Miniaturized laser based on diode single tube pumping and MOPA structure

Abstract

The invention discloses a miniaturized laser based on diode single tube pumping and an MOPA structure, and belongs to the technical field of lasers. The laser comprises a seed source generation module, a seed source amplification module and a laser output and frequency doubling conversion module. A diode single-tube pump is combined with a plurality of groups of shaping cavity mirrors to realize high-efficiency coupling of pump light and a gain crystal, and high-quality seed light is generated through passive Q-switching. Seed light passes through the polarization two-way amplification structure, two times of energy extraction is achieved in the amplification gain crystal, and the energy utilization rate is increased. And the laser output part realizes high-efficiency frequency doubling output through a folded light path and a frequency doubling crystal. According to the invention, all optical elements and the heat dissipation substrate are tightly integrated by adopting a high-temperature curing process, so that the structural stability and the heat dissipation efficiency are effectively improved, the comprehensive optimization of the laser in the aspects of miniaturization, high-energy output and environmental adaptability is realized, and the laser is suitable for compact application scenes such as vehicle-mounted laser radars and unmanned aerial vehicle loads.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a miniaturized laser based on diode single-tube pumping and MOPA structure. Background Technology

[0002] With the rapid development of technologies in fields such as precision manufacturing, remote sensing, and medicine, there is an urgent need for lasers to have high energy, high beam quality, and miniaturization. Traditional high-energy solid-state lasers, especially those using flash lamp pumping, generally suffer from problems such as large size, low pumping efficiency, and complex heat dissipation systems, making them unsuitable for applications with extremely high requirements for equipment size and portability, such as vehicle-mounted lidar and drone payloads.

[0003] To overcome the aforementioned limitations, existing technologies mostly employ solid-state lasers with a MOPA (Master Oscillator Power Amplifier) ​​configuration. A high-quality seed beam is generated by the master oscillator, and then amplified by the power amplifier, thus balancing output energy and beam quality. In terms of pumping methods, semiconductor laser pumping has become mainstream, specifically including LD (laser diode) fiber-coupled pumping and single-tube diode pumping. However, while LD fiber-coupled pumping can achieve high power, its system requires complex fiber coupling modules (including coupling fiber, collimating lens, focusing lens, etc.), resulting in a complex overall structure and large size, and introducing additional losses during fiber transmission. In contrast, single-tube diode pumping has a simpler structure, eliminating the need for fiber transmission, and is more conducive to system miniaturization.

[0004] Furthermore, in terms of pump structure layout, end-face pumping and side-face pumping are two common methods. End-face pumping makes it easy to achieve mode matching between the pump light and the oscillating light, and has higher thermal management efficiency. On the other hand, side-face pumping tends to form a large temperature gradient inside the gain medium, resulting in significant thermal effects. It often requires a complex multi-channel water cooling system, which further increases the laser size and reduces its environmental adaptability.

[0005] Besides the optical structure, the connection and fixing process of laser components also directly affects their miniaturization and long-term stability. Traditional bolt fixing or conventional adhesive bonding methods have problems such as large component gaps, loose structure, and suboptimal heat dissipation paths. Under harsh environments such as high temperature and vibration, optical components are prone to displacement or optical path deviation, which in turn affects the performance and reliability of the laser.

[0006] Therefore, there is still a lack of a miniaturized laser solution in the existing technology that can effectively balance high energy output, excellent beam quality, compact structure and high environmental stability. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a miniaturized laser based on diode single-tube pumping and an MOPA structure. By utilizing diode single-tube pumping and combining it with a compact optical structure, end-face pumping is employed to optimize the pump layout, achieving miniaturization while improving pumping efficiency. A high-temperature curing process is used to tightly bond the core components to the heat dissipation substrate, improving heat dissipation efficiency and structural stability, and preventing component displacement and optical path offset. Through overall rational optimization of the laser structure, stable laser performance is ensured under complex environments.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A miniaturized laser based on diode single-tube pumping and MOPA structure includes a seed source generation module, a seed source amplification module, and a laser output and frequency doubling conversion module arranged sequentially along the optical path; wherein...

[0010] The seed source generation module includes a first diode single-tube pump module, a first optical shaping system, and a resonant cavity composed of a rod-shaped gain crystal, a passive Q-switching module, and a seed source output cavity mirror. The first optical shaping system shapes the pump light emitted by the first diode single-tube pump module into a symmetrical light spot that matches the end face of the rod-shaped gain crystal, and outputs seed source pulse light based on the resonant cavity.

