Generation of terahertz radiation by large-aperture photoconductive antennas

Employing self-consistent analytical approach to the set of non-equilibrium Boltzmann equation and Maxwell equations we have studied the radiation phenomena in non-equilibrium e-h plasma excited in the photo-conductive gap of terahertz radiating antenna by an ultra-short laser pulse. The solutions of the radiation problem have established the fundamental role of retardation and non-stationary character of electromagnetic interaction of photo-currents of moving e-h plasma in the formation of radiation field. The revealed properties of generated terahertz pulse are crucially depend on the physics of dissipation mechanisms, the ratio of terahertz radiation formation length and sample size, current configurations and relative traveling velocities of e-h plasma bunch and terahertz radiation pulse. We have 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-h plasma related to the front and rare boundaries of semiconducting slab respectively.