Generation of coherent terahertz radiation in ultrafast laser-gas interactions

作者：Kim Ki Yong^*

来源：Physics of Plasmas, 2009, 16(5): 056706.

DOI：10.1063/1.3134422

• high-speed optical techniques
• ionisation
• laser beam effects
• optical focusing
• optical harmonic generation
• photoemission
• plasma light propagation
• plasma nonlinear processes
• plasma simulation
• plasma transport processes
• submillimetre wave generation
• tunnelling

The generation of intense terahertz radiation in ultrafast laser-gas interactions is studied on a basis of transient electron current model. When an ultrashort pulse laser's fundamental and its second harmonic fields are mixed to ionize a gas, a nonvanishing, directional photoelectron current can be produced, which simultaneously emits terahertz radiation in the far field. Here, the generation mechanism is examined with an analytic derivation and numerical simulations, in which tunneling ionization and subsequent electron motion in the combined laser field play a key role. In the simulations, three types of laser-gas interactions are considered: (i) mixing the fundamental and its second harmonic fields, (ii) mixing nonharmonic, two-color fields, and (iii) focusing single-color, few-cycle pulses. In these interactions, terahertz generation and other nonlinear effects driven by the transient current are investigated. In particular, anticorrelation between terahertz and second (or third) harmonic generation is observed and analyzed.

• 出版日期2009-5