Analysis and Design of Photoconductive Antenna Using Spatially Dispersive Graphene Strips with Parallel-Plate Configuration

In this paper, a photoconductive antenna (PCA) is designed using spatially dispersive graphene strips (GSs) with parallel-plate configuration. This configuration maintains the properties of a single GS and at the same time provides more tunability for designing a graphene-based PCA (GPCA). When a GS is surrounded by a high-index media, propagating wave vector along the structure becomes spatially dispersive, because the group velocity of the propagating wave is greatly reduced and it becomes comparable to Fermi velocity in graphene. In this situation, it is necessary to use a nonlocal conductivity model for graphene. In this paper, a nonlocal per unit length circuit model is employed to study wave propagation in the GPCA. In the circuit model, the nonlocal behavior will be modeled via a per unit length quantum capacitance that under certain conditions it is simplified to quantum capacitance in graphene. In deep subwavelength regime, due to strong coupling between GSs in the the double stacked configuration, it can be replaced by a single GS that its conductivity is two times greater than the former case. Finally, the GPCA is fed by a wide-band photocurrent in order to terahertz radiation and detection are investigated.