飞秒激光成丝过程中的太赫兹波空间强束缚效应  

Strong Spatial Confinement of Terahertz Waves Along Laser Plasma Filaments

作　　者：赵佳宇 韩永鹏 朱非凡 郭兰军[2] 张逸竹 彭滟[1] 朱亦鸣[1] 刘伟伟[2] Zhao Jiayu;Han Yongpeng;Zhu Feifan;Guo Lanjun;Zhang Yizhu;Peng Yan;Zhu Yiming;Liu Weiwei(Terahertz Technology Innovation Research Institute,University of Shanghai for Science and Technology,Shanghai 200093,China;Institute of Modern Optics,Nankai University,Tianjin 300350,China;School of Precision Instrument and Opto-Electronics Engineering,Tianjin University,Tianjin 300072,China)

机构地区：[1]上海理工大学太赫兹技术创新研究院,上海200093 [2]南开大学现代光学研究所,天津300350 [3]天津大学精密仪器与光电子工程学院,天津300072

出　　处：《中国激光》2023年第17期129-138,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金(12061131010,12074198);上海市青年科技启明星计划(22QC1400300)。

摘　　要：飞秒激光成丝辐射太赫兹波兼具宽频带和高强度特性,其物理机制研究已成为近年来的前沿课题。在此领域,本课题组发现太赫兹波沿激光等离子体光丝被限制在亚波长空间尺度内进行传输,即“太赫兹波空间强束缚效应”,并据此提出了能够全面阐述太赫兹波辐射机理的三过程模型,为统一当前主流宏观与微观理论、化解相关文献中重要结论的矛盾奠定了基础。本文以太赫兹波空间强束缚效应为中心,综述了本课题组近年来的一系列研究工作,包括实验探测技术、物理机理解释及多项创新应用等,并对未来的工作进行了展望。Significance Femtosecond laser filamentation in air refers to the technical approach of using the femtosecond laser to ionize air near its focal point,forming a plasma channel(also known as the optical filament)that emits terahertz(THz)waves.Due to the remote generation of plasma filaments and the broadband and high intensity characteristics of the emitted THz waves,femtosecond laser filamentation overcomes water vapor absorption losses in free-space THz transmission;thus,it is advantageous for applications such as remote sensing and communication in THz band.Therefore,the study of physical mechanisms of THz wave radiation by femtosecond laser filaments has become an important branch of THz science.However,there currently remains controversy surrounding the mainstream models for THz wave generation,and important experimental observations such as THz polarization and angular dispersion distribution remain in disagreement.For example,the two mainstream models,i.e.,four-wave mixing(4WM)and photocurrent(PC),have fundamental differences:when the THz wave yield is significant,the former assumes a relative phase difference of 0 between the fundamental and second harmonic laser fields,while the latter assumes aπ/2 phase difference.Furthermore,regarding the dependence of the far-field divergence angle of THz waves on frequency,the mainstream viewpoint represented by the off-axis phase matching model suggests that only dual-color filaments longer than the dephasing length can radiate THz waves with high-frequency components distributed inside and low-frequency components distributed outside.However,this explanation fails to account for the similar radiation behavior observed in short filaments,and contradicts experimental findings in some literature,which report high-frequency outside,low-frequency inside,or frequencyindependent angular distribution.Progress These unresolved contradictions pose significant challenges in the study of THz wave radiation from dual-color filaments.The reason for these contradictions could be

关 键 词：物理光学 太赫兹波 飞秒激光成丝 空间束缚 物理机制 超分辨成像 

分 类 号：O436[机械工程—光学工程]