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CN-122026214-A - Traveling wave amplifying device and method based on thermal lens imaging

CN122026214ACN 122026214 ACN122026214 ACN 122026214ACN-122026214-A

Abstract

The invention discloses a traveling wave amplifying device and a traveling wave amplifying method based on thermal lens imaging, wherein the device comprises a laser seed source for outputting seed laser with initial power and frequency, a traveling wave amplifying system is connected in series on an output light path of the seed laser in multiple stages, each traveling wave amplifying system comprises a laser isolating module, a plano-convex lens, a laser crystal, a plano-concave dichroic mirror and a pumping source module, the laser crystal forms an equivalent thermal lens under the action of pumping light of the pumping source module, in each traveling wave amplifying system, the seed laser realizes double-pass amplification in the laser crystal based on light path reflection of the plano-concave dichroic mirror, and the laser mode radius of round trip passing through the laser crystal tends to be consistent based on thermal lens imaging, and a double-pass single-grating compressing system is used for pulse time domain compression.

Inventors

  • TIAN WENLONG
  • ZHANG FENGCHEN
  • ZHU JIANGFENG
  • WANG GEYANG
  • YU YANG
  • WEI ZHIYI

Assignees

  • 西安电子科技大学

Dates

Publication Date
20260512
Application Date
20260129

Claims (10)

  1. 1. A traveling wave amplification device based on thermal lens imaging, comprising: The laser seed source (1) is used for outputting seed laser with initial power and frequency and has the function of adjusting the laser output frequency; The traveling wave amplification system (5), the traveling wave amplification system (5) has multiple stages and is connected in series on the output light path of seed laser, each stage of the traveling wave amplification system (5) comprises a laser isolation module (51), a plano-convex lens (52), a laser crystal (53), a plano-concave dichroic mirror (54) and a pump source module (55), the laser isolation module (51), the plano-convex lens (52), the laser crystal (53) and the plano-concave dichroic mirror (54) are sequentially arranged corresponding to the incidence direction of the seed laser, the laser isolation module (51) is used as incidence and reverse output nodes of the seed laser, the laser crystal (53) forms an equivalent thermal lens under the action of the pump light of the pump source module (55), in each stage of the traveling wave amplification system, the seed laser realizes double-pass amplification in the laser crystal (53) based on the light path reflection of the plano-concave dichroic mirror (54), and the radius of the laser mode of the laser passing through the laser crystal tends to be consistent based on the thermal lens imaging; And the double-pass single-grating compression system (6) is used for performing dispersion compensation and pulse time domain compression on the laser pulse after passing through the multistage traveling wave amplification system.
  2. 2. A thermal lens imaging based traveling wave amplification device according to claim 1, characterized in that the laser seed source (1) comprises an oscillator, a stretcher and a laser amplifier, which are arranged in sequence and are capable of outputting femtosecond laser pulses in the order of picoseconds to nanoseconds.
  3. 3. The traveling wave amplification device based on thermal lens imaging according to claim 1, further comprising a power adjustment module (2), wherein the power adjustment module (2) is arranged between the laser seed source (1) and the initial traveling wave amplification system (5), and the power adjustment module (2) is used for adjusting laser power injected into the traveling wave amplification system (5).
  4. 4. A traveling wave amplifying device based on thermal lens imaging according to claim 3, wherein the power adjusting module (2) comprises a half-wave plate and a polarizing beam splitter, the half-wave plate and the polarizing beam splitter are located on the optical path of the seed laser, and the power adjustment of the seed laser injected into the traveling wave amplifying system (5) is achieved by rotating the half-wave plate to adjust the polarization state of the laser and splitting the laser through the polarizing beam splitter.
  5. 5. The traveling wave amplifying device based on thermal lens imaging according to claim 3, further comprising a laser isolator (3) and a laser shaping module (4), wherein the laser isolator (3) and the laser shaping module (4) are arranged between the power adjusting module (2) and the initial traveling wave amplifying system (5), the laser isolator (3) is used for setting laser light in a spectral range of 1000nm-1100 nm to pass through in a P polarization forward direction, the laser shaping module (4) is a galilean telescope system combined by a plano-concave lens and a plano-convex lens or a kepler telescope system combined by a plano-convex lens, and the laser shaping module (4) is used for performing beam expansion processing on the passing seed pulses.
  6. 6. The traveling wave amplifying device based on thermal lens imaging according to claim 1, wherein the laser isolation module (51) comprises a polarization beam splitter, a half-wave plate and a rotator, the polarization beam splitter, the half-wave plate and the rotator are sequentially arranged on a light path of seed laser, and the laser isolation module (51) can forward pass P polarized light and reversely deflect 90 degrees to output S polarized light based on the polarization beam splitter.
  7. 7. The traveling wave amplifying device based on thermal lens imaging according to claim 1, wherein the traveling wave amplifying system (5) further comprises a pump shaping module (56), the pump shaping module (56) is arranged between the pump source module (55) and the laser crystal (53), the pump shaping module (56) is a fixed proportion lens group imaging system, and can enable pump light to enter the laser crystal after being subjected to beam expansion focusing in a proper proportion, so that matching and energy coupling of a crystal position pump light spot and a seed pulse light spot mode are achieved.
  8. 8. The traveling wave amplifying device based on thermal lens imaging according to claim 1, wherein the dual-pass single-grating compression system (6) is further capable of compensating for second and third order dispersion introduced during the amplification of seed pulses by the traveling wave amplifying system, the dual-pass single-grating compression system (6) comprises a thin film polarizer (61), an optical isolation unit (62), a mirror group (63), a high-efficiency transmission diffraction grating (64), a plane long-strip mirror (65), a first roof prism (66), a second roof prism (67) and a plane mirror (68), the single diffraction efficiency of the high-efficiency transmission diffraction grating (64) is greater than 99%, the second roof prism (67) is horizontally located on a side of the high-efficiency transmission diffraction grating (64) away from the plane long-strip mirror, laser pulses amplified by the multi-stage traveling wave amplifying system are injected into the optical isolation unit (62) via the thin film polarizer (61), and are incident on the high-efficiency transmission diffraction grating (64) at a littrow angle after being adjusted by the mirror group (63), the laser pulses are transmitted back to the first roof prism (64) in a vertical direction after being diffracted by the first roof prism (65) and then travel back to the first roof prism (67) in a low-order diffraction mode, the laser pulse is guided out by a plane 45-degree incidence angle reflecting mirror (69), returned by a plane reflecting mirror (68) along the original path for second pulse compression, reflected to a light isolation unit (62) by the laser pulse subjected to the second compression and reversely deflected by a thin film polarizer (61) for 90 degrees to output S polarized light.
  9. 9. The traveling wave amplification device based on thermal lens imaging according to any one of claims 1 to 8, wherein said laser crystal (53) is an ytterbium-doped laser crystal comprising Yb CALGO crystal, yb CALYO crystal, yb YAG crystal, yb CaF2 crystal, yb YLF crystal.
  10. 10. A method of traveling wave amplification apparatus based on thermal lens imaging, using the traveling wave amplification apparatus according to claim 9, comprising: Providing a seed light source; pulse widening and power pre-amplification are carried out on the seed light source; Introducing a seed light source with power pre-amplification into a multistage traveling wave amplification system connected in series, carrying out double-pass amplification on the seed light source in an ytterbium-doped laser crystal in each stage of traveling wave amplification system, and maintaining stable mode matching in the amplification process based on a thermal lens imaging principle; And injecting the seed light source subjected to multistage amplification into a double-pass single-grating compression system to perform pulse compression.

