Theory and simulations of tunable two-mirror and three-mirror resonant-cavity photodetectors with a built-in liquid-crystal layer

Integrated, tunable resonant-cavity photodetectors with a built-in liquid-crystal layer structure are described. Two structures, a single resonant-cavity (Fabry-Perot) configuration and a three-mirror resonant-cavity configuration, are investigated theoretically. A quantum efficiency formula for the three-mirror resonant-cavity configuration is derived and performance simulations and optimization for both configurations are presented. Additionally, a new performance measure referred to as the efficiency-linewidth joint criterion (ELJC) is defined for reasonable and convenient performance estimations. It is shown that a wide wavelength tuning range can be easily achieved for both configurations. Although it is hard to obtain a linewidth as narrow as 2 nm for the single resonant-cavity configuration, the three-mirror resonant-cavity configuration can achieve narrower linewidth and high quantum efficiency when optimized. This type of device may prove useful for wavelength division multiplexing (WDM) applications