Photoconductive devices (PCDs) enhanced with nanostructures have shown a significantly improved optical-to-terahertz conversion efficiency. While the experimental research on the development of such devices has progressed remarkably, simulation of these devices is still challenging due to the high computational cost resulting from modeling and discretization of complicated physical processes and intricate  geometries. In this work, a discontinuous Galerkin (DG) method-based unit-cell scheme for efficient simulation of PCDs with periodic nanostructures is proposed. The scheme considers two physical stages of the device and model them using two coupled systems, i.e., a Poisson-drift-diffusion (DD) system describing the nonequilibrium steady state, and a Maxwell-DD system describing the transient stage. A "potential-drop" boundary condition is enforced on the opposing boundaries of the unit cell to mimic the effect of the bias voltage. Periodic boundary conditions are used for carrier densities and electromagnetic fields. The unit-cell model composed of these coupled equations and boundary conditions is discretized and solved using DG methods. The boundary conditions are enforced weakly through the numerical flux of DG. Numerical results show that the proposed DG-based unit-cell scheme models the device accurately but is significantly faster than the DG scheme that takes into account the whole device  .
Photoconductive devices (PCDs) enhanced with nanostructures have a significantly improved optical-to-terahertz conversion efficiency. While the experimental research on the development of these devices has progressed remarkably, their simulation is still challenging due to the need for accurate and efficient modeling of multiphysics processes and intricate device geometries. In this work, a discontinuous Galerkin (DG) method-based unit-cell scheme for efficient simulation of PCDs with periodic nanostructures is proposed. The scheme considers two physical stages of the device and models them using two coupled systems, i.e., a system of Poisson and drift-diffusion equations describing the nonequilibrium steady state, and a system of Maxwell and drift-diffusion equations describing the transient stage. A "potential-drop" boundary condition is enforced on the opposing boundaries of the unit cell to mimic the effect of the bias voltage. Periodic boundary conditions are used for carrier densities and electromagnetic fields. The unit-cell model described by these coupled equations and boundary conditions is discretized using DG methods. The resulting DG-based unit-cell scheme is significantly faster than the DG scheme that takes into account the whole device . Additionally, the proposed scheme is used for the first-ever numerical demonstration of optical- and radiation-field screening effects on PCD response. The optical-field screening is found to play a more dominant role in the saturation of PCD output at high levels of optical pump power .
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