An array output continuous deep ultraviolet solid laser

Abstract

The application discloses a kind of continuous deep ultraviolet solid laser of array output, comprising: master oscillator, optical circulator component is arranged in master oscillator side, amplifier is arranged in optical circulator component side, second harmonic generation component is arranged in optical circulator component side and four harmonic generation component is arranged in second harmonic generation component side;Wherein master oscillator includes the collimating lens of pump source, collimating lens, light splitting element, focusing lens and laser crystal sequentially arranged along optical path.Pump source emitted light beam is collimated after collimating lens, and is diffracted into uniform M×N pump dot array (M and N are all integers) by light splitting element, and M×N pump dot is formed by focusing lens to pump dot array and focusing to the front surface of laser crystal, and the distance between each pump dot can be changed by changing the distance between light splitting element and focusing lens.According to the application, the M×N dot array output of long-life deep ultraviolet continuous laser with single frequency, high power and good beam quality is realized by the way of multi-beam parallel output.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a continuous deep ultraviolet solid-state laser with array output. Background Technology

[0002] Deep ultraviolet (DUV) lasers possess significant advantages such as high photon energy, high spectral resolution, and small focused spot size, making them widely used in the ultra-precision processing of various metallic and non-metallic materials without producing noticeable thermal effects. High-power UV and DUV lasers can be used for defect detection in wafer processing, silicon carbide annealing, and other applications, playing an indispensable role in semiconductor chip manufacturing. Furthermore, DUV lasers can be used to excite specific chemical reactions. Based on these advantages, DUV lasers have broad market application prospects and extremely high industrialization value.

[0003] Methods for obtaining deep ultraviolet (200 nm–350 nm) lasers include coherent radiation from free-electron lasers, nonlinear frequency conversion of excimer lasers, and semiconductor, solid-state, or fiber lasers. While free-electron and excimer lasers can produce high-performance ultraviolet lasers, the laser systems are typically large, complex, and expensive, especially when using corrosive halogen gases. Another approach utilizes frequency doubling with various nonlinear crystals (such as BBO, CLBO, KBBF) to construct continuous-wave deep ultraviolet lasers with high power (≤1 W) and good beam quality. However, the frequency conversion from near-infrared to deep ultraviolet involves high-order nonlinear processes such as fourth harmonication and optical parametric oscillators (OPOs) plus frequency doubling, thus requiring high peak power laser pulses to ensure conversion efficiency. Furthermore, the output power of continuous-wave deep ultraviolet lasers is often limited by the low power density of the fundamental frequency beam and the complexity of the entire frequency doubling system. Existing commercially available continuous-wave deep ultraviolet lasers typically operate at power levels of 0.1–1 W, with limited potential for further power increases: increasing the laser crystal length can improve the output power of a single-frequency fundamental laser, but the resulting increase in laser cavity length will further lead to multi-longitudinal-mode output; increasing the pump power can increase the power, but at high pump power, not only will it lead to multi-longitudinal-mode output of the fundamental laser, but it is also prone to damaging the frequency doubling crystal and its optical coating when frequency doubling to the ultraviolet band, thus reducing the lifespan of the deep ultraviolet laser system. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an array-output continuous deep ultraviolet solid-state laser, achieving array output of the laser beam and realizing coherent lattice output of a single-frequency, high-power, high-beam-quality, long-life deep ultraviolet continuous laser through multi-beam parallel output. To achieve the above-mentioned objectives and other advantages of the present invention, an array-output continuous deep ultraviolet solid-state laser is provided, comprising:

[0005] A main oscillator, an optical circulator assembly disposed on one side of the main oscillator, an amplifier disposed on one side of the optical circulator assembly, a second harmonic generation assembly disposed on one side of the optical circulator assembly, and a fourth harmonic generation assembly disposed on one side of the second harmonic generation assembly.

