A miniaturized laser based on diode single-pump and MOPA structure

Abstract

The application discloses a kind of miniaturization laser based on diode single tube pumping and MOPA structure, belong to laser technical field.The laser includes seed source generation module, seed source amplification module and laser output and frequency doubling conversion module.Adopt diode single tube pumping to combine multiple groups of shaping cavity mirror to realize the efficient coupling of pump light and gain crystal, and high-quality seed light is generated by passive Q switching.Seed light is amplified by polarization double-pass amplification structure, and twice energy extraction is realized in amplification gain crystal, to improve energy utilization.Laser output part realizes efficient frequency doubling output by folding light path and frequency doubling crystal.The application adopts high-temperature curing process to tightly integrate each optical element and heat dissipation substrate, effectively improves the structural stability and heat dissipation efficiency, realizes the comprehensive optimization of laser in miniaturization, high energy output and environmental adaptability, and is suitable for compact application scenarios such as vehicle-mounted laser radar, unmanned aerial vehicle load, etc.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lasers, and particularly relates to a miniaturized laser based on diode single-tube pumping and a MOPA structure. BACKGROUND

[0002] With the rapid development of technologies in the fields of precision manufacturing, remote sensing detection and medical treatment, there is an urgent need for lasers with large energy, high beam quality and miniaturization. Traditional large-energy solid-state lasers, especially those using flash lamp pumping, generally have problems such as large size, low pumping efficiency and complex heat dissipation system, and are difficult to adapt to application scenarios such as vehicle-mounted laser radar and unmanned aerial vehicle load, which have extremely high requirements for the size and portability of equipment.

[0003] To overcome the above limitations, solid-state lasers with a MOPA (Master Oscillator Power Amplifier) configuration are commonly used in the prior art. The high-quality seed light is generated by a master oscillator, and then the energy is amplified by a power amplifier, so as to balance the output energy and beam quality. In terms of pumping mode, semiconductor laser pumping has become the mainstream, including LD (laser diode) fiber-coupled pumping and diode single-tube pumping. However, the LD fiber-coupled pumping scheme can achieve relatively high power, but the system needs to be equipped with a complex fiber coupling module (including coupling fibers, collimating mirrors, focusing mirrors, etc.), resulting in a complex overall structure, a large size, and additional losses in the fiber transmission process. In contrast, the diode single-tube pumping structure is simpler and does not require fiber transmission, which is more conducive to system miniaturization.

[0004] In addition, in terms of pumping structure layout, end-pumping and side-pumping are two common ways. End-pumping is easy to achieve mode matching between pumping light and oscillation light, and has high thermal management efficiency. Side-pumping, on the other hand, tends to form a large temperature gradient inside the gain medium, resulting in significant thermal effects, and often requires a complex multi-channel water cooling system, further increasing the size of the laser and reducing environmental adaptability.

[0005] In addition to the optical structure, the connection and fixing process of the laser assembly also directly affects its miniaturization and long-term stability. Traditional bolt fixing or conventional adhesive bonding methods have problems such as large gaps between components, loose structure, and suboptimal heat dissipation path, which can easily cause displacement or optical path deviation of optical elements in harsh environments such as high temperature and vibration, thereby affecting the performance and reliability of the laser.

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

[0007] To solve the above technical problems, the application provides a miniaturized laser based on diode single tube pumping and MOPA structure, which realizes miniaturization and improves pumping efficiency by utilizing diode single tube pumping, combining a compact optical structure, and optimizing the pumping layout by end-pumping.

[0008] To achieve the above object, the application adopts the following technical scheme:

[0009] A miniaturized laser based on diode single tube pumping and MOPA structure, comprising a seed source generation module, a seed source amplification module and a laser output and frequency conversion module arranged along an optical path in sequence; wherein,

[0010] The seed source generation module comprises a first diode single tube pumping 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 pumping module into a symmetric spot matched with 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 comprises a second diode single tube pumping module, a second optical shaping system and a polarization double-pass amplification structure composed of a thin film polarizer, a lambda / 4 wave plate and an amplification gain crystal, so that the seed source pulse light completes twice energy extraction in the amplification gain crystal to obtain high-energy laser;

[0012] The laser output and frequency conversion module is used for outputting the high-energy laser.

[0013] Further, all optical elements of the laser are fixed on the same substrate by a high-temperature curing process to form an integrated compact structure.

