A compact laser amplification system based on spatial multiplexing structure

Abstract

This invention discloses a compact laser amplification system based on a spatial multiplexing structure. The system includes: a seed laser for providing seed signal light; a beam expander for expanding the signal light; a beam shaping device for controlling the size, spot shape, and intensity distribution of the signal light; a power amplifier system for amplifying the signal light; and a beam transmission encoding device for changing the transmission direction or polarization state of the signal light to encode and derive the number of amplifications, which, in conjunction with the power amplifier system, enables the signal light to be amplified and transmitted back and forth in the gain medium. This compact laser amplification system based on a spatial multiplexing structure achieves efficient extraction of pump energy within a small space through spatial multiplexing of the gain medium, providing a reliable technical path for miniaturized lasers.

Description

Technical Field

[0001] This invention belongs to the field of lasers, and specifically relates to a compact laser amplification system based on a spatial multiplexing structure. Background Technology

[0002] Lasers possess many unique advantages, such as readily achievable high energy and power densities, excellent directivity, and ease of long-distance transmission, playing an increasingly important role in numerous fields, including lidar, material modification, and laser processing. A multitude of potential applications require laser sources to possess both high single-pulse energy and high average power (repetition rate), while simultaneously maintaining a small size to meet user requirements for effectiveness, efficiency, and environmental adaptability. In laser design, size, energy, power, beam quality, and environmental adaptability are interdependent. Achieving high-energy, high-average-power, and high-beam-quality laser output within a small, compact space is one of the most challenging problems currently facing research on high-repetition-rate, high-average-power lasers.

[0003] Traditional high-average-power pulsed lasers typically employ a multi-stage amplification method using multiple laser media. Considering the pumping and cooling systems used in conjunction with these, there is not much room for reduction in size and weight. For example, the Mercury system, a reported joule-level pulsed laser from the United States, uses Yb:S-FAP media and outputs 60J / 10Hz / 15ns of laser light; the LUCIA system from France uses Yb:YAG gain media and outputs 14J / 2Hz / 10ns of laser light; the HALNA system from Japan uses Nd:glass gain media and has system specifications of 21J / 10Hz / 8.9ns; and the DiPOLE-HiLASE system from the UK / Czech Republic uses Yb:YAG gain media and has system specifications of 105J / 10Hz / 10ns. These high-average-power pulsed laser systems were achieved without considering size and weight costs. They are over ten meters long and weigh tens of tons or more, with complex system structures, demanding operating environments, and complex operation and maintenance.

[0004] Therefore, to achieve the miniaturization of lasers that simultaneously possess high average power and high pulse energy, it is necessary to break through the traditional amplification mode of existing high-energy lasers and realize high-gain amplification and efficient energy extraction of laser pulses in a compact space. Summary of the Invention

[0005] In view of this, the present invention proposes a compact laser amplification system based on a spatial multiplexing structure. This system enables the signal light to travel back and forth between gain media through a beam transmission encoding device. By spatially multiplexing the gain media, efficient extraction of pump energy is achieved with a small volume and weight.

[0006] To achieve this objective, the present invention adopts the following technical solution: a compact laser amplification system based on a spatial multiplexing structure, the laser amplification system comprising: a seed source laser, a beam expander, a power amplifier system, and a beam transmission encoding device;

[0007] The seed source laser outputs signal light;

[0008] The beam expander is installed on the signal light path to expand the signal light beam;

[0009] The power amplifier system includes two sheet-like gain media located in the middle layer, and a cooling medium, an isolation plate, and a laser pumping device arranged sequentially on the outside of the two gain media.

[0010] The surfaces of the two gain media that are in contact with the cooling media are coated with a high-reflectivity film for signal light and a high-transmittance film for pump light, and the surfaces of the two gain media that are opposite to each other are coated with a high-transmittance film for signal light and a high-reflectivity film for pump light.

[0011] Both surfaces of the isolation plate are coated with a pump light high-transmittance film.