[0006] The main oscillator includes a pump source, a collimating lens, a beam splitter, a focusing lens, and a laser crystal arranged sequentially along the optical path. The pump source is a fiber-coupled laser or a laser system, and the beam splitter is a Dammann grating, a parallel plane beam splitter, or a fiber optic splitter, etc. The beam emitted by the pump source is collimated by the collimating lens and then diffracted into a uniform M×N pump array by the beam splitter. The focusing lens focuses the pump array onto the front surface of the laser crystal to form M×N pump points. The spacing between each pump point can be changed by changing the distance between the beam splitter and the focusing lens. The laser crystal is very short along the optical axis (100um~300um), and the front and rear surfaces form a flat cavity to ensure that a single longitudinal mode output of the array is obtained.

[0007] Preferably, the amplifier includes a first dichroic mirror, a second dichroic mirror, an amplifier crystal, and a first dot matrix and a second dot matrix disposed on both sides of the amplifier crystal; the first dichroic mirror and the second dichroic mirror are both tilted and the tilt angle and direction are the same; the front and rear surfaces of the first dichroic mirror and the second dichroic mirror are coated with a fundamental frequency anti-reflection film and a pump light total reflection film; the first dot matrix and the second dot matrix are symmetrically placed, including an 808nm laser pump source 9, a collimating lens 10, a beam splitter 11, and a focusing lens 12.

[0008] Preferably, the amplifier crystal is an Nd:YVO4 crystal with a length in the range of millimeters to centimeters. The front surface of the amplifier crystal is coated with pump light and fundamental frequency light anti-reflection film, and the rear surface is coated with fundamental frequency light total reflection film and pump light high transmittance film. The temperature control of the amplifier crystal is maintained within the room temperature range.

[0009] Preferably, the optical circulator assembly includes a first collimating lens, a first half-wave plate, a polarizing beam splitter, a second half-wave plate, and a second collimating lens; by rotating the first half-wave plate and the second half-wave plate, the polarization directions of the two M×N point arrays emitted from the main oscillator and the amplifier are made orthogonal; the polarizing beam splitter is used to superimpose the two beams with orthogonal polarization directions in the prism to enhance the power of the fundamental point array.

[0010] Preferably, the second harmonic generation component includes a third half-wave plate disposed on one side of the polarization beam splitter, a first focusing lens disposed on one side of the third half-wave plate, and a first frequency doubling crystal disposed on one side of the first focusing lens.

[0011] Preferably, the fourth harmonic generation component includes a second focusing lens disposed on one side of the first frequency doubling crystal and a second frequency doubling crystal disposed on one side of the second focusing lens.

[0012] Compared with the prior art, the beneficial effects of this invention are:

[0013] (1) A solid-state laser with M×N array pumped by a solid-state laser is used to realize the array output of the laser beam. Under the condition that the power intensity of a single laser beam is not high and the damage to optical thin films and nonlinear crystals is limited, a long-life deep ultraviolet continuous laser with single frequency, high power and good beam quality is realized by multi-beam parallel output.

[0014] (2) In an M×N lattice-pumped solid-state laser, the distance between the pump light lattice points in the gain medium can be adjusted. When the distance between the pump points is large, independent output from each pump point can be achieved, theoretically resulting in a total output power that is M×N times the power of a single beam. When the distance between the pump points is small, the gain regions formed by the absorption of the pump light by the laser crystal are very close, and stimulated emission interferes and couples with each other during amplification, exhibiting a stable phase relationship. This allows for coherent output from the M×N lattice, thereby significantly increasing the output laser power. Compared to a single beam, the theoretical maximum increase in total output power is (M×N). 2 times.

[0015] The focus of this invention is to obtain a deep ultraviolet laser with sufficient power. The key points are as follows: (1) utilizing a short-cavity, long-length thin-film laser oscillator to output a single-longitudinal-mode (i.e., single-frequency) infrared fundamental frequency laser in an M×N array; (2) using a long-length laser crystal to amplify the obtained single-longitudinal-mode array laser to obtain a high-power infrared array fundamental frequency light; (3) selecting a suitable nonlinear crystal to sequentially perform frequency doubling and quadruple harmonics on the array fundamental frequency light to obtain a deep ultraviolet laser. At the same time, in order to avoid damage to the coating of optical components in the laser oscillator by the high-power fundamental frequency light in the single-channel oscillator, it is necessary to appropriately adjust the spot size of the M×N lattice pump light in the laser crystal during the experiment, so as to increase the power of the single-channel fundamental frequency light without damaging the coating. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a continuous deep ultraviolet solid-state laser with array output according to the present invention;