[0014] Further, the first optical shaping system and the second optical shaping system each comprise a plurality of shaping cavity mirrors for respectively compressing and focusing the pump light emitted by the first diode single tube pumping source and the second diode single tube pumping source in the fast-axis direction and expanding and collimating the pump light in the slow-axis direction to form a symmetric spot matched with the size of the corresponding gain crystal end face.

[0015] Further, in the seed source generation module, the first pump light emitted by the first diode single-tube pump module sequentially passes through the first shaping cavity mirror, the second shaping cavity mirror and the third shaping cavity mirror and is injected into the rod-shaped gain crystal, the end face of the rod-shaped gain crystal close to the pump source is coated with a cavity mirror, and the rod-shaped gain crystal, the passive Q-switching module and the seed source output cavity mirror jointly form a stable resonant cavity, in the resonant cavity, the first pump light continuously injects into the rod-shaped gain crystal to generate particle inversion, the passive Q-switching module realizes periodic accumulation and release of energy in the resonant cavity through the saturable absorption characteristic, and finally the seed source pulse light is output through the seed source output cavity mirror.

[0016] Further, in the seed source generation module, the first pump light emitted by the first diode single-tube pump module sequentially passes through the first shaping cavity mirror, the second shaping cavity mirror and the third shaping cavity mirror and is injected into the rod-shaped gain crystal, the end face of the rod-shaped gain crystal close to the pump source is coated with a cavity mirror, and the rod-shaped gain crystal, the passive Q-switching module and the seed source output cavity mirror jointly form a stable resonant cavity, in the resonant cavity, the first pump light continuously injects into the rod-shaped gain crystal to generate particle inversion, the passive Q-switching module realizes periodic accumulation and release of energy in the resonant cavity through the saturable absorption characteristic, and finally the seed source pulse light is output through the seed source output cavity mirror.

[0017] Further, the end face of the rod-shaped gain crystal and the end face of the amplification gain crystal close to the corresponding pump source are coated with a dielectric film which has high transmission to the pump light wavelength and high reflection to the seed source pulse light wavelength.

[0018] Further, the seed source pulse output from the seed source output cavity mirror is collimated through the fourth shaping cavity mirror, and the collimated seed source pulse light is sequentially reflected by the first reflector and the second reflector to accurately enter the thin film polarizer.

[0019] Further, the thin film polarizer has polarization selection characteristics, reflects s-polarized light and transmits p-polarized light.

[0020] Further, in the laser output and frequency doubling conversion module, the eighth shaping cavity mirror and the ninth shaping cavity mirror are used to collimate the large-energy laser and output the large-energy laser through the frequency doubling crystal.

[0021] Further, the large-energy laser reaches the third reflector through the eighth shaping cavity mirror, is reflected and deflected by 45° to realize spatial folding of the optical path, and the deflected laser is incident on the ninth shaping cavity mirror to collimate and shape the light beam, is transmitted through the output cavity mirror, and sequentially enters the second frequency doubling crystal and the third frequency doubling crystal to realize efficient output of the frequency-doubled laser.

[0022] The application has the beneficial effects that:

[0023] The application simplifies the fiber coupling module by the diode single tube pumping, optimizes the pumping light path by the end face pumping, reduces the pumping system space, improves the coupling efficiency of the pumping light and the crystal, realizes the small size and large energy high efficiency balance by the MOPA structure, and realizes the close adhesion of the crystal, the pumping source, the MOPA core element and the heat dissipation substrate by the high temperature curing process, eliminates the gap between the components, compared with the bolt fixation or the conventional adhesive, the problems such as element displacement and light path deviation are easy to occur, the performance is unstable in the complex environment, the high temperature curing process not only improves the heat dissipation efficiency and enhances the strength of the overall structure, but also can effectively prevent the element displacement and the light path deviation in the wide temperature, vibration and other complex environments, and effectively improves the long-term working stability. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A small-sized laser structure based on diode single tube pumping and MOPA structure.

[0025] Reference signs:

[0026] The first diode single tube pumping module 1, the first shaping cavity mirror 2, the second shaping cavity mirror 3, the third shaping cavity mirror 4, the rod-shaped gain crystal 5, the passive Q-switching module 6, the seed source output cavity mirror 7, the fourth shaping cavity mirror 8, the first reflecting mirror 10, the second reflecting mirror 11, the thin film polarizer 12, the λ / 4 wave plate 13, the amplification gain crystal 14, the fifth shaping cavity mirror 15, the sixth shaping cavity mirror 16, the seventh shaping cavity mirror 17, the second diode single tube pumping module 18, the eighth shaping cavity mirror 19, the third reflecting mirror 20, the ninth shaping cavity mirror 21, the output cavity mirror 22, the second doubling crystal 23, and the third doubling crystal 24. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with the drawings and examples.

