / 266 nm on the light-passing surface. The third focusing mirror 14 is a plano-convex lens with a diameter of φ12.7, a radius of curvature of R32, and antireflection coatings for 532 nm and 266 nm laser. The second BBO crystal has a length of 10 mm, a cutting angle of 47.7°, and a double antireflection coating for 532 / 266 nm on the light-passing surface.

[0029] In this embodiment, the 1064 nm fundamental frequency light is generated by exciting a laser crystal through an end-pumped LD 1 in a laser resonator. The 1064 nm fundamental frequency light is converted into 532 nm second harmonic light by a second harmonic generation crystal 8. The remaining 1064 nm fundamental frequency light after the fundamental frequency light passes through the second harmonic generation crystal 8 once and the 532 nm second harmonic light after single conversion are reflected by a third mirror 9 and then pass through the second harmonic generation crystal 8 again to further amplify the 532 nm second harmonic light. The 532 nm second harmonic light is output from the resonator through a second mirror 7. The polarization beam splitter prism 10 reflects the S-polarized light to an external cavity second harmonic generation unit, and is focused by a second focusing mirror 11 and enters a first BBO crystal 13. The first BBO crystal 13 absorbs the 532 nm S-polarized laser and partially converts it into 266 nm laser. The second BBO crystal 15 absorbs the P-polarization. The remaining 532 nm S-polarized laser passes through the second BBO crystal 15 and a quarter-wave plate 16. The fifth mirror 17 reflects the 532 nm S-polarized laser to change its direction and passes through the quarter-wave plate again. At this time, the 532 nm laser is converted from S-polarization to P-polarization, passes through the second BBO crystal, is absorbed and partially converted into 266 nm laser. The 266 nm laser generated by the second BBO crystal is reflected by a fourth mirror to change its direction and enters a dichroic beam splitter together with the 266 nm laser generated by the first BBO crystal to separate the excess 532 nm laser.

[0030] Among them, the polarization beam splitter prism 10 can reflect the S-polarized light at 90 degrees and transmit the P-polarized light. The isolation device composed of the polarization beam splitter prism and the quarter-wave plate can prevent the returned P-polarized 532 nm laser from entering the resonator to ensure the stability of the resonator. The focusing effect of the third focusing mirror 14 is as Figure 2 shown and can focus the 532 nm laser reflected back by the fifth mirror 17 into the second BBO crystal 15.

[0031] The absorption conversion efficiency from 808 nm pump light to 1064 nm laser is about 70%, and the Q-switching efficiency is about 70%; the second harmonic conversion efficiency from 1064 nm laser to 532 nm laser is about 50%; when pulsed output, the conversion efficiency of the 532 nm laser to 266 nm ultraviolet light by second harmonic generation is about 25%; the output power of the pump LD is 30 W, and the output power of the 266 nm ultraviolet light is: 30 W * 70% * 70% * 50% * 25% ≈ 1.8 W. A miniaturized 266 nm pulsed solid-state laser provided by the present invention converts 1064 nm fundamental frequency light into 532 nm second harmonic light through intracavity second harmonic generation. At the same time, the fundamental frequency light traveling back and forth through the second harmonic generation crystal can improve the second harmonic conversion efficiency, the optical path adjustment is flexible, and the structure is compact. In addition, the special extracavity second harmonic generation optical path enables the 532 nm laser to pass through the BBO crystal multiple times, improving the extracavity second harmonic conversion efficiency. Compared with the existing 266 nm solid-state lasers, the overall optical path design is simple, stable, reliable, and easy to adjust.

[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 foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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. A pulsed solid-state laser, characterized in that: The invention comprises an end-pump LD, a pump light coupling unit, a V-type resonant cavity, and an extracavity frequency doubling unit which are sequentially arranged along the direction of light; the pump light coupling unit is composed of a first collimating mirror and a first focusing mirror, the V-type resonant cavity is composed of a first reflecting mirror, a laser crystal, an acousto-optic Q switch, a second reflecting mirror, a double frequency 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 also 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 composed 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.

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, and the surface of the mirror 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, and the surface of the reflector 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 plated with a 1064 / 808nm double anti-reflection film.

7. The pulsed solid-state laser according to claim 1, characterized in that: 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 anti-reflection 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, and a 532nm anti-reflection film and a 266nm high-reflection film are coated on the surface; the fifth reflector is a plane mirror, and a 532nm high-reflection film and a 266nm anti-reflection film are coated on the surface.

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

10. The pulsed solid-state laser according to claim 1, characterized in that: The length of arm I of the solid laser is 30-90 mm, the length of arm II is 30-90 mm, and the folding angle of arm I and arm II is 10°-30°.

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