[0012] The beam transmission encoding device works in conjunction with the power amplifier system to guide the signal light into the gain medium of the power amplifier system and change the transmission direction and polarization state of the signal light, so that the signal light is amplified in multiple stages between the two gain media of the power amplifier system. In the last stage of amplification, the beam transmission encoding device changes the direction of travel of the signal light so that its direction of travel is orthogonal to the direction of travel of the signal light in the previous stage of amplification.

[0013] Preferably, the center wavelength of the signal light output by the seed source laser matches the emission spectrum of the gain medium, and the energy, time waveform, and spectral distribution of the signal light output by the seed source laser can be selected according to requirements.

[0014] Preferably, the laser amplification system further includes at least one beam expander, which is disposed in the signal amplification optical path.

[0015] Preferably, the beam expander performs one or more stages of beam expansion on the signal light.

[0016] Preferably, the signal light is amplified in multiple stages between the two gain media of the power amplifier system, with each stage being either single-pass amplification or multi-pass amplification.

[0017] Preferably, the laser amplification system further includes a shaping device, which is disposed on the signal light path.

[0018] Preferably, the laser pumping device is a laser diode array, and a pump light collimation device is provided between the laser diode array and the isolation plate, or no such device is provided.

[0019] Preferably, the collimation device includes, but is not limited to, optical fibers, microlens arrays, cylindrical lenses, and conical light tubes.

[0020] Preferably, the beam transmission encoding device is any one or a combination of any number of mirrors, retroreflectors, encoding prisms, Faraday isolators, and polarizing beam splitters.

[0021] Preferably, the combination of the reflector or the Faraday isolator and the polarizing beam splitter is arranged in the optical path between different amplification stages of the signal light.

[0022] The beneficial effects of this invention are as follows: The compact laser amplification system based on spatial multiplexing structure disclosed in this invention utilizes a power amplifier system and a beam transmission encoding device to realize the round-trip transmission and amplification of signal light in the gain medium. By spatially multiplexing the gain medium, efficient extraction of pump energy is achieved in a small space, providing a reliable technical path for miniaturized lasers. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the compact laser amplification system based on a spatial multiplexing structure according to the present invention;

[0024] Figure 2 This is a schematic diagram of a compact laser amplification system based on a spatial multiplexing structure in the first embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the power amplifier system in the first embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the partitioning of the gain medium in the first embodiment of the present invention;

[0027] Figure 5 This is a graph showing the relationship between flux density and signal light input energy in the first embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of a compact laser amplification system based on a spatial multiplexing structure in the second embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram of the deformed structure of the compact laser amplification system based on a spatial multiplexing structure in the second embodiment of the present invention;

[0030] In the diagram: 1. Seed laser source; 2. Beam expander; 3. Shaping device; 4. Polarizing beam splitter; 5. Faraday isolator; 6. Power amplifier system; 7. Encoding prism; 8. Mirror.

[0031] 6-1. Laser diode array 6-2. Pump light collimation device 6-3. Isolation plate 6-4. Cooling medium 6-5. Gain medium Detailed Implementation

[0032] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0034] The compact laser amplification system based on a spatial multiplexing structure proposed in this application, Figure 1 The overall structure of the laser amplification system includes: a seed laser 1, a beam expander 2, a power amplifier system 6, and a beam transmission encoding device.

[0035] Seed source laser 1 outputs signal light, the center wavelength of which matches the emission spectrum of gain medium 6-5, and the energy, time waveform and spectral distribution of the signal light output by seed source laser 1 can be selected according to requirements.

[0036] The beam expander 2 is set on the signal light optical path to expand the signal light beam. At least one beam expander 2 is set in the entire signal light transmission and amplification optical path, and multiple beam expanders 2 can also be set according to the specific requirements of signal light amplification. Each beam expander 2 can also be set to multiple stages to realize multi-stage amplification of the signal light.