[0017] Figure 2 A schematic diagram and working principle diagram of the Dammann grating of the continuous deep ultraviolet solid-state laser with array output according to the present invention;

[0018] Figure 3 This is a schematic diagram of the beam splitting principle of a parallel plane beam splitter for a continuous deep ultraviolet solid-state laser with array output according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Reference Figures 1-3 A continuous deep ultraviolet solid-state laser with array output includes: a master oscillator, an optical circulator assembly disposed on one side of the master oscillator, an amplifier disposed on one side of the optical circulator assembly, a second harmonic generation assembly disposed on one side of the optical circulator assembly, and a fourth harmonic generation assembly disposed on one side of the second harmonic generation assembly.

[0021] The main oscillator comprises a pump source 1, a collimating lens 2, a beam splitter 3, a focusing lens 4, and a laser crystal 5 arranged sequentially along the optical path. The pump source 1 is a fiber-coupled laser or laser system, whose output pulses feature high power, narrow linewidth, and good beam quality. The beam splitter 3 can be a Dammann grating, a parallel plane beam splitter, or a fiber optic splitter. The beam emitted from the pump source 1 is collimated by the collimating lens 2 and then diffracted into a uniform pump array by the beam splitter 3. The focusing lens 4 focuses the pump array onto the front surface of the laser crystal 5, forming an M×N pump array. The spacing between the pump points can be changed by altering the distance between the beam splitter 3 and the focusing lens 4. Using a Dammann grating as an example, the method of converting approximately parallel pump light into a diffraction field with array output is illustrated, achieving 2×2 array pumping to obtain a 2×2 deep ultraviolet array laser output. The focusing lens 4 focuses the 2×2 pump array onto the front surface of the laser crystal 5 to form four pump points. The spacing between each pump point can be changed by altering the distance between the beam splitter 3 and the focusing lens 4. When the spacing between each pump point is large, independent output of each pump point can be achieved, and theoretically, the total output power is four times that of a single beam. When the spacing between each pump point is small, the pump points interfere with each other and have a stable phase relationship, enabling coherent output of the 2×2 array, thereby significantly increasing the output laser power, which is theoretically 16 times higher than that of a single beam. The laser crystal 6 has a very short length along the optical axis, ranging from 100µm to 300µm, and its front and rear surfaces form a flat cavity to ensure a single longitudinal mode output of a 2×2 lattice. The front surface of the laser crystal 6 serves as the input mirror of the resonant cavity, and is coated with an anti-reflection film with a pump light wavelength of 808nm and a high-reflection film with a wavelength of 1064nm. The rear surface serves as the output mirror of the resonant cavity, and is coated with a total reflection film with a wavelength of 808nm and a high-reflection film with a wavelength of 1064nm. The laser crystal 6 is strictly aligned with the pump light; otherwise, the divergence angle of the output 2×2 lattice will be very large. The entire laser crystal 6 is surrounded by a copper sheet, and its temperature is maintained at room temperature to reduce thermal effects.

[0022] Optionally, the Dammann grating is a binary phase element. Its beam-splitting principle is that after the incident beam is collimated, it is split into a uniform beam of equal intensity upon striking the Dammann grating. This beam is then converged and coupled into the output fiber array by a converging lens, thus achieving the beam-splitting function. Its schematic diagram and working principle are as follows: Figure 2 As shown.

[0023] Optionally, if the parallel plane beam-splitter is used as beam-splitting element 3, its beam-splitting principle is as follows: Figure 3 a. A parallel-plane beam splitter has a semi-transparent, semi-reflective coating on its front surface. It directly reflects one half of the incident light into a new beam M1, while the other half is transmitted and emitted as beam M2. Due to two refractions and one reflection, M1 and M2 are parallel in direction. The parallel-plane beam splitter thus splits a beam into two, with the beam spacing controlled by the thickness of the beam splitter. By increasing the number of beam splitters, the process can be repeated, thereby obtaining multiple parallel beams from a single beam, such as... Figure 3 As shown in b, the beam splitter consists of two parallel plane beam splitters, which ultimately divide a beam of light into four equal beams.