[0011] The seed source amplification module includes a second diode single-tube pump module, a second optical shaping system, and a polarization double-pass amplification structure composed of a thin-film polarizer, a λ / 4 waveplate, and an amplification gain crystal, so that the seed source pulse light completes two energy extractions in the amplification gain crystal to obtain high-energy laser.

[0012] The laser output and frequency doubling module is used to output the high-energy laser.

[0013] Furthermore, all optical components of the laser are fixed on the same substrate through a high-temperature curing process, forming an integrated and compact structure.

[0014] Furthermore, both the first and second optical shaping systems include multiple shaping cavities for performing fast-axis compression focusing and slow-axis beam expansion collimation on the pump light emitted from the first and second diode single-tube pump sources, respectively, to form symmetrical light spots that match the end face size of the corresponding gain crystal.

[0015] Furthermore, in the seed source generation module, the first pump light emitted by the first diode single-tube pump module is sequentially injected into the rod-shaped gain crystal through the first shaping cavity mirror, the second shaping cavity mirror, and the third shaping cavity mirror. The end face of the rod-shaped gain crystal near the pump source acts as the front cavity mirror, and together with the rod-shaped gain crystal, the passive Q-switching module, and the seed source output cavity mirror, they form a stable resonant cavity. In the resonant cavity, the first pump light is continuously injected into the rod-shaped gain crystal to generate population inversion. The passive Q-switching module realizes the periodic accumulation and release of energy in the resonant cavity through its saturable absorption characteristics, and finally outputs the seed source pulse light through the seed source output cavity mirror.

[0016] Furthermore, in the seed source amplification module, the second pump light emitted by the second diode single-tube pump module passes sequentially through the seventh, sixth, and fifth shaping cavity mirrors and is incident on the amplification gain crystal, generating population inversion. The seed source pulse light passes through a thin-film polarizer and becomes linearly polarized light, then passes through a λ / 4 waveplate and is converted into circularly polarized light. It then enters the amplification gain crystal and interacts with the inverted particles within the crystal through stimulated emission, achieving the first energy amplification. After the first energy amplification, the laser light is reflected by the front end of the amplification gain crystal and returns along the original path to the thin-film polarizer, where it is inverted into circularly polarized light. The inverted circularly polarized light then passes through the λ / 4 waveplate again and is converted back into linearly polarized light with the polarization direction orthogonal to the initial incident direction. It then passes through the amplification gain crystal again, achieving efficient energy amplification once more.

[0017] Furthermore, the end faces of the rod-shaped gain crystal and the amplification gain crystal near the corresponding pump source are coated with a dielectric film that is highly transparent to the pump light wavelength and highly reflective to the seed source pulse light wavelength.

[0018] Furthermore, the seed source pulse output from the seed source output cavity mirror is collimated by the fourth shaping cavity mirror. After collimation, the seed source pulse light passes through the first and second reflecting mirrors in sequence to change its propagation direction and is accurately incident on the thin film polarizer.

[0019] Furthermore, the thin-film polarizer has polarization selectivity, reflecting s-polarized light while transmitting p-polarized light.

[0020] Furthermore, in the laser output and frequency doubling conversion module, the high-energy laser is collimated using the eighth and ninth shaping cavity mirrors and then output through the frequency doubling crystal.

[0021] Furthermore, the high-energy laser reaches the third reflecting mirror via the eighth shaping cavity mirror, and after a 45° reflection deflection, the optical path is folded. The deflected laser then reaches the ninth shaping cavity mirror, which collimates and shapes the beam. After being transmitted through the output cavity mirror, it sequentially enters the second-harmonic crystal and the third-harmonic crystal, achieving efficient output of the frequency-doubled laser.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention simplifies the fiber coupling module through single-tube diode pumping and optimizes the pump optical path using end-face pumping, reducing pump system space and improving coupling efficiency between the pump light and the crystal. It achieves a high-efficiency balance between small size and high energy using the MOPA structure. The invention utilizes a high-temperature curing process to ensure tight bonding between the crystal, pump source, MOPA core components, and heat dissipation substrate, eliminating component gaps. Compared to bolt fixing or conventional adhesives, which are prone to component displacement and optical path misalignment, leading to unstable performance in complex environments, the high-temperature curing process not only improves heat dissipation efficiency and enhances the overall structural strength but also effectively prevents component displacement and optical path misalignment under complex environments with wide temperature ranges and vibration, significantly improving long-term operational stability. Attached Figure Description

[0024] Figure 1 This is a structural diagram of a miniaturized laser based on diode single-tube pumping and MOPA structure according to the present invention.

