Nanosecond ultraviolet laser packaged by semiconductor laser diode in optical cavity

Abstract

The invention relates to the technical field of lasers, and discloses a nanosecond ultraviolet laser packaged by a semiconductor laser diode in an optical cavity. Comprising an optical cavity, a first plano-convex mirror, a gain medium, a Q-switched device, a second plano-convex mirror, a frequency doubling crystal, a frequency tripling crystal and a reflector. A plurality of semiconductor laser diodes, a micro-lens array and an optical fiber are arranged in the optical cavity. According to the nanosecond ultraviolet laser packaged by the semiconductor laser diode in the optical cavity, through the semiconductor laser diode packaging structure in the optical cavity and the design of the resonant cavity, the pumping efficiency of the laser is improved, high-power ultraviolet light output is further achieved, and meanwhile the stability and the structural compactness of the laser are improved.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode. Background Technology

[0002] Currently, traditional ultraviolet lasers have certain limitations in terms of power output, stability, and structural compactness. As the performance requirements for ultraviolet lasers in related applications continue to increase, developing an ultraviolet laser that can guarantee high power output while possessing better stability and a compact structure is of significant practical importance.

[0003] In fields such as precision machining, biomedicine, and aerospace, the trend towards equipment integration and miniaturization is becoming increasingly significant. For example, in the biomedical field, portable laser diagnostic and treatment equipment requires compact lasers for easy carrying and operation; in the aerospace field, the size and weight of equipment are subject to extremely strict limitations, and traditional bulky lasers are insufficient to meet these requirements. Therefore, how to reduce the size of lasers while ensuring their performance is a pressing issue that needs to be addressed. Summary of the Invention

[0004] The present invention aims to improve at least one technical problem in the prior art.

[0005] This invention provides a nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode, comprising an optical cavity, a first plano-convex mirror, a gain medium, a Q-switching device, a second plano-convex mirror, a second-harmonic crystal, a third-harmonic crystal, and a reflector; The optical cavity contains multiple semiconductor laser diodes, a microlens array, and an optical fiber. The semiconductor laser diodes are used to emit pump light, which passes sequentially through the microlens array and the optical fiber. The microlens array is used to collimate the pump light emitted by all the semiconductor laser diodes, and the optical fiber is used to couple all the pump light passing through the microlens array. Along the optical path of the pump light coupled through the optical fiber, a first plano-convex mirror, a gain medium, a Q-switching device, a second plano-convex mirror, a second-harmonic crystal, a third-harmonic crystal, and a reflector are sequentially arranged. The first plano-convex mirror has high transmittance for the pump light emitted by the semiconductor laser diode and high reflectivity for the fundamental frequency light. The second plano-convex mirror has high reflectivity for both the fundamental frequency light and the harmonic light. The pump light coupled through the optical fiber passes through the first plano-convex mirror, the gain medium, the Q-switching device, and the second plano-convex mirror to output fundamental frequency light in the form of nanosecond pulses. The fundamental frequency light passes through the second-harmonic crystal, the third-harmonic crystal, and the reflector to generate ultraviolet light.

[0006] As a further improvement to the above technical solution, the output wavelength of the semiconductor laser diode is 878nm.

[0007] As a further improvement to the above technical solution, the radius of curvature of the first plano-convex mirror is 300mm, and the radius of curvature of the second plano-convex mirror is 500mm.

[0008] As a further improvement to the above technical solution, the nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode further includes a green light absorption tube, which is disposed in the optical path of the ultraviolet light and is used to absorb the green light in the ultraviolet light.

[0009] As a further improvement to the above technical solution, the Q-switching device includes an acousto-optic Q-switching device with an operating frequency of 40kHz.

[0010] As a further improvement to the above technical solution, the second harmonic crystal is a KTP crystal, and the third harmonic crystal is an LBO crystal.

[0011] As a further improvement to the above technical solution, a resonant cavity is formed between the first plano-convex mirror and the second plano-convex mirror, and the cavity length of the resonant cavity is 115mm-125mm.

[0012] The beneficial effects of this invention are as follows: This invention provides a nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode. The optical cavity contains multiple semiconductor laser diodes, a microlens array, and an optical fiber. The pump light emitted by the semiconductor laser diodes passes sequentially through the microlens array and the optical fiber. The microlens array is used to collimate the pump light, and the optical fiber is used to couple the pump light. Along the optical path of the pump light coupled through the optical fiber, a first plano-convex mirror, a gain medium, a Q-switching device, a second plano-convex mirror, a second-harmonic crystal, a third-harmonic crystal, and a reflector are arranged sequentially. Through the in-cavity semiconductor laser diode packaging structure and the resonant cavity design, the pump efficiency of the laser is improved, thereby achieving high-power ultraviolet light output, while also improving the stability and structural compactness of the laser. Attached Figure Description

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of a nanosecond ultraviolet laser with an in-cavity semiconductor laser diode packaged according to the present invention. Figure 2 This is a schematic diagram of the structure inside the optical cavity of the present invention.

