基于非线性相位解调的光纤激光光谱压窄技术研究  

Spectrum-Narrowing Technique for Fiber Laser Using Nonlinear Phase Demodulation

作　　者：任翼科 沈辉 汪贺 谢威 杨依枫 漆云凤 Ren Yike;Shen Hui;Wang He;Xie Wei;Yang Yifeng;Qi Yunfeng(Shanghai Key Laboratory of All Solid State Laser and Application Technology,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;University of Chinese Academy of Sciences,Beijing 100049,China;Shanghai Key Lab of Modern Optical System,Engineering Research Center of Optical Instruments and Systems,Ministry of Education,University of Shanghai for Science and Technology,Shanghai 200093,China)

机构地区：[1]中国科学院上海光学精密机械研究所上海市全固态激光及应用技术重点实验室,上海201800 [2]中国科学院大学,北京100049 [3]上海理工大学光学仪器与系统教育部工程中心上海市现代光学系统重点实验室,上海200093

出　　处：《中国激光》2024年第22期144-153,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金青年科学基金(62205357)。

摘　　要：窄线宽光纤激光器的输出功率由于受到受激布里渊散射(SBS)效应的限制而很难提升。相位调制光谱展宽技术能有效抑制SBS,然而在一定线宽条件下,该技术对SBS阈值的提升效果依然有限。为了提升SBS的阈值,采用多级相位或频率调制(FM)技术来展宽光谱。同时,通过幅度调制(AM)产生的自相位调制(SPM)效应,可以在输出光谱中引入频率啁啾。这种频率啁啾有助于输出光谱的相位解调和载波恢复,进而实现光谱的压窄。通过对非线性解调过程进行理论建模,详细分析了解调相位对光谱压缩效果的影响,研究了输出激光功率与调制深度的关系,探究了该技术对SBS阈值的影响。结果表明,该技术可以与一般的相位调制方式相结合,实现近2倍的SBS阈值提升。Objective Owing to the high efficiency,excellent monochromaticity and beam quality,stable and reliable operation,and high environmental adaptability,high-power narrow-linewidth fiber lasers are widely applicable to various fields,such as spectral-beam combining (SBC),coherent-beam combining (CBC),nonlinear frequency conversion,remote-sensing measurement,and gravitational-wave detection.The development of application technologies has increased the demand for power scaling narrow-linewidth fiber lasers.To achieve prominent effects in SBC and CBC,a gigahertz spectral linewidth is typically required.Narrowing the linewidth and increasing the power simultaneously are challenging owing to nonlinear effects,in particular the stimulated Brillouin scattering (SBS) effect.To suppress SBS,researchers have proposed many methods,such as increasing the optical fiber-mode field area,reducing the optical-fiber length,optimizing the pump structure of the main amplifier,introducing gain competition,applying a temperature or stress gradient to broaden the Brillouin gain spectrum,and phase modulation.Among them,phase modulation can mitigate SBS by broadening the seed linewidth to effectively reduce the spectral power density of the laser;thus,it has been extensively investigated recently.However,improvement to the SBS threshold is limited under a certain linewidth.Nonlinear spectrum compression with a negative chirp is widely used in pulsed-fiber amplifiers.To reduce the SBS gain,the self-phase modulation (SPM) generated by the nonlinear Kerr effect is employed for phase demodulation and carrier recovery.Notably,this technique is applicable to continuous-wave laser domains.Multistage phase or frequency modulation (FM) is adopted to obtain a relatively wide spectrum and achieve a high-power output.Subsequently,the SPM generated in the fiber can be controlled via amplitude modulation (AM) to narrow the output spectrum.Consequently,power scaling with a narrow linewidth is achieved.Methods In this study,the principle of nonlinear phase

关 键 词：窄线宽光纤激光器 受激布里渊散射 自相位调制 相位调制 幅度调制 

分 类 号：TN248.1[电子电信—物理电子学]