Near-infrared Polarization-insensitive Photodetector Based on Plasmonic Cavity Enhanced Light Absorption

A polarization-insensitive plasmonic cavity photodetector is presented using a two-dimensional nanoscale gold cylindrical array as a plasma electrode. The two-dimensional symmetry of the cylinder makes the plasma electrode insensitive to the polarization angle of the incident light. By forming a metal-semiconductor-metal cavity between a subwavelength metal cylinder and a metal reflector, effective enhancement of light absorption in the ultrathin region can be achieved. The optical and electrical responses of the photodetector were calculated using the time-domain finite difference method and the finite element method, and the effects of the geometric parameters on the performance of the gold nanocylinders were analyzed. The results show that after optimizing the parameters, the overall light absorption rate of the device is 94.7%, and the light absorption rate in GaAs semiconductor can reach 81.1%, and the responsivity of the device can reach 0.37 A/W at 5 V bias voltage and 10 mW incident light power. The device exhibits extremely low polarization-dependent characteristics, where changes in polarization angle do not cause changes in absorption in the device semiconductor, and the absorption response can be effectively preserved without changes in the position of the absorption peak when the angle of incidence changes.