[0024] Furthermore, the amplifier includes a first dichroic mirror 13-1, a second dichroic mirror 13-2, an amplifier crystal 14, and a first dot matrix and a second dot matrix disposed on both sides of the amplifier crystal 14. The first and second dot matrix devices are symmetrically placed and include an 808nm wavelength laser pump source 9, a collimating lens 10, a beam splitter 11, and a focusing lens 12. The first dichroic mirror 13-1 and the second dichroic mirror 13-2 are both tilted at 45° and in the same tilt direction. The front and rear surfaces of the first dichroic mirror 13-1 and the second dichroic mirror 13-2 are coated with a fundamental frequency anti-reflection film and a pump light total reflection film. The first dichroic mirror 13-1 is used to separate the 808nm wavelength dot matrix pump light and the 1064nm wavelength dot matrix fundamental wave; the second dichroic mirror is used to filter out the remaining 808nm wavelength dot matrix pump light. The amplifier crystal 14 is an Nd:YVO4 crystal with a length ranging from millimeters to centimeters. The front surface of the amplifier crystal 14 is coated with pump light and fundamental frequency light anti-reflection film, and the rear surface is coated with fundamental frequency light total reflection film and pump light high transmittance film. The amplifier crystal is surrounded by copper sheet and the temperature is maintained at room temperature to reduce the thermal effect in the gain crystal.

[0025] Furthermore, the optical circulator assembly includes a first collimating lens 6, a first half-wave plate 7, a polarizing beam splitter 8, a second half-wave plate 15, and a second collimating lens 16. By rotating the first half-wave plate 7 and the second half-wave plate 15, the polarization directions of the two beams emitted from the main oscillator and the amplifier are made orthogonal. The polarizing beam splitter 8 is used to superimpose the two beams with orthogonal polarization directions in the prism, thereby enhancing the power of the fundamental wave array and transmitting the fundamental wave array to the frequency doubling device.

[0026] Furthermore, the second harmonic generation component includes a third half-wave plate 17 disposed on one side of the polarization beam splitter 8, a first focusing lens 18 disposed on one side of the third half-wave plate 17, and a first frequency doubling crystal 19 disposed on one side of the first focusing lens 18. The third half-wave plate 17 can rotate the linear polarization direction of the 2×2 1064nm wavelength fundamental wave array to align with the main axis of the first frequency doubling crystal 19, achieving optimal phase matching with the SHG to maximize conversion efficiency. SHG is the abbreviation for second harmonic generation, which is a second harmonic generation. The focusing state of the first focusing lens 18 can simultaneously affect the optical power and beam quality of the SHG. That is, the smaller the 2×2 fundamental wave array spot focused into the frequency doubling crystal, the greater the SHG power, but it may lead to a decrease in beam quality, which will be detrimental to the generation of a high-quality SHG array. Therefore, the size of the focused spot can be appropriately enlarged. The first frequency doubling crystal 19 has advantages such as a high damage threshold, a relatively high nonlinear coefficient, wide bandwidth, non-critical phase matching capability, and small space walk-off effect, like a type I non-critical phase matching KTP or LBO crystal. The front and rear surfaces of the first frequency doubling crystal 19 are coated with anti-reflection films of a fundamental frequency wave with a wavelength of 1064nm and an SHG with a wavelength of 532nm. The first frequency doubling crystal 19 is mounted on a copper thermal surface and the temperature is maintained at room temperature. Its center is located at the focal point of the first focusing lens 18.

[0027] Furthermore, the fourth harmonic generation component includes a second focusing lens 20 disposed on one side of the first frequency doubling crystal 19 and a second frequency doubling crystal 21 disposed on one side of the second focusing lens 20. The second frequency doubling crystal 21 has a high nonlinear coefficient, a high laser damage threshold, and mature growth technology, such as BBO and CLBO crystals. The front and rear surfaces of the second frequency doubling crystal 21 are coated with a 266nm wavelength FHG antireflection film. FHG is the English abbreviation for fourth harmonic generation, which is the fourth harmonic. The second frequency doubling crystal 21 is mounted on a copper thermal surface, and the temperature is maintained at room temperature. The thermal surface is mounted on a five-axis adjustment bracket to allow precise control of the crystal's angle and position.

