DESIGN subwavelength gratings in resonant cavity enhanced (RCE) photodetectors

Two-dimensional subwavelength gratings (2D-SWGs) that consist of net-grid structure are studied by rigorous coupled-wave approach (RCWA) and finite-difference-time-domain (FDTD) method. 2D-SWGs can be designed as infrared reflectors whose reflectivity can reach 99.98% at 1.55µm while maintaining reflectivity higher than 99% across the 1.47–1.59µm wavelength range. We design these SWGs as the bottom mirrors in resonant cavity enhanced photodetectors (RCE-PDs) for optical communication system. Because SWGs can achieve high reflectivity as well as wide bandwidth, RCE PD's quantum efficiency is increased to 95.7% at 1.55µm and the device has a significant size reduction compared with using DBR bottom mirror.