[0028] The application provides a miniaturized laser based on a diode single-tube pumping and a MOPA structure. Firstly, the structure is integrated based on a high-temperature curing process, and the bottleneck of miniaturization and light weight of the laser is further broken. For the problem of the large volume of the traditional laser caused by the loose connection of various components, the high-temperature curing treatment is performed on the diode single-tube pumping chip, the core element of the MOPA structure and the heat dissipation substrate, so that the components are closely attached without gap, and the space required by the traditional screw fixing or conventional adhesion is reduced. In this way, the laser can be more suitable for small-sized scenes such as vehicle-mounted laser radar. Secondly, on the basis of miniaturization, the MOPA structure is adopted, the amplification advantages of the master oscillator and the amplifier are combined, and the advantages of the diode single-tube pumping are combined, so that the laser can output pulsed laser with high beam quality and high peak power, and meet the requirements of laser radar, high-precision machining and the like. Finally, the stability and environmental adaptability of the laser are improved through the reliability of the high-temperature curing process structure, and long-term reliable work is ensured.

[0029] As shown in Figure 1 The application provides a miniaturized laser based on a diode single-tube pumping and a MOPA structure. Firstly, the structure is integrated based on a high-temperature curing process, and the bottleneck of miniaturization and light weight of the laser is further broken. For the problem of the large volume of the traditional laser caused by the loose connection of various components, the high-temperature curing treatment is performed on the diode single-tube pumping chip, the core element of the MOPA structure and the heat dissipation substrate, so that the components are closely attached without gap, and the space required by the traditional screw fixing or conventional adhesion is reduced. In this way, the laser can be more suitable for small-sized scenes such as vehicle-mounted laser radar. Secondly, on the basis of miniaturization, the MOPA structure is adopted, the amplification advantages of the master oscillator and the amplifier are combined, and the advantages of the diode single-tube pumping are combined, so that the laser can output pulsed laser with high beam quality and high peak power, and meet the requirements of laser radar, high-precision machining and the like. Finally, the stability and environmental adaptability of the laser are improved through the reliability of the high-temperature curing process structure, and long-term reliable work is ensured.

[0030] In the seed source generation module, the first diode single-tube pumping module 1 serves as a pumping source, and the emitted first pumping light needs to be precisely optically shaped to achieve efficient coupling with the rod-shaped gain crystal 5. The first pumping light successively passes through the first shaping cavity mirror 2, the second shaping cavity mirror 3, and the third shaping cavity mirror 4 and is injected into the rod-shaped gain crystal 5. Due to the inherent characteristics of the diode single tube, there are some differences in the fast and slow axis spot size and divergence angle of the first pumping light emitted by the diode single tube. The fast axis has a larger divergence angle and a smaller spot size, and the slow axis has a smaller divergence angle but a larger size. This spatial distribution asymmetry, if not corrected, will lead to uneven energy distribution of the pumping light in the rod-shaped gain crystal 5, reducing the pumping efficiency. Therefore, the first shaping cavity mirror 2, the second shaping cavity mirror 3, and the third shaping cavity mirror 4 are used to compress and focus in the fast axis direction, and expand and collimate in the slow axis direction, so as to shape the first pumping light spot into a symmetrical spot matching the size of the end face of the rod-shaped gain crystal 5 and the mode, thereby achieving uniform distribution of the pumping light in the gain medium, improving the absorption efficiency, and providing a stable energy basis for subsequent laser oscillation and amplification. The rod-shaped gain crystal 5 has a special coating treatment on the surface close to the pumping source. The end face is coated with a high-transmission film for the first pumping light wavelength, which ensures that the first pumping light emitted by the first diode single-tube pumping module 1 can be efficiently injected into the rod-shaped gain crystal 5. At the same time, the end face is also coated with a high-reflection film for the laser wavelength generated by the rod-shaped gain crystal 5, so that it can serve as a front cavity mirror. Therefore, the end face of the rod-shaped gain crystal 5 close to the pumping source serves as a front cavity mirror, and together with the rod-shaped gain crystal 5, the passive Q-switching module 6, and the seed source output cavity mirror 7, it forms a stable resonant cavity. In this resonant cavity, the first pumping light continuously injects into the rod-shaped gain crystal 5 to generate particle number inversion, and the passive Q-switching module 6 realizes periodic accumulation and release of energy in the resonant cavity through the saturable absorption characteristic, and finally outputs high-brightness seed source pulse light through the seed source output cavity mirror 7. This structure design greatly reduces the volume of the seed source, and the high-temperature curing process ensures the stability of each element, providing a high-brightness and stable seed source for subsequent amplification stages.

