A Global Approach for Modeling and Analysis of Edge-Coupled Traveling-Wave Terahertz Photoconductive Sources

In this paper, a global and geometry-independent approach is proposed for accurate analysis of edge-coupled continuous wave (CW) traveling-wave terahertz photomixer sources. All major physical phenomena involved in the operation of such devices are included in three interconnected solvers, which are combined as a unified analysis tool. A photonic solver is developed to find the optical intensity across the fast photoabsorbing region from which the carrier generation rate is determined. A semiconductor solver is used to study the charge carrier transport inside the photoconductive region through drift-diffusion model, and to predict the generated photocurrent with the beat frequency of two CW lasers. An electromagnetic solver is introduced to rigorously calculate the coupled terahertz signal into the guiding transmission line through a Lorentz reciprocity theorem. Theoretical formulation behind each solver is discussed in detail, and numerical results from each solver are presented. The proposed approach is a powerful tool for global optimization of the photoconductive sources, especially for maximizing the optical-to-terahertz power conversion.