1 河北工业大学电子信息工程学院先进激光技术研究中心，天津 300401
2 河北工业大学河北省先进激光技术与装备重点实验室，天津 300401
3 哈尔滨工业大学可调谐激光技术国家重点实验室，黑龙江 哈尔滨 150080
利用中心波长为800 nm、脉冲宽度为35 fs的飞秒激光脉冲开展了以蓝宝石晶体为介质的超连续白光光谱特性研究，通过对比不同入射脉冲能量下焦距为40 mm的球面透镜产生的白光光谱发现：随着入射脉冲能量的增强，白光光谱向蓝边方向展宽，当能量增加到210 nJ时，光谱范围不再变化。对比焦距为40 mm的球面透镜和消色差透镜产生的白光光谱发现：消色差透镜产生的光谱的整体强度小于球面透镜，且光谱有一定蓝移，蓝移波长可达450 nm。采用Zemax软件对两种透镜产生的焦斑进行仿真，比较了两种透镜产生的焦斑的大小和能量，并分析了蓝移现象产生的原因。同时，本研究对比了焦距为40 mm和100 mm球面透镜、消色差透镜产生的白光光谱的范围和稳定性，结果表明，焦距为40 mm的透镜产生的白光光谱的稳定性较好，光谱范围较宽，约为450～700 nm。罗丹明B的瞬态吸收实验结果表明，使用焦距为40 mm的消色差透镜时，罗丹明B的瞬态吸收信号最为明显，信噪比最高。本实验表明，针对不同的样品特性，可以通过选择不同的透镜来优化瞬态吸收实验结果。
非线性光学 飞秒激光 超连续白光 瞬态吸收 中国激光
2022, 49(11): 1111003
Author Affiliations
Abstract
1 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai201800, China
2 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai201800, China
White-light continuum can be induced by the interaction of intense femtosecond laser pulses with condensed materials. By using two orthogonal polarizers, a self-induced birefringence of continuum is observed when focusing femtosecond laser pulses into bulk fused silica. That is, the generated white-light continuum is synchronously modulated anisotropically while propagating in fused silica. Time-resolved detection confirms that self-induced birefringence of continuum shows a growth and saturation feature with time evolution. By adjusting laser energy, the transmitted intensity of continuum modulated by self-induced birefringence also varies correspondingly. Morphology analysis with time evolution indicates that it is the focused femtosecond laser pulses that induce anisotropic microstructures in bulk fused silica, and the anisotropic structures at the same time modulate the generated continuum.
femtosecond laser pulses fused silica self-induced birefringence white-light continuum High Power Laser Science and Engineering
2020, 8(2): 02000e19
