Generation of terahertz radiation by a moving bunch of nonequilibrium electron-hole plasma

Abstract

We report on properties of coherent radiation from nonequilibrium electron-hole $(e\text{\ensuremath{-}}h)$ plasma bunch excited by an ultrashort laser pulse crossing a semiconducting slab subject to transverse bias voltage. Self-consisted calculations of nonequilibrium Boltzmann and Maxwell equations have established the fundamental role of uniformly moving bunch of $e\text{\ensuremath{-}}h$ plasma in coherent generation of terahertz radiation. We have shown that predicted properties crucially depend on the physics of dissipation mechanisms, current configurations, and relative traveling velocities of $e\text{\ensuremath{-}}h$ plasma bunch and terahertz radiation pulse. It has distinguished two major regimes of terahertz emission, single pulse emission, and firing twinned pulses at the moments of creation and extinction of moving bunch of $e\text{\ensuremath{-}}h$ plasma related to the front and rare boundaries of semiconducting slab, respectively. The results of developed theory are applied to enhance the performance of photoconductive terahertz emitters.