THz emission characteristics dependence on gap spacing of biased photoconductive antennas

The terahertz emission experiments on the biased photoconductors fabricated with SI-GaAs were performed using single femtosecond pulses under the same excitation intensity. Measuring the ratio of the negative to positive peak for various gap spacing, we obtain a near linearly decreasing type of trend with increasing gap spacing. For explaining these observed behaviors, a theoretical model containing drift-diffusion and Poisson's equation is utilized.