激光大气成丝中的非线性光频转换

超快强激光在光学介质（如空气）中传播时由于克尔自聚焦效应和等离体散焦效应动态平衡会发生一种独特的非线性激光成丝现象。激光成丝过程会诱导一些独特的物理现象，如非线性光频转换产生超连续光谱、等离子体诱导高压放电、锥形辐射等，在大气传感、天气控制等研究领域具有重要的应用前景。本文针对飞秒激光大气成丝过程中与传输介质相互作用所诱导的非线性发光过程，介绍了激光大气成丝所产生的超连续光谱（白光）激光、谐波产生和太赫兹波辐射三种非线性光频转换现象，并着重探讨了太赫兹波辐射的物理机理、研究现状和应用前景。

Nonlinear frequency conversion in laser lamentation in air

The propagation of ultrafast strong laser pulses in optical media (such as air) can produce a uniquenonlinear laser filamentation phenomenon due to the dynamical balance between the optical Kerrself-focusing and plasma defocusing effects. Laser filamentation can induce some unique physicalphenomena such as supercontinuum generation via nonlinear frequency conversion, plasmainducedhigh voltage discharge, and conical emission, which lead to its promising applicationsin areas such as atmospheric sensing, weather control. In this paper, we present an overview ofnonlinear radiation processes induced by the interaction of femtosecond laser pulses in the filamentationwith the propagation media. Three types of nonlinear frequency conversion phenomena,i.e., supercontinuum (white light), harmonic generation, and THz radiation, are introduced. Wethen give a detailed discussion about the physical mechanisms, current status, and promisingapplications of THz radiation.