基于层状WS_(2)调制激光泵浦的光学参量振荡中红外运转特性  

Operation characteristics of mid-infrared optical parametric oscillation pumped by layered WS_(2) modulated laser

作　　者：王静[1] 逄金波 郭鹤泽 胡新宇 周承辰 唐文婧 蒋锴 夏伟 Wang Jing;Pang Jin-Bo;Guo He-Ze;Hu Xin-Yu;Zhou Cheng-Chen;Tang Wen-Jing;Jiang Kai;Xia Wei(School of Physics and Technology,University of Ji’nan,Ji’nan 250022,China;Institute for Advanced Interdisciplinary Research(IAIR),University of Ji’nan,Ji’nan 250022,China)

机构地区：[1]济南大学物理科学与技术学院,济南250022 [2]济南大学前沿交叉科学研究院,济南250022

出　　处：《物理学报》2022年第2期97-106,共10页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:62005049,51802116,61308057);山东省自然科学基金(批准号:ZR2019BEM040);济南市资助引进创新团队项目基金(批准号:2018GXRC011)资助的课题。

摘　　要：光学参量振荡器是重要的中红外相干光源.近年来,在激光调制方面,二维过渡金属硫化物展现了非线性可饱和吸收特性,因此有望成为光学参量振荡器基频激光的优良调制元件.本工作中,首先,实验测量了层状二硫化钨(WS_(2))调制固体激光的输出特性.其次,结合主动声光Q开关,实现了主被动双调Q光参量振荡的运转,得到了纳秒脉冲宽度的中红外脉冲,并研究了WS_(2)对光参量转换的优化特性,发现WS_(2)纳米片除了能够压缩脉冲、提高峰值功率外,还能缓解单主动调Q光学参量振荡器中的"输出饱和下降"现象,这种现象可能起因于砷酸钛氧钾(KTiOAsO_(4),KTA)的制冷不均匀.WS_(2)的可饱和吸收效应能够显著压缩光斑,减少高斯光斑的边缘能量,因此能够缓解KTA的温度梯度分布,从而优化输出特性.最后,基于WS_(2)的非线性透过率曲线,考虑非均匀展宽机制和大信号下的非饱和吸收,计算了WS_(2)的可饱和吸收特性参数,并求解了层状WS_(2)调制光学参量振荡器的速率方程组.本文在实验上展示了二维过渡金属硫化物对激光非线性频率变换的优化效果,尤其是对热效应的缓解;同时,为二维材料调制激光的动力学模拟提供了参数依据.Optical parametric oscillator(OPO)is an important mid-infrared coherent light source.Two-dimensional(2D)transition metal dichalcogenide(TMDC)with nonlinear absorption of near-infrared-wavelength light is expected to be a prospective modulating switch for OPO’s fundamental laser.In this work,firstly,the characteristics of a home-made 3.5 nm-thick tungsten disulfide(WS_(2))sample are measured and analyzed.The nonlinear transmission is figured and fitted,revealing the performance of WS_(2)’s saturable absorption.Then,the output characteristics of WS_(2)saturable absorber(SA)modulated solid-state laser are measured experimentally.Although the photon energy of 1.06μm-wavelength laser is less than the bandgap energy of 3.5 nm WS_(2),the sample still exhibits the saturable absorption.This may be attributed to the mechanisms of defect-induced absorption,coexistence of states,edge-state of material,two-photon absorption,etc.Secondly,combined with active acousto-optic(AO)modulator,the active and passive Q-switched OPO with idler-light oscillation are implemented,and the nanometer pulse-width mid-infrared pulse is obtained.The implementation of AO modulator is to manage the regular switching time to reduce the pulse peak-to-peak vibration of fundamental light and improve the peak power.The optimal characteristics of WS_(2)for OPO are studied.Based on the saturable absorption characteristics,the output pulse is compressed by 60%,the peak power is improved by 191%,and the stability of pulse train is improved by 79.62%.Especially,the insertion of WS_(2)nanosheet could alleviate the“output saturation and drop”phenomenon in singly active-Q-switched OPO.This phenomenon may origin from the uneven refrigeration of KTA.Because the saturable absorption effect of WS_(2)can significantly reduce the transverse area of Gaussian beam,it can alleviate the temperature gradient distribution of KTA and optimize the output characteristics.Finally,based on the nonlinear transmittance curve measured for WS_(2),the absorption cross secti

关 键 词：层状过渡金属硫化物 中红外光学参量振荡器 动力学方程 可饱和吸收截面 

分 类 号：TN24[电子电信—物理电子学]