[0037] The power amplifier system 6 includes two sheet-like gain dielectrics 6-5 located in the middle layer, and a cooling dielectric 6-4, an isolation plate 6-3, and a laser pumping device arranged sequentially on both sides of the gain dielectrics 6-5 as the center. The power amplifier system 6 can be configured as a symmetrical structure with the two gain dielectrics 6-5 as the center of symmetry, or it can be an asymmetrical structure with the two gain dielectrics 6-5 arranged in a staggered manner.

[0038] The surfaces of the two gain media 6-5 that are in contact with the cooling medium 6-4 are coated with a high-reflectivity film for signal light and a high-transmittance film for pump light. The surfaces of the two gain media that are opposite each other are coated with a high-transmittance film for signal light and a high-reflectivity film for pump light. This ensures that the signal light is refracted back and forth between the two gain media for multi-path amplification. The pump light enters the gain media through the surface coated with the high-transmittance film for pump light and is absorbed. Then it is reflected by the surface of the gain media coated with the high-reflectivity film for pump light and is absorbed again. As an example, the surface of the gain media 6-5 is coated with an absorbing material that absorbs spontaneous emission amplified light beams.

[0039] The isolation plate 6-3, cooling medium 6-4, and gain medium 6-5 form a three-piece structure, allowing the cooling medium to be isolated from the outside environment through the gain medium 6-5 and the isolation plate 6-3. Both surfaces of the isolation plate 6-3 outside the gain medium 6-5 are coated with a pump light high-transmittance film, ensuring that the pump light can penetrate the isolation plate 6-3 and enter the gain medium. As an example, such as... Figure 3 As shown, the laser pumping device is a laser diode array 6-1, the size of which matches the dimensions of the gain medium 6-5. Because the fast axis divergence of the laser diodes is significant, a specific pump light collimation device 6-2 is required for this pumping system to ensure uniform irradiation of the gain medium by the pump light, thereby improving the efficiency of the pump coupling process. The pump light collimation device 6-2 includes, but is not limited to, optical fibers, microlens arrays, cylindrical lenses, and conical light tubes.

[0040] The aforementioned power amplifier system 6 employs an activated reflector configuration for signal light amplification. In this configuration, the signal light obliquely enters the gain medium from the lower surface of any gain medium, is reflected by the upper surface of the gain medium, and then refracted out of the gain medium by the lower surface. The signal light only needs to propagate within the gain medium, effectively decoupling it from the cooling medium and resulting in better beam quality for the output pulse. The signal light beam repeatedly enters the gain medium at different positions and spatial angles. During this process, the beam aperture expands with increasing energy. Therefore, this amplification process is a variable-aperture spatial multiplexing amplification process, requiring a beam expander and a beam transmission conversion device to handle the beam aperture changes, angle variations, and movement during amplification.

[0041] The beam transmission encoding device is a combination of a reflector, a retroreflector, an encoding prism, a Faraday isolator, and a polarizing beam splitter. It works in conjunction with the power amplifier system 6 to guide the signal light into the gain medium of the power amplifier system and change the transmission direction and polarization state of the signal light, so that the signal light is amplified in multiple stages between the two gain media of the power amplifier system. The beam transmission encoding device makes the direction of the signal light during the last stage of amplification orthogonal to the direction of the signal light during the previous stage of amplification. Each of the above amplification stages is a single-pass amplification or a multi-pass amplification.

[0042] In a beam transmission encoding device, the signal light is repeatedly passed through a gain medium to achieve multi-path amplification via a reflector, retroreflector, or encoding prism. The reflector, retroreflector, or encoding prism encodes the number of times the signal light is amplified. The combination of a reflector or Faraday isolator and polarizing beam splitter outputs the signal light amplified by the gain medium.

[0043] In addition, the laser amplification system also includes a shaping device 3, which is set on the signal light path to control the size, spot shape and intensity distribution of the signal light.

[0044] Example 1

[0045] Please see Figures 2-5 This is one of the preferred solutions in this application.

