High-Field Coherent Terahertz Radiation Generation From Chirped Laser Pulse Interaction With Plasmas

Abstract

This article presents a theoretical analysis of high-field terahertz (THz) radiation generation from chirped laser pulse interaction with a plasma of slanting density modulation. The mechanism is based on strong nonlinear transverse current produced by the beating of two chirped laser pulses, where the plasma density modulation is inclined at angle to the propagation of the lasers. We claim that oblique spatial density ripple plays a crucial role in field enhancement of THz. At resonance (due to the phase-matching), the field strength of THz becomes maximum for a particular slating angle of the plasma density modulation. We claim that the oblique spatial density ripple and laser frequency-chirp combinedly play a crucial role in field enhancement of THz field. We observe that stable THz is generated with a maximum field strength of 100 MV/cm and a relatively broad spectrum extending out to 2.4 THz, with a strong dependence on the selection of slating angle of plasma density ripple and laser frequency chirp parameter, which corresponds to the conversion efficiency in order of 10 −2. The efficiency of the process may be optimized and controlled by the laser and plasma parameters, which may be useful in various applications of these kind of high-field THz.

Terahertz tuning by core-shell nanoparticles irradiated by skew-cosh Gaussian lasers

“…Gurjar et al have investigated the generation of THz radiation via interaction of pulsed laser with electron-hole plasmas [13]. The interaction of chirped laser pulses with plasma results in the generation of highly coherent THz radiation [14]. The role of density ripples related to plasma channels and external magnetic field for stronger excitation of THz field has also been evaluated [15][16][17][18][19][20].…”

Laser chirp controlled relativistic few-cycle mid-infrared pulse generation

“…Frequency chirp widely exists in femtosecond (fs) lasers, which can be produced easily by adjusting the grating spacing of the compressor in experiments. Chirped laser pulses (CLPs) have also been widely applied in laser-plasma interaction, such as improving the quality of electron beams [39][40][41][42] , enhancing the radiation intensity of THz emission [43][44][45] and HHG [46,47] . In the nonlinear case, compared with un-chirped laser pulses, the negatively chirped laser pulses (NCLPs) are compressed longitudinally in plasma, while the positively chirped laser pulses (PCLPs) can be stretched [40] .…”

Laser intensity profile based terahertz field enhancement from a mixture of nano-particles embedded in a gas

“…Laser-plasma interaction can produce highly energetic and ultra-short THz fields. Laser-plasma based methods (Varshney et al 2015 ; Varshney et al 2018 ; Cho et al 2015 ; Gurjar et al 2020 ; Singh and Sharma 2013 ) have been used for high power THz emission in past few years as plasmas have no damage threshold limit. As laser technology progresses for higher peak intensities (Strickland and Mourou 1985 ), THz peak power can be increased by scaling up the laser intensity.…”