[0025] Figure label:

[0026] 1. First diode single-tube pump module; 2. First shaping cavity mirror; 3. Second shaping cavity mirror; 4. Third shaping cavity mirror; 5. Rod-shaped gain crystal; 6. Passive Q-switching module; 7. Seed source output cavity mirror; 8. Fourth shaping cavity mirror; 10. First reflector; 11. Second reflector; 12. Thin-film polarizer; 13. λ / 4 waveplate; 14. Amplification gain crystal; 15. Fifth shaping cavity mirror; 16. Sixth shaping cavity mirror; 17. Seventh shaping cavity mirror; 18. Second diode single-tube pump module; 19. Eighth shaping cavity mirror; 20. Third reflector; 21. Ninth shaping cavity mirror; 22. Output cavity mirror; 23. Second harmonic crystal; 24. Third harmonic crystal. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] This invention proposes a miniaturized laser based on a diode-driven single-tube pump and a MOPA structure. First, by optimizing the structural integration through a high-temperature curing process, it further overcomes the bottlenecks in laser miniaturization and weight reduction. Addressing the issue of excessive size in traditional lasers due to loose connections between components and complex heat dissipation structures, the high-temperature curing process for the diode-driven single-tube pump chip, the core components of the MOPA structure, and the heat dissipation substrate achieves a gapless, tight fit between components, reducing the space required for traditional screw fixing or conventional bonding. This makes it more suitable for miniaturized applications such as automotive LiDAR. Second, based on miniaturization, the MOPA structure leverages the amplification advantages of combining a master oscillator and amplifier, combined with the advantages of diode-driven single-tube pumping, enabling the laser to output high-beam-quality, high-peak-power pulsed lasers, meeting the requirements of LiDAR, high-precision machining, and other applications. Finally, the high-temperature curing process enhances the structural reliability, improving the laser's stability and environmental adaptability, ensuring long-term reliable operation.

[0029] like Figure 1 As shown, this invention discloses a miniaturized laser based on diode single-tube pumping and a MOPA structure, comprising a seed source generation module, a seed source amplification module, and a laser output and frequency doubling conversion module arranged sequentially along the optical path. All components in the module are mounted on the same plane and arranged sequentially according to the optical path transmission order; their order cannot be changed. All components are cured using a high-temperature process to ensure the stability of each element. Specifically:

[0030] In the seed source generation module, the first diode single-tube pump module 1 serves as the pump source. The emitted pump light needs to undergo precise optical shaping to achieve efficient coupling with the rod-shaped gain crystal 5. The first pump light is injected into the rod-shaped gain crystal 5 sequentially through the first shaping cavity mirror 2, the second shaping cavity mirror 3, and the third shaping cavity mirror 4. Due to the inherent characteristics of the single diode, the size and divergence angle of the emitted first pump light along the fast and slow axes differ. The fast axis divergence angle is larger and the spot size is smaller, while the slow axis divergence angle is smaller but the spot size is larger. If this spatial asymmetry is not corrected, it will lead to uneven energy distribution of the pump light within the rod-shaped gain crystal 5, reducing pumping efficiency. Therefore, the first shaping cavity mirror 2, the second shaping cavity mirror 3, and the third shaping cavity mirror 4 are used in conjunction to compress and focus the light along the fast axis and expand and collimate it along the slow axis. This shapes the first pump spot into a symmetrical spot that matches the size and mode of the end face of the rod-shaped gain crystal 5, thereby achieving uniform distribution of the pump light within the gain medium, improving absorption efficiency, and providing a stable energy basis for subsequent laser oscillation and amplification. The end face of the rod-shaped gain crystal 5 closest to the pump source undergoes a special coating treatment. This end face is coated with a high-transmittance film for the wavelength of the first pump light, ensuring that the first pump light emitted by the first diode single-tube pump module 1 can be efficiently injected into the rod-shaped gain crystal 5. At the same time, this end face is also coated with a high-reflectance film for the laser wavelength generated by the rod-shaped gain crystal 5, enabling it to act as a front cavity mirror. Therefore, the end face of the rod-shaped gain crystal 5 closest to the pump source acts as a front cavity mirror, forming a stable resonant cavity together with the rod-shaped gain crystal 5, the passive Q-switching module 6, and the seed source output cavity mirror 7. Within the resonant cavity, the first pump light is continuously injected into the rod-shaped gain crystal 5, generating population inversion. The passive Q-switching module 6 utilizes its saturable absorption characteristics to achieve periodic energy accumulation and release within the resonant cavity, ultimately outputting a high-beam-quality seed source pulse light through the seed source output cavity mirror 7. This structural design significantly reduces the size of the seed source, while the high-temperature curing process ensures the stability of each component, providing a high-beam-quality and stable seed source for subsequent amplification stages.