[0046] like Figure 2 The diagram shows a schematic of a compact laser amplification system based on a spatial multiplexing structure. This laser amplification system includes a seed laser 1, a beam expander 2, a shaping device 3, a polarizing beam splitter 4, a Faraday isolator 5, a power amplifier system 6, an encoding prism 7, and a reflector 8 for reflecting the signal light after the first five stages of amplification back along its original path, arranged sequentially along the signal light transmission path. The polarizing beam splitter 4, Faraday isolator 5, encoding prism 7, and reflector 8 constitute the beam transmission encoding device in this embodiment. Two beam expanders 2 are provided; the first beam expander 2 performs the first beam expansion of the signal and is positioned before the shaping device 3; the second beam expander 2 is positioned after the polarizing beam splitter 4 and expands the signal light for the final stage of amplification.

[0047] In this embodiment, the sheet-like gain medium 6-5 is made of Yb:YGG crystal with a doping concentration of 1.33%, and is end-pumped using a high-power-density laser diode array 6-1. The size of a single gain medium is approximately 60mm × 35mm × 6mm. Figure 4 As shown, the 60mm×35mm surface of the gain medium 6-1 is divided into 5 regions. By spatial multiplexing, the signal light undergoes 10 amplification passes through the beam transmission encoding device in these 5 regions. Then, the beam expander 2 set in the 11th amplification optical path is used to expand the signal light again, completing the final high-throughput energy extraction.

[0048] Seed laser 1 provides a fundamental mode pulse signal light with nanojoule-level energy and a rectangular time waveform. This signal light then passes through beam expander 2 and shaping device 3 to modulate it into a square spot with a flat-top spatial intensity distribution and an aperture of 10mm × 10mm. During the amplification process, the signal light passes sequentially through the first five regions of gain medium 6-5 via the coding prism 7. Figure 4 The first five stages of amplification are completed in the areas marked 1-5. Then, the signal light is returned along the original path via the plane mirror 8, and the encoding area of ​​the gain medium 6-5 is reused to achieve the amplification of the 6th to 10th stages. Figure 4(The area is marked as 6-10). In the first 1-9 amplification passes, since the energy density of the signal light is relatively low, it can be approximated as a small-signal amplification process, with a single-pass gain of approximately 8 times. At this point, the energy of the signal light reaches the joule level. In the 10th amplification pass, since the energy density of the signal light is close to the saturation flux of the gain medium, this amplification pass is an energy extraction process, increasing the signal light energy to the order of ten joules. At this point, it can be considered that the energy in this area has been basically extracted. After the 10th amplification pass is completed, the signal light is guided out by the polarizing beam splitter prism 4 and the Faraday isolator 5, and then expanded to 20mm × 20mm by the beam expander 2. Then, the 11th amplification pass is performed. In the 11th amplification pass, the direction of the signal light traveling in the gain medium 6-5 is orthogonal to that of the first 10 amplification passes, and its energy extraction area is... Figure 4 The range circled in the middle, after the final high-throughput extraction, ultimately results in an output pulse energy greater than 50J.

[0049] By employing an activated reflector structure, an efficient and compact spatial multiplexing arrangement of the signal light gain path is achieved on two gain media, realizing the goals of high-gain amplification in the pre-stage and high-throughput amplification in the post-stage. Ultimately, this realizes the design concept of miniaturization and lightweighting of the laser, greatly expanding the application scenarios and scope of the laser.

[0050] like Figure 5 The figure shows the relationship between the flux density output from the 10th and 11th stages of a Yb:YGG crystal with a gain medium doping concentration of 1.33% and the input energy of the signal light. Since the beam cross-section size decreases and the flux density increases as the laser exits the crystal, and given the same laser beam aperture, the flux of the subsequent stage should be higher than that of the preceding stage. In this embodiment, the output signal light from the 10th stage is beam-expanded, so the flux density of the signal light at the 10th and 11th stages reaches its maximum value before beam expansion, making it most likely to damage the crystal. In this laser power amplification system, with changes in the signal light, the flux density at the three exit points in the figure does not exceed 15 J / cm². 2 It will not cause damage to the device if it is below the current damage resistance threshold of the device and coating.

[0051] Example 2

[0052] Please see Figures 6-7 This is one of the preferred solutions in this application.