[0031] In the seed source amplification module, the polarization double-pass amplification technology is used to further improve the energy of the seed source. The seed source pulse light output from the seed source output mirror 7 is transmitted over a long distance, and the beam will inevitably be expanded. Therefore, the fourth shaping mirror 8 is used to regulate and collimate the laser. The collimated seed source pulse light successively passes through the first mirror 10 and the second mirror 11 to change the propagation direction and accurately injects into the thin film polarizer 12, and then injects into the amplification system. The first mirror 10 and the second mirror 11 are optionally placed in an orthogonal position. The thin film polarizer 12 has polarization selection characteristics, and reflects s-polarized light and transmits p-polarized light. At the same time, the second pump light emitted by the second diode single tube pumping module 18 is processed by the optical shaping system composed of the seventh shaping mirror 17, the sixth shaping mirror 16 and the fifth shaping mirror 15 to compress and focus the pump light in the fast axis direction and expand and collimate the pump light in the slow axis direction. Finally, the pump light spot is shaped into a symmetric spot matching the size of the end surface of the amplification gain crystal 14 and the mode volume, so as to ensure efficient coupling of the pump energy. Similar to the rod-shaped gain crystal 5, the amplification gain crystal 14 is specially coated on one end surface of the second diode single tube pumping module 18. The end surface is coated with a high-transmission film for the pump light wavelength, which ensures that the second pump light emitted by the second diode single tube pumping module 18 can be efficiently injected into the amplification gain crystal 14 to produce particle inversion. At the same time, the end surface is coated with a high-reflection film for the seed source pulse light wavelength, so that it can charge the front cavity mirror. The seed source pulse light passes through the thin film polarizer 12 and becomes linearly polarized light, and then passes through the λ / 4 wave plate 13 and converts the linearly polarized light into circularly polarized light, which enters the amplification gain crystal 14 and interacts with the inverted particles in the amplification gain crystal 14 to realize the first energy amplification. The amplified laser is reflected at the front end surface of the amplification gain crystal 14, the propagation direction is reversed, the polarization rotation direction is reversed (such as left-handed circularly polarized light becomes right-handed circularly polarized light), and returns along the original path. The reversed circularly polarized light passes through the λ / 4 wave plate 13 again and is converted into linearly polarized light again, and the polarization direction is orthogonal to the initial incident polarization direction. The p-polarized light is converted into s-polarized light, and then passes through the amplification gain crystal 14 again to realize efficient energy amplification again, and the energy utilization rate is doubled. Through this polarization double-pass amplification mechanism, the seed source pulse light completes two energy extractions in the same amplification gain crystal 14, the energy utilization rate is significantly improved, and finally high-energy output is realized while effectively simplifying the system structure.

[0032] In the laser output and frequency doubling conversion module, the seed source pulse light is outputted from the film polarizer 12 as high-energy laser after polarization double-pass amplification. The beam divergence inevitably occurs during a distance transmission, which will lead to the fact that the subsequent second frequency doubling crystal 23 and third frequency doubling crystal 24 cannot effectively receive and utilize the energy, thereby reducing the frequency doubling efficiency. Therefore, the eighth shaping mirror 19 and the ninth shaping mirror 21 are used to collimate the laser. The specific transmission path is that the high-energy laser outputted from the film polarizer 12 is first incident to the eighth shaping mirror 19 to reach the third mirror 20 to achieve spatial folding of the optical path through 45° reflection deflection, and the deflected laser is incident to the ninth shaping mirror 21. The ninth shaping mirror 21 and the eighth shaping mirror 19 are cooperatively controlled to collimate and shape the beam to ensure that the laser spot is matched with the end face size and mode volume of the second frequency doubling crystal 23 and the third frequency doubling crystal 24, thereby improving the energy utilization efficiency. The laser controlled by the ninth shaping mirror 21 finally reaches the output mirror 22, and then the fundamental frequency laser transmitted through the output mirror 22 enters the second frequency doubling crystal 23 and the third frequency doubling crystal 24 in turn. Since the fundamental frequency laser is controlled in advance to form a uniform light field distribution in the frequency doubling crystal, the nonlinear optical phase matching condition is met, and finally the efficient output of the frequency doubled laser is realized. The entire output process adopts the folded optical path design, further compresses the volume of the laser system, and meets the miniaturization design requirements of the small-sized laser.

[0033] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

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. The 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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