Enhanced sensitivity and response speed in surface-normal InGaAs photodetectors with Au grating through waveguide-plasmon coupling

We proposed the improvement of near-infrared (NIR) sensitivity and response speed for surface-normal photodetector by coupling the surface plasmon