[0031] In the seed source amplification module, polarization two-way amplification technology is used to further enhance the energy of the seed source. The seed source pulse light output from the seed source output cavity mirror 7 undergoes long-distance transmission, inevitably resulting in beam expansion. Therefore, a fourth shaping cavity mirror 8 is used to collimate and adjust the laser beam. After collimation, the seed source pulse light passes sequentially through the first reflecting mirror 10 and the second reflecting mirror 11 to change its propagation direction and precisely enter the thin-film polarizer 12, which is then injected into the amplification system. The first reflecting mirror 10 and the second reflecting mirror 11 can optionally be placed in orthogonal positions. The thin-film polarizer 12 has polarization selectivity characteristics, reflecting s-polarized light and transmitting p-polarized light. Meanwhile, the second pump light emitted by the second diode single-tube pump module 18 is processed by an optical shaping system composed of the seventh shaping cavity mirror 17, the sixth shaping cavity mirror 16, and the fifth shaping cavity mirror 15. The pump light is compressed and focused in the fast axis direction and expanded and collimated in the slow axis direction, ultimately shaping the pump light spot into a symmetrical spot that matches the end face size and mode volume of the amplification and gain crystal 14, so as to ensure efficient coupling of pump energy. Similar to the rod-shaped gain crystal 5, the end surface of the amplification and gain crystal 14 near the second diode single-tube pump module 18 is specially coated. This end face is coated with a high-transmittance film for the pump light wavelength, which ensures that the second pump light emitted by the second diode single-tube pump module 18 can be efficiently injected into the amplification and gain crystal 14 to produce population inversion. At the same time, this end face is coated with a high-reflectance film for the seed source pulse light wavelength, so that it can act as a front cavity mirror. The seed source pulse light passes through the thin-film polarizer 12, becoming linearly polarized. Then, after passing through the λ / 4 waveplate 13, the linearly polarized light is converted to circularly polarized light and enters the amplification and gain crystal 14. There, it interacts with the inverted particles within the crystal through stimulated emission, achieving the first energy amplification. The amplified laser light is reflected from the front face of the amplification and gain crystal 14, reversing its propagation direction and synchronously reversing its polarization rotation (e.g., left-handed circularly polarized light becomes right-handed circularly polarized light), returning along the original path. The inverted circularly polarized light passes through the λ / 4 waveplate 13 again, reverting to linearly polarized light with a polarization direction orthogonal to the initial incident direction (p-polarized light becomes s-polarized light). It then passes through the amplification and gain crystal 14 again, achieving a second, highly efficient energy amplification, doubling the energy utilization rate. Through this polarization-based two-way amplification mechanism, the seed source pulse light completes two energy extractions within the same amplification and gain crystal 14, significantly improving energy utilization and ultimately achieving high-energy output while effectively simplifying the system structure.

[0032] In the laser output and frequency doubling module, the seed source pulse light is amplified by polarization double-pass and output as a high-energy laser from the thin-film polarizer 12. After traveling a certain distance, beam divergence inevitably occurs. If not corrected, the subsequent frequency-second and frequency-third harmonic crystals 23 and 24 will be unable to effectively receive and utilize the energy, reducing the frequency doubling efficiency. Therefore, the eighth shaping cavity mirror 19 and the ninth shaping cavity mirror 21 are used to collimate the laser. Specifically, the high-energy laser output from the thin-film polarizer 12 first enters the eighth shaping cavity mirror 19, reaches the third reflecting mirror 20, and undergoes a 45° reflection deflection to achieve spatial folding of the optical path. The deflected laser then enters the ninth shaping cavity mirror 21. The ninth shaping cavity mirror 21 and the eighth shaping cavity mirror 19 work together to collimate and shape the beam to ensure that the laser spot matches the end face size and mode volume of the frequency-second and frequency-third harmonic crystals 23 and 24, thereby improving energy utilization efficiency. The laser, controlled by the ninth shaping cavity mirror 21, ultimately reaches the output cavity mirror 22. The fundamental frequency laser transmitted through the output cavity mirror 22 then sequentially enters the second-harmonic crystal 23 and the third-harmonic crystal 24. Because the fundamental frequency laser is controlled in the early stages, a uniform optical field distribution is formed in the frequency-harmonic crystals, satisfying the nonlinear optical phase-matching condition, ultimately achieving efficient output of the frequency-harmonic laser. The entire output process employs a folded optical path design, further compressing the laser system size and meeting the miniaturization design requirements of miniaturized lasers.

