Modeling terahertz radiation from a photoconducting structure

Accurate characterization of the electromagnetic radiation arising from photoconducting systems is discussed. A computational technique is presented which combines the finite-difference time domain (FDTD) method with a spatial transformation, the Kirchhoff surface integral formulation. The technique enables incorporation of any number of material parameters while accurately accounting for the potentially wide-band nature of the radiation in an efficient computational method. Results are presented demonstrating a more accurate portrait of the radiation arising from a photoconducting structure than has been previously reported. Based on the simulation results, a simple model incorporating equivalent dipole sources is developed. Good agreement is shown between simulation results and measurements of similar structures.