[0014] In the attached diagram: 1-Semiconductor laser diode; 2-Microlens array; 3-Fiber optic cable; 4-First plano-convex mirror; 5-Gain medium; 6-Q-switching device; 7-Second plano-convex mirror; 8-Frequency second harmonic crystal; 9-Frequency third harmonic crystal; 10-Reflector; 11-Green light absorption tube. Detailed Implementation

[0015] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0016] The following is combined Figures 1 to 2 Embodiments of the present invention will be described.

[0017] Reference Figure 1 and Figure 2 This embodiment relates to a nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode, including an optical cavity, a first plano-convex mirror 4, a gain medium 5, a Q-switching device 6, a second plano-convex mirror 7, a second-harmonic crystal 8, a third-harmonic crystal 9, and a reflector 10. The optical cavity is provided with multiple semiconductor laser diodes 1, microlens array 2, and optical fiber 3. The semiconductor laser diodes 1 are used to emit pump light. The pump light passes through the microlens array 2 and the optical fiber 3 in sequence. The microlens array 2 is used to collimate the pump light emitted by all the semiconductor laser diodes. The optical fiber 3 is used to couple all the pump light passing through the microlens array 2. Along the optical path of the pump light coupled through fiber 3, the first plano-convex mirror 4, the gain medium 5, the Q-switching device 6, the second plano-convex mirror 7, the second harmonic crystal 8, the third harmonic crystal 9, and the reflector 10 are arranged sequentially. The first plano-convex mirror 4 has high transmittance for the pump light emitted by the semiconductor laser diode 1 and high reflectivity for the fundamental frequency light. The second plano-convex mirror 7 has high reflectivity for both the fundamental frequency light and the harmonic light. The pump light coupled through fiber 3 passes through the first plano-convex mirror 4, the gain medium 5, the Q-switching device 6, and the second plano-convex mirror 7, and outputs fundamental frequency light in the form of nanosecond pulses. The fundamental frequency light passes through the second harmonic crystal 8, the third harmonic crystal 9, and the reflector 10 to generate ultraviolet light.

[0018] In this embodiment, a nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode is provided. By using the in-cavity semiconductor laser diode packaging structure and resonant cavity design, the pump efficiency of the laser is improved, thereby achieving high-power ultraviolet light output, while also improving the stability and structural compactness of the laser.

[0019] Specifically, multiple semiconductor laser diodes 1 are fixedly installed inside the optical cavity, for example, arranged in a line. A microlens array 2 is positioned at the emitting end of each semiconductor laser diode 1 to collimate and shape the pump light emitted by each diode. The emitting end of the microlens array 2 is aligned and connected to the incident end of an optical fiber 3, allowing the collimated pump light to couple into the fiber 3. The emitting end of the fiber 3 is located at the emitting end of the optical cavity. Along the propagation direction of the pump light coupled through the fiber 3, a first plano-convex mirror 4, a gain medium 5, a Q-switching device, a second plano-convex mirror 7, a second harmonic crystal 8, a third harmonic crystal 9, and a reflector 10 are sequentially arranged. The first plano-convex mirror 4 has high transmittance for the pump light and high reflectivity for the fundamental frequency light, allowing the pump light to enter the optical cavity and be absorbed by the gain medium 5, while simultaneously reflecting the fundamental frequency light generated within the cavity at one end. The gain medium 5 is installed after the first plano-convex mirror 4. After the pump light enters the gain medium 5, it excites stimulated emission, forming the fundamental frequency light. A Q-switching device 6 is positioned after the gain medium 5 to periodically modulate the cavity loss, achieving pulsed output of the fundamental frequency light. A second plano-convex mirror 7 is positioned after the Q-switching device; it has high reflectivity for both the fundamental and harmonic light, and together with the first plano-convex mirror 4, forms a stable resonant cavity. A second harmonic crystal 8 and a third harmonic crystal 9 are sequentially positioned after the second plano-convex mirror 7. The fundamental frequency light passes through the second harmonic crystal 8 to generate second harmonic light, and then the fundamental and harmonic light undergo a summation interaction in the third harmonic crystal 9 to generate ultraviolet light. A reflector 10 is positioned after the third harmonic crystal 9. The gain medium can be a neodymium-doped yttrium vanadate crystal with a neodymium ion doping concentration of 0.25 at%. Using a low-doping concentration neodymium-doped yttrium vanadate crystal can effectively reduce the thermal lensing effect, improve the beam quality within the cavity, and facilitate stable nanosecond pulse output at high repetition frequencies.

[0020] In some embodiments, the output wavelength of the semiconductor laser diode 1 is 878nm. Using an 878nm wavelength semiconductor laser diode as the semiconductor laser diode 1 results in a high degree of matching with the absorption peak of the neodymium-doped gain medium 5, which can significantly reduce quantum defects, reduce thermal effects, and improve conversion efficiency and long-term stability of the laser.

