基于分子准直效应的超快脉冲Serrodyne非线性展宽与移频  

Ultrafast pulses Serrodyne nonlinear broadening and frequency shift in molecular alignment system

作　　者：刘大伟 杨光 罗代均 达娜·加山尔 范广宇 刘一[1] Liu Dawei;Yang Guang;Luo Daijun;Dana·Jiashaner;Fan Guangyu;Liu Yi(School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;Westlake Institute for Optoelectronics,Hangzhou 311421,China)

机构地区：[1]上海理工大学大学光电信息与计算机工程学院,上海200093 [2]西湖大学光电研究院,浙江杭州311421

出　　处：《红外与激光工程》2024年第5期64-72,共9页Infrared and Laser Engineering

基　　金：国家自然科学基金项目(12374318)。

摘　　要：超快光学的发展推动了光-物质相互作用研究进入了强场、高能的极端光学条件。然而,许多创新和应用需要专用的激光参数,包括波长、强度、脉冲长度、重复频率等。尤其是波长,这是一个非常重要但调控不太灵活的参数。报告了分子准直效应导致的超快脉冲的Serrodyne非线性展宽与频率转换,实现了对光波长的精确移频。通过研究脉冲形状与瞬态频率的关系,解析了Serrodyne效应在引发非线性动力学过程中的作用机制。与克尔非线性不同,在分子准直体系下,光谱移频的大小受分子响应时间和脉宽的共同影响,为在超快光源调控中引入新的自由度提供了可能性。Objective The advancement in ultrafast optics has propelled research on light-matter interactions into extreme optical conditions characterized by strong fields and high energies.However,many innovations and applications demand specialized laser parameters,including wavelength,intensity,pulse duration,and repetition rate.Particularly,wavelength is a crucial yet less flexible parameter to control.This paper reports the Serrodyne nonlinear broadening and frequency conversion induced by the molecular alignment effect in ultrafast pulses,achieving precise wavelength shifting.By investigating the relationship between pulse shape and transient frequency,we elucidate the mechanism of the Serrodyne effect in triggering nonlinear dynamical processes.Unlike Kerr nonlinearity,in the molecular alignment system,the magnitude of spectral shift is influenced by both the molecular response time and pulse width,providing possibilities for introducing new degrees of freedom in the control of ultrafast light sources.Methods In our study,we employ numerical simulations to introduce the Serrodyne effect into the Kerr system and achieve molecular alignment through the nonlinear Schrödinger propagation equation.Our objective is to establish the relationship between the shape and direction of the sawtooth pulse and the spectral frequency shift of the pulse.The nonlinear propagation dynamical induced by the Serrodyne effect are elucidated by mapping the transient frequency in relation to the pulse shape in the time domain.To comprehensively explore this effect,we adopt two approaches.Firstly,we maintain the steepness of the sawtooth-shaped pulse constant while adjusting the pulse width by varying t_(1)and t_(2)in equal proportions.This approach enables a systematic investigation into the effect of pulse width with a fixed shape pulse.Secondly,we vary the steepness of the pulse by adjusting the ratio of t_(1)and t_(2),denoted as Ri(Ri=t_(2)/t_(1)),allowing us to explore the impact of changes in steepness.Results and Discussions Figure 1

关 键 词：Serrodyne效应 自相位调制 分子准直 瞬态频率 

分 类 号：O437.3[机械工程—光学工程]