摘要
基于光电流模型,通过数值模拟和理论分析,研究了静电场幅值对飞秒激光气体微等离子体中太赫兹辐射的影响。结果显示,随着外加静电场幅值的增大,太赫兹辐射的强度呈线性增大;当外加电场极性相反时,太赫兹波形整体反转;当外加电场与线偏振激发激光的偏振方向呈一定夹角时,太赫兹辐射的偏振方向完全由外加电场方向决定。数值模拟结果与已有的实验结果相符。理论分析表明,这个线性依赖、极性反转以及夹角依赖均源于等离子体产生之后的静电加速的主导作用。
Objective Terahertz(THz)radiation has attracted significant attention and gained wide applications in biology,imaging,sensing,and communications due to its unique characteristics.Femtosecond laser filamentation is one of the important approaches to obtain THz pulses with ultra-broad bandwidth and high electric field.With the rapid development of femtosecond laser technology,plasma based THz generation by a femtosecond laser has been well studied,in which two theoretical models are generally adopted for understanding the physical mechanism of THz radiation generation,namely the photocurrent model and the four wave mixing model,respectively.By applying an external direct-current(DC)electric field to the laser-induced plasmas filament,the enhancement of THz radiation by several orders of magnitude has been reported.However,the physical mechanism of laser-induced THz emission enhancement under the aid of an external DC electric field remains unclear because of the complicated laser-plasmas interaction process.In this paper,based on the photocurrent model,we analyze and numerically investigate the performance of THz radiation from a direct-current electric field biased single-color femtosecond laser ionized gas micro-plasma.The results show that the photocurrent model is effective in interpreting the THz generation of DC-biased laser-induced gas plasmas.Methods The photocurrent model attributes the THz radiation to a quasi-DC electron current produced by electron motion in the laser field.In this work,the THz generation from an 800nm femtosecond laser-induced plasma in Argas is investigated.First,we calculate the ionization rate of Ar-gas interacting with a laser by using the ADK formula,and the density of ionized electron can be obtained by an equation[Eq.(5)].Second,the initial velocities of the ionized electrons are assumed to be zero,which are then accelerated by field.By making use of Newton’s second law,the transient velocity of electron motion is derived.If the electron density and velocity are given,the elec
作者
王依海
龙娟
刘呈普
王铁军
高欣
Wang Yihai;Long Juan;Liu Chengpu;Wang Tiejun;Gao Xin(College of Physics,Guizhou University,Guiyang 550025,Guizhou,China;State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-Intense Laser Science,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《中国激光》
EI
CAS
CSCD
北大核心
2022年第11期197-204,共8页
Chinese Journal of Lasers
基金
国家自然科学基金(11965007,12074398)
NSAF联合基金(U2130123)
中国科学院战略性先导科技专项(B类)(XDB160104)
中国科学院国际合作重点项目(181231KYSB20200033)
上海市科技计划项目(21511105000)。
关键词
激光光学
超快激光
激光成丝
太赫兹辐射
静电场
数值模拟
laser optics
ultrafast laser
laser filamentation
terahertz radiation
static electric field
numerical simulation
