Theoretical Study of Optical Rectification at Radio Frequencies in a Slot Waveguide

We present a theoretical study of optical rectification (OR) at radio frequencies (RF). OR is a process by which a second-order nonlinear optical material can directly convert an optical field into an RF electric field. The combination of high-index nanoscale waveguides and new optical materials allow this effect to be greatly enhanced. We develop a lumped-element equivalent circuit model for the OR process from first principles, which enables the power conversion and bandwidth of the effect to be predicted. We use our model to predict that significant amounts of RF power should be obtainable from a slot waveguide device clad in a nonlinear optical polymer. Based on our model, we estimate that OR-based photodetectors may be possible, operating at speeds of 400 GHz, with responsivities on the order of 9 mA/W.