[0053] like Figure 6The diagram shows a compact laser amplification system based on a spatial multiplexing structure. This system includes: a seed laser 1, two Faraday isolators 5, three beam expanders 2, a shaping device 3, a power amplifier system 6, and two encoding prisms 7. The connection is as follows: the seed laser 1 outputs signal light, which passes through the first Faraday isolator 5 and the first beam expander 2 before entering the power amplifier system 6. It then undergoes amplification through the first encoding prism 7 for stages 1 through 8. After the 8th stage of amplification, the signal light is output from the power amplifier system and passes through the second beam expander 2. After beam expansion and shaping device 3 (a soft-edge aperture is used in this embodiment) controls the beam distribution and the second Faraday isolator 5, the light enters the power amplifier system 6 and is amplified through the second encoding prism 7 for 9-11 passes. Finally, the light is exported from the power amplifier system. The exported signal light is expanded by the third beam expander 2 and then enters the power amplifier system. It travels in a direction orthogonal to the direction of travel of the amplified signal light for 1-11 passes. After the final stage of amplification in the two gain media, it is exported. In this embodiment, the final stage of amplification is only a single pass, that is, the 12th pass. Alternatively, it can be as follows: Figure 7 As shown, an encoding prism 7 is set on one side of the power amplifier system 6 to make the last stage of amplification a multi-pass amplification, such as the 12th and 13th passes in the figure.

Claims

1. A compact laser amplification system based on a spatial multiplexing structure, characterized in that, The laser amplification system includes: a seed laser, a beam expander, a power amplifier system, and a beam transmission encoding device; The seed source laser outputs signal light; The beam expander is installed on the signal light path to expand the signal light beam; The power amplifier system includes two sheet-like gain media located in the middle layer, and a cooling medium, an isolation plate, and a laser pumping device arranged sequentially on the outside of the two gain media. The surfaces of the two gain media that are in contact with the cooling media are coated with a high-reflectivity film for signal light and a high-transmittance film for pump light, and the surfaces of the two gain media that are opposite to each other are coated with a high-transmittance film for signal light and a high-reflectivity film for pump light. Both surfaces of the isolation plate are coated with a pump light high-transmittance film. The beam transmission encoding device works in conjunction with the power amplifier system to guide the signal light into the gain medium of the power amplifier system and change the transmission direction and polarization state of the signal light, so that the signal light is amplified in multiple stages between the two gain media of the power amplifier system. In the last stage of amplification, the beam transmission encoding device changes the direction of travel of the signal light so that its direction of travel is orthogonal to the direction of travel of the signal light in the previous stage of amplification.

2. The compact laser amplification system based on a spatial multiplexing structure according to claim 1, characterized in that, The center wavelength of the signal light output by the seed source laser is matched with the emission spectrum of the gain medium, and the energy, time waveform and spectral distribution of the signal light output by the seed source laser can be selected according to requirements.

3. The compact laser amplification system based on a spatial multiplexing structure according to claim 1, characterized in that, The laser amplification system also includes at least one beam expander, which is disposed on the signal amplification optical path.

4. The compact laser amplification system based on a spatial multiplexing structure according to claim 3, characterized in that, The beam expander performs one or more stages of beam expansion on the signal light.

5. The compact laser amplification system based on a spatial multiplexing structure according to claim 1, characterized in that, The signal light is amplified in multiple stages between the two gain media of the power amplifier system, with each stage being either single-pass or multi-pass amplification.

6. The compact laser amplification system based on a spatial multiplexing structure according to claim 1, characterized in that, The laser amplification system also includes a shaping device, which is disposed on the signal light path.

7. The compact laser amplification system based on a spatial multiplexing structure according to claim 1, characterized in that, The laser pumping device is a laser diode array, and a pump light collimation device may or may not be provided between the laser diode array and the isolation plate.

8. The compact laser amplification system based on a spatial multiplexing structure according to claim 7, characterized in that, The pump light collimation device includes, but is not limited to, optical fibers, microlens arrays, cylindrical lenses, and conical light tubes.

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