基于液晶空间光调制器进行光谱调制的飞秒啁啾脉冲放大系统  

Femtosecond Chirped Pulse Amplification System with Liquid Crystal Spatial Light Modulator for Spectral Modulation

作　　者：段雨飞 李峰[1] 杨直[1] 李强龙[1] 杨洋[1] 吴天昊 王屹山[1] 杨小君[1] Duan Yufei;Li Feng;Yang Zhi;Li Qianglong;Yang Yang;Wu Tianhao;Wang Yishan;Yang Xiaojun(State Key Laboratory of Transient Optics and Photonics,Xi’an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,Xi'an,Shaanxi 710119,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,陕西西安710119 [2]中国科学院大学,北京100049

出　　处：《中国激光》2021年第11期32-40,共9页Chinese Journal of Lasers

基　　金：国防基础科研计划(JCKY2016130B203);国家自然科学基金(61690222,61805274)。

摘　　要：飞秒光纤激光器具有良好的光束质量与稳定性,被广泛应用于精细材料加工行业。目前工业化光纤飞秒激光器主要是通过啁啾脉冲放大系统的多级放大来实现其高功率,可是多级放大过程会导致严重的增益窄化效应,限制最终的压缩脉冲宽度。为了解决增益窄化问题,缩短脉冲宽度,提高峰值功率,达到更好的“冷”加工效果,提出一种基于空间光调制器的光谱整形系统,通过加载到空间光调制器上的灰度图,产生中心凹陷、平顶等特殊光谱形状,放大后的光谱宽度与初始的种子源保持一致。与未加光谱调制相比,光谱调制后的光谱宽度从7 nm提高到9.5 nm,对应的极限脉宽从222 fs减少到164 fs左右。最后通过透射式光栅对压缩,得到了平均功率为1.3W的飞秒激光输出,采用高斯拟合的方式测量脉冲,脉冲宽度为170 fs,接近转换极限脉冲。Objective Compared with traditional solid-state lasers,such as slats and wafers,femtosecond fiber lasers have many advantages,including compact structures,good beam quality,stable systems,and good heat dissipation.They are widely used in various application fields,particularly in the field of fine material processing.The current femtosecond fiber laser is mainly used to reduce the problems of nonlinearity and device damage in the amplification process using the chirped pulse amplification technology to obtain a femtosecond laser with its peak power and narrow pulse width meeting processing requirements.Owing to the increase in the energy demand of an industrial fiber laser,the amplification classes also gradually increase,rendering the narrowing effect due to an uneven gain medium increasingly severe and influencing the final spectral width.Thus,its occurrence increases the compressed pulse width limit,reduces the pulse peak power,and severely impacts the thermal diffusion in processing.Currently,the gain narrowing problem of a femtosecond fiber laser can be solved using self-phase modulation,a new amplifying stage system,or dielectric layer filters.However,these approaches can only form fixed spectral modulation,which cannot solve the gain narrowing problem in different amplification or laser systems with different power requirements of the same amplification system.Therefore,programmable devices are proposed to achieve the controllability of spectral modulation.Among them,the liquid crystal spatial light modulator,a common element for beam shaping and pulse shaping,exhibits higher regulating precision than the general acoustooptic filter.For a fiber laser seed source,its spectral width is only a few nanometers or tens of nanometers;the liquid crystal spatial light modulator is more suitable for fiber laser spectral modulation.This study focuses on the characteristics of the spatial light modulator and the requirement of a chirp pulse amplification system for spectral modulation.The solutions of a spectral shapi

关 键 词：激光器 液晶空间光调制器 光纤飞秒激光器﹔光谱调制 增益窄化 啁啾脉冲放大系统 

分 类 号：TN248[电子电信—物理电子学]