Description

Traveling wave amplifying device and method based on thermal lens imaging Technical Field The invention belongs to the technical field of ultrafast lasers, and particularly relates to a traveling wave amplifying device and method based on thermal lens imaging. Background The high-energy femtosecond laser system is a core technical tool for exploring industrial processing and front-edge physics, and has irreplaceable application value in front-edge fields such as higher harmonic generation, terahertz radiation regulation and control, optical parameter amplification, precise micro-nano processing and the like. However, the performance improvement of the current mainstream high-energy femtosecond laser system is still limited by the dual constraints of the gain medium characteristics and the system design, and the breakthrough of the bottleneck in the prior art is needed. The traveling wave amplification technology can effectively realize the core advantages of laser energy and power improvement, and is widely applied to a plurality of key fields such as industrial processing, scientific research and detection, medical equipment, national defense safety and the like. With the continuous improvement of the laser output performance requirements of each application scene, the output power and energy of the traveling wave amplification system are further improved, the long-term stability of the output laser is ensured, and the traveling wave amplification system becomes a core target to be broken through in the technical field. However, during the actual design and operation of the row wave amplification, the thermal lens effect is always a key bottleneck problem that restricts the improvement of the system performance. When laser light is transmitted in the gain medium and energy amplification is achieved, the gain medium may generate heat accumulation by absorbing a portion of the laser energy. Because of the uneven heat distribution (such as temperature gradient along radial direction) in the gain medium, the refractive index of the gain medium will correspondingly change unevenly, and the change makes the gain medium equivalent to a thermal lens, namely a thermal lens effect. During the propagation amplification, the gain medium is inevitably subjected to the pump thermal load to produce a thermal lens effect. The thermal lens effect changes the equivalent refractive index profile of the laser crystal, thereby introducing additional focusing or diverging effects, resulting in distortion of the wavefront of the amplified light beam during transmission, and significant degradation of the beam quality. Therefore, the mode matching condition and the amplification efficiency of the traveling wave amplification system are reduced, and the stable operation capability of the system under the conditions of high power and high energy is limited. In addition, from the aspect of output stability, the equivalent focal length of the thermal lens can dynamically fluctuate along with the changes of working time, pumping conditions and injection energy, so that key parameters such as laser output spot size, divergence angle, focusing position and the like are unstable, and the requirements of application scenes such as industrial precision machining, high-stability scientific research measurement and the like on laser output consistency and long-term stability are difficult to meet. Therefore, how to accurately and efficiently compensate the thermal lens effect becomes a core difficulty in the design process of the traveling wave amplification system. In the existing compensation scheme, a passive compensation mode (such as selecting a gain medium with a low thermo-optical coefficient and optimizing a cooling structure) is partially adopted, but the compensation precision of the scheme on the thermal lens effect is limited, the dynamic thermal lens change under a complex working condition is difficult to deal with, and the other active compensation scheme (such as a compensation technology based on a deformable mirror and a liquid crystal spatial light modulator) can realize dynamic adjustment, but generally has the problems of complex system structure, high cost, difficult compromise of response speed and compensation precision and the like, and cannot realize large-scale popularization in practical engineering application. In summary, in the development process of the current traveling wave amplification technology, the core problems of bottleneck power/energy improvement, degradation of output beam quality, insufficient output power stability and the like caused by the thermal lens effect are needed to overcome, but the existing thermal lens compensation scheme generally has the defects of complex principle, poor adaptability or over-high cost and the like, so that the technical upgrading requirement is difficult to meet. Therefore, how to provide a traveling wave amplifying device and a traveling wave amplifying method bas