摘要
报道了基于锯齿波脉冲抑制自相位调制(SPM)的高功率窄线宽单频脉冲光纤激光放大器.通过优化掺镱(Yb)石英有源光纤的长度,在保证输出功率和转换效率的同时提高单频光纤激光放大器中的受激布里渊散射阈值,并采用脉冲波形为锯齿波的种子光,利用其光强对时间的变化率为常数的特性有效抑制了SPM效应导致的激光光谱展宽现象.主放大级泵浦功率为11.3 W时获得了平均输出功率为3.13 W、脉冲重复频率为20 k Hz的1064 nm单频激光输出;此时脉冲宽度为6.5 ns,对应峰值功率为24 k W,测得光谱线宽仅为83 MHz,接近变换极限水平.与采用常规高斯波形脉冲种子光的对照实验相比,锯齿波形脉冲对SPM所致的光谱展宽具有显著抑制效果,为高功率窄线宽脉冲光纤激光放大器提供了一种行之有效的方法.
Fiber laser system in master oscillator power amplifier(MOPA)scheme is a promising technique for high-power narrow-linewidth laser output.With modulation-generated pulsed seed laser,the fiber MOPA benefits the flexible temporal behavior.However,the spectral linewidth broadening induced by self-phase modulation(SPM)is the main obstacle to achieving high-power single-frequency laser output with narrow spectral linewidth,especially for pulsed fiber MOPA in which the kilowatts level peak power results in strong nonlinearity.The SPM induced linewidth broadening is related to the derivative of light intensity with respect to time(dI/dt).Theoretically,if the dI/dt of the laser pulse is a constant,the SPM process will not generate any new frequency components.Hence,the linewidth broadening can be suppressed.In this work,we demonstrate a high-power single-frequency Yb fiber amplifier at 1064 nm,in which a sawtooth laser pulse is employed to suppress the SPM induced linewidth broadening,for obtaining the output with near-transform-limited narrow linewidth.The sawtooth-shaped seed pulse train is generated through using an electro-optic intensity modulator to modulate the continuous-wave(CW)output of a single-frequency fiber laser.After being pre-amplified,the seed laser with a pulse repetition rate of 20 kHz is coupled into the main amplifier,in which a piece of 0.9-m-long Yb-doped silica fiber with core and clad diameters of 35μm and 250μm,respectively,is used as a gain medium.The seed laser is enhanced to an average power value of 3.13 W under a launched 976-nm pump power value of 11.3 W before the onset of stimulate Brillouin scattering.The pulse energy 157μJ and the pulse width 6.5 ns give a peak power of 24 kW.The spectral linewidth measured using a scanning Fabry-Perot interferometer at the maximum power is only 83 MHz,which is quite close to the 76-MHz transform-limited linewidth of the 6.5-ns sawtooth-shaped pulse.For comparison,we also conduct an experiment with a common Gaussian-shaped seed laser,in which the spectral linewidth is broadened significantly with a peak power value of only 1.5 kW.The results here reveal that the using of the sawtooth-shaped pulse is a promising technique to suppress the SPM induced spectral linewidth broadening in high-peak-power fiber amplifiers and acquire near-transform-limited narrow-linewidth laser output.
作者
盛泉
王盟
史朝督
田浩
张钧翔
刘俊杰
史伟
姚建铨
Sheng Quan;Wang Meng;Shi Chao-Du;Tian Hao;Zhang Jun-Xiang;Liu Jun-Jie;Shi Wei;Yao Jian-Quan(School of Precision Instrument and Optoelectronics Engineering,Tianjin University,Tianjin 300072,China;Key Laboratory of Optoelectronic Information Science and Technology(Ministry of Education),Tianjin University,Tianjin 300072,China;Tianjin Jinhang Institute of Technical Physics,Tianjin 300308,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第21期105-111,共7页
Acta Physica Sinica
基金
国家重点研发计划(批准号:2017YFF0104603)
国家自然科学基金(批准号:61975146,62075159)
山东省重点研发计划(批准号:2019JZZY020206)资助的课题。
关键词
单频光纤激光器
脉冲光纤激光器
自相位调制
窄线宽激光器
single-frequency fiber laser
pulsed fiber laser
self-phase modulation
narrow-linewidth laser
