激光远场大气稳定传输的光场调控技术研究

大部分激光器产生的激光为相干光束,在理想环境下,激光到达远场后其相干特性与出射时保持一致,且光强分布均匀,但由于大气环境中湍流的存在,激光到达远场后发生相互干涉,产生振幅起伏,即光强闪烁现象。文中主要从多个角度分析该现象形成的原因,并主要从相位、偏振态两个方面出发,提出相应的解决措施,并完成验证实验。实验结果表明,所提出的解决措施可实现较好的分布效果;又从理论方面提出了光源光束整形措施,提升激光远场光斑分布的性能;最后结合实际应用,分析了高空相对于地面大气湍流的区别,以及激光传输角度对激光远场传输的影响。从实际应用方面,涵盖针对激光远场大气传输能量稳定性的多项解决方案,用于指导启发同领域内相关技术的攻关,具体问题可根据文中原理内容提出具体实现方式。

The 266-nm ultraviolet-beam generation of all-fiberized super-large-mode-area narrow-linewidth nanosecond amplifier with tunable pulse width and repetition rate

We report on a compact, stable, all-fiberized narrow-linewidth(0.045 nm) pulsed laser source emitting laser beam with a wavelength of 266 nm, and tunable pulse width and repetition rate. The system is based on all-fiberized nanosecond amplifier architecture, which consists of Yb-doped fiber preamplifiers and a super-large-mode-area Yb-doped fiber power amplifier. The fiber amplifier with a core of 50 μm is used to raise the threshold of the stimulated Brillouin scattering(SBS) effect and to obtain high output power and single pulse energy. Using lithium triborate(LBO) crystal and betabarium borate(BBO) crystal for realizing the second-harmonic generation(SHG) and fourth-harmonic generation(FHG),we achieve 17 μJ(1.73 W) and 0.66 μJ(66 mW), respectively, at wavelengths of 532 nm and 266 nm and a repetition rate of 100 kHz with pulse width of 4 ns. This source has great potential applications in fluorescence research and solar-blind ultraviolet optical communication.

Influence of optical nonlinearity on combining efficiency in ultrashort pulse fiber laser coherent combining system

The influence of optical nonlinearity on combining efficiency in ultrashort pulse fiber laser coherent combining system is investigated theoretically and experimentally.In the theoretical work,a new theoretical algorithm is presented for the coherent combining efficiency,which can be used to quantify the spectral coherence decay induced by optical nonlinearity imbalance between the sub-beams.The spectral information of the sub-beam is obtained by numerically solving the nonlinear Schrödinger equation(NLSE)in this algorithm to ensure an accurate prediction.In the experimental work,the coherent combining of two all-fiber picosecond lasers is achieved,and the influence of imbalanced optical nonlinearity on the combining efficiency is studied,which agrees with the theoretical prediction.This paper reveals the physical mechanism for the influence of optical nonlinearity on the combining efficiency,which is valuable for the coherent combining of ultrashort pulse fiber laser beams.

An All-Fiberized Chirped Pulse Amplification System Based on Chirped Fiber Bragg Grating Stretcher and Compressor

We report an all-fiberized chirped pulse amplification system without any bulk devices.The stretcher and compressor are chirped fiber Bragg gratings inscribed in a 6/125μm single-mode fiber and a 30/250μm largemode-area fiber.The fabrication system of chirped fiber Bragg gratings was designed and built by ourselves.The width of the linear exposure spot was controlled according to the different fiber sizes to improve the fabrication quality,and the parameters of chirped fiber Bragg gratings were fine-tuned during the fabrication to achieve the overall system’s spectral matching.Two fiber circulators with the same fiber sizes as the chirped fiber Bragg gratings were employed to auxiliarily achieve the pulse stretching and compression.The dispersion accumulations provided by the stretcher and compressor are 129.8 ps and 90.8 ps.The power amplifiers were composed of the two-stage 10/130μm fiber pre-amplifier and the 30/250μm fiber main amplifier.The proposed chirped pulse amplification system with no spatial light is the true sense of an all-fiberized chirped pulse amplification structure and shows the main trend in development of ultrashort pulse fiber lasers.