A hybrid drift-diffusion-TLM analysis of traveling-wave photodetectors

An efficient hybrid method for numerical analysis of traveling-wave photodetectors (TWPDs) is presented. The method is a combination of two-dimensional semiconductor and three-dimensional full-wave electromagnetic (EM) simulators. The time-domain drift-diffusion method is used to determine the photogenerated currents at the cross section of the device. Those currents are then defined as sources in the EM analysis to calculate the microwave bandwidth and output current of the device. In the analysis, the effects of the carrier velocity and lifetime, optical power, bias voltage, velocity mismatch, and microwave loss are taken into account. The method is tested in case of GaAs and low-temperature-grown GaAs-based TWPDs. A very good agreement between the theoretical and experimental data is observed. It was also possible to predict the saturation behavior of the TWPD under high optical illumination due to the field screening effect.

I. Introduction

High-Speed and efficient photoreceivers are key components of modern ultrawide-band optical communication systems. Traveling-wave photodetectors (TWPDs) having broad bandwidth and high efficiency are excellent candidates for such applications. Furthermore, the high power-handling capability of TWPDs is very important in microwave fiber-optic links, especially since optical pre-amplification is utilized more widely. The high power-handling capability of TWPDs comes from the fact that their output saturation current can be made high by reducing the modal optical absorption constant or by achieving uniform photoabsorption [1].