[0021] In some embodiments, the radius of curvature of the first plano-convex mirror 4 is 300 mm, and the radius of curvature of the second plano-convex mirror 7 is 500 mm. In this embodiment, by reasonably setting the radii of curvature of the first plano-convex mirror 4 and the second plano-convex mirror 7, the spot matching between the gain medium 5 and the frequency doubling crystal is improved, thereby enhancing the stability of laser output and the frequency conversion efficiency.

[0022] Reference Figure 1In some embodiments, the nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode further includes a green light absorption cylinder 11. The green light absorption cylinder 11 is disposed in the optical path of the ultraviolet light and is used to absorb the green light in the ultraviolet light. In this embodiment, by providing the green light absorption cylinder 11, the green light component mixed in the output ultraviolet light can be effectively removed, improving the spectral purity of the ultraviolet laser and avoiding interference from green light in subsequent processing or applications. Specifically, the green light absorption cylinder 11 can be made of a crystal material doped with specific ions, such as erbium-doped phosphate glass, which has a significant absorption peak in the green light band (500-600 nm) and an extremely small absorption coefficient in the ultraviolet band (200-400 nm).

[0023] In some embodiments, the Q-switching device includes an acousto-optic Q-switching device with an operating frequency of 40 kHz. In this embodiment, the use of an acousto-optic Q-switching device with an operating frequency of 40 kHz can achieve a high repetition rate output while ensuring pulse energy, making it suitable for applications such as precision machining.

[0024] In some embodiments, the second harmonic crystal 8 is a KTP crystal, and the third harmonic crystal 9 is an LBO crystal. In this embodiment, the combination of KTP and LBO crystals for frequency doubling and third harmonic conversion has the advantages of high nonlinear coefficient, high damage threshold, and good temperature stability, which can improve the output efficiency and reliability of ultraviolet laser.

[0025] Reference Figure 1 In some embodiments, a resonant cavity is formed between the first plano-convex mirror 4 and the second plano-convex mirror 7, and the cavity length of the resonant cavity is 115mm-125mm. In this embodiment, the cavity length of the resonant cavity is preferably 115mm-125mm, which is beneficial for obtaining stable fundamental frequency optical oscillation.

[0026] The preferred embodiments of the present invention have been described in detail above, but the present disclosure is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of the present disclosure.

[0027] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0028] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

Claims

1. A nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode, characterized in that, It includes an optical cavity, a first plano-convex mirror (4), a gain medium (5), a Q-switching device (6), a second plano-convex mirror (7), a second harmonic crystal (8), a third harmonic crystal (9), and a reflector (10). The optical cavity is provided with multiple semiconductor laser diodes (1), a microlens array (2), and an optical fiber (3). The semiconductor laser diodes (1) are used to emit pump light. The pump light passes through the microlens array (2) and the optical fiber (3) in sequence. The microlens array (2) is used to collimate the pump light emitted by all the semiconductor laser diodes. The optical fiber (3) is used to couple all the pump light passing through the microlens array (2). Along the optical path of the pump light coupled through the optical fiber (3), the first plano-convex mirror (4), the gain medium (5), the Q-switching device (6), the second plano-convex mirror (7), the second harmonic crystal (8), the third harmonic crystal (9), and the reflector (10) are arranged in sequence. The first plano-convex mirror (4) has high transmittance for the pump light emitted by the semiconductor laser diode (1) and high reflectivity for the fundamental frequency light. The second plano-convex mirror (7) has high reflectivity for both the fundamental frequency light and the harmonic light. The pump light coupled through the optical fiber (3) passes through the first plano-convex mirror (4), the gain medium (5), the Q-switching device (6), and the second plano-convex mirror (7) to output the fundamental frequency light in the form of nanosecond pulses. The fundamental frequency light passes through the second harmonic crystal (8), the third harmonic crystal (9), and the reflector (10) to generate ultraviolet light.

2. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: The output wavelength of the semiconductor laser diode (1) is 878nm.

3. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: The first plano-convex mirror (4) has a radius of curvature of 300 mm, and the second plano-convex mirror (7) has a radius of curvature of 500 mm.

4. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode also includes a green light absorption tube (11), which is disposed in the optical path of the ultraviolet light and is used to absorb the green light in the ultraviolet light.

5. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: The Q-switching device includes an acousto-optic Q-switching device with an operating frequency of 40 kHz.

6. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: The second harmonic crystal (8) is a KTP crystal, and the third harmonic crystal (9) is an LBO crystal.

7. The nanosecond ultraviolet laser packaged with an in-cavity semiconductor laser diode according to claim 1, characterized in that: A resonant cavity is formed between the first plano-convex mirror (4) and the second plano-convex mirror (7), and the cavity length of the resonant cavity is 115mm-125mm.

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