[0028] The number of devices and processing scale described herein are for the purpose of simplifying the description of the invention, and applications, modifications and variations thereof will be apparent to those skilled in the art.

[0029] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A continuous-wave deep ultraviolet solid-state laser with array output, characterized in that, include: A main oscillator, an optical circulator assembly disposed on one side of the main oscillator, an amplifier disposed on one side of the optical circulator assembly, a second harmonic generation assembly disposed on one side of the optical circulator assembly, and a fourth harmonic generation assembly disposed on one side of the second harmonic generation assembly. The master oscillator is used to generate an M×N matrix of fundamental frequency laser light, where M and N are both integers. The master oscillator includes a first pump source (1), a first collimating lens (2), a first beam splitter (3), a third focusing lens (4), and a laser crystal (5) arranged sequentially along the optical path. The pump source (1) is a fiber-coupled laser or a laser system. The first beam splitter (3) is a Damman grating, a parallel plane beam splitter, or a fiber splitter. The beam emitted by the pump source (1) is collimated by the first collimating lens (2) and then diffracted into a uniform M×N pump matrix by the first beam splitter (3). The third focusing lens (4) is used to focus the pump matrix onto the front surface of the laser crystal (5) to form M×N pump points. The spacing between each pump point can be changed by changing the distance between the first beam splitter (3) and the third focusing lens (4). The length of the laser crystal (5) along the optical axis is very short, ranging from 100 μm to 300 μm. The front and rear surfaces form a flat cavity to ensure a single longitudinal mode output of an M×N dot matrix; The optical circulator assembly includes a second collimating lens (6), a first half-wave plate (7), a polarization beam splitter (8), a second half-wave plate (15), and a third collimating lens (16). By rotating the first half-wave plate (7) and the second half-wave plate (15), the polarization directions of the two M×N point arrays emitted from the main oscillator and the amplifier are made orthogonal. The polarization beam splitter (8) is used to superimpose the two beams with mutually orthogonal polarization directions in the prism, thereby enhancing the power of the fundamental point array.

2. A continuous-wave deep ultraviolet solid-state laser with array output as described in claim 1, wherein, The amplifier includes a first dichroic mirror (13-1), a second dichroic mirror (13-2), an amplifier crystal (14), and a first dot matrix and a second dot matrix disposed on both sides of the amplifier crystal (14). The first dichroic mirror (13-1) and the second dichroic mirror (13-2) are both tilted and have the same tilt angle and direction. The front and rear surfaces of the first dichroic mirror (13-1) and the second dichroic mirror (13-2) are coated with a fundamental frequency anti-reflection film and a pump light total reflection film. The first dot matrix and the second dot matrix are placed symmetrically, including a second 808 nm laser pump source (9), a fourth collimating lens (10), a second beam splitter (11), and a fourth focusing lens (12).

3. A continuous-wave deep ultraviolet solid-state laser with array output as described in claim 1, wherein, The amplifier crystal (14) is a Nd:YVO4 crystal with a length ranging from millimeters to centimeters. The front surface of the amplifier crystal (14) is coated with pump light and fundamental frequency light anti-reflection film, and the rear surface is coated with fundamental frequency light total reflection film and pump light high transmittance film. The amplifier crystal temperature control is maintained within the room temperature range.

4. A continuous-wave deep ultraviolet solid-state laser with array output as described in claim 1, wherein, The second harmonic generation component includes a third half-wave plate (17) disposed on one side of the polarization beam splitter (8), a first focusing lens (18) disposed on one side of the third half-wave plate (17), and a first frequency doubling crystal (19) disposed on one side of the first focusing lens (18).

5. A continuous-wave deep ultraviolet solid-state laser with array output as described in claim 1, characterized in that, The fourth harmonic generation component includes a second focusing lens (20) disposed on one side of the first frequency doubling crystal (19) and a second frequency doubling crystal (21) disposed on one side of the second focusing lens (20).

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