Effect of laser intensity redistribution on semiconductor plasma based THz emission

Abstract

THz emission has been investigated using laser beat wave interaction with density rippled semiconductor plasmas. Two lasers with frequency ω1 and ω2 co-propagate through density rippled semiconductor plasma having wave vector α and beat laser wave imparts ponderomotive force on electrons that produce nonlinear current and allows the THz emission. Gaussian, ring shape and hollow Gaussian field envelopes have been considered introducing laser intensity distribution along the polarization direction. Redistribution of laser intensity due to varied spatial profile changes the dynamics of plasma electrons and improves the ponderomotive force. Enhancement in the doping level in semiconductor also acts as a tuning parameter for the THz emission. Combined effect of laser intensity redistribution and amplitude of density modulation (nα/n0) enhances the amplitude of the THz field. Conversion Efficiency of the order ≈ 10−6 is estimated for hollow Gaussian field envelope and density modulation of 20% in semiconductor plasma.