[0033] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A miniaturized laser based on diode single-tube pumping and MOPA structure, characterized in that, It includes a seed source generation module, a seed source amplification module, and a laser output and frequency doubling conversion module arranged sequentially along the optical path; among which, The seed source generation module includes a first diode single-tube pump module, a first optical shaping system, and a resonant cavity composed of a rod-shaped gain crystal, a passive Q-switching module, and a seed source output cavity mirror. The first optical shaping system shapes the pump light emitted by the first diode single-tube pump module into a symmetrical light spot that matches the end face of the rod-shaped gain crystal, and outputs seed source pulse light based on the resonant cavity. The seed source amplification module includes a second diode single-tube pump module, a second optical shaping system, and a polarization double-pass amplification structure composed of a thin-film polarizer, a λ / 4 waveplate, and an amplification gain crystal, so that the seed source pulse light completes two energy extractions in the amplification gain crystal to obtain high-energy laser. The laser output and frequency doubling module is used to output the high-energy laser. All optical components of the laser are fixed on the same substrate through a high-temperature curing process, forming an integrated and compact structure.

2. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 1, characterized in that, Both the first and second optical shaping systems include multiple shaping cavities.

3. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 2, characterized in that, The first optical shaping system and the second optical shaping system include multiple shaping cavities, which are used to perform fast-axis compression focusing and slow-axis beam expansion collimation on the pump light emitted by the first diode single-tube pump module and the second diode single-tube pump module, respectively, to form a symmetrical light spot that matches the end face size of the corresponding gain crystal.

4. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 3, characterized in that, In the seed source generation module, the first pump light emitted by the first diode single-tube pump module is injected into the rod-shaped gain crystal through the first shaping cavity mirror, the second shaping cavity mirror, and the third shaping cavity mirror in sequence. The end face of the rod-shaped gain crystal near the pump source acts as the front cavity mirror, and together with the rod-shaped gain crystal, the passive Q-switching module, and the seed source output cavity mirror, they form a stable resonant cavity. In the resonant cavity, the first pump light is continuously injected into the rod-shaped gain crystal to generate population inversion. The passive Q-switching module realizes the periodic accumulation and release of energy in the resonant cavity through its saturable absorption characteristics, and finally outputs the seed source pulse light through the seed source output cavity mirror.

5. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 4, characterized in that, In the seed source amplification module, the second pump light emitted by the second diode single-tube pump module passes sequentially through the seventh, sixth, and fifth shaping cavity mirrors and is incident on the amplification gain crystal, resulting in population inversion. The seed source pulse light passes through a thin-film polarizer and becomes linearly polarized, then passes through a λ / 4 waveplate and is converted into circularly polarized light. It then enters the amplification gain crystal and interacts with the inverted particles within the crystal through stimulated emission, achieving the first energy amplification. After the first energy amplification, the laser light is reflected by the front end of the amplification gain crystal and returns along the original path to the thin-film polarizer, where it is inverted into circularly polarized light. The inverted circularly polarized light passes through the λ / 4 waveplate again and is converted back into linearly polarized light with the polarization direction orthogonal to the initial incident direction. It then passes through the amplification gain crystal again, achieving efficient energy amplification once more.

6. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 5, characterized in that, The end faces of the rod-shaped gain crystal and the amplification gain crystal near the corresponding pump source are coated with a dielectric film that is highly transparent to the pump light wavelength and highly reflective to the seed source pulse light wavelength.

7. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 6, characterized in that, The seed source pulse output from the seed source output cavity mirror is collimated by the fourth shaping cavity mirror. After collimation, the seed source pulse light passes through the first and second reflecting mirrors in sequence to change its propagation direction and is accurately incident on the thin film polarizer.

8. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 7, characterized in that, The thin-film polarizer has polarization selectivity, reflecting s-polarized light and transmitting p-polarized light.

9. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 1, characterized in that, In the laser output and frequency doubling conversion module, the high-energy laser is collimated using the eighth and ninth shaping cavity mirrors and then output through the frequency doubling crystal.

10. A miniaturized laser based on diode single-tube pumping and MOPA structure according to claim 9, characterized in that, The high-energy laser beam reaches the third reflecting mirror via the eighth shaping cavity mirror. After being deflected by 45°, the optical path is folded. The deflected laser beam then reaches the ninth shaping cavity mirror, which collimates and shapes the beam. After being transmitted through the output cavity mirror, the beam enters the second-harmonic crystal and the third-harmonic crystal in sequence, achieving efficient output of the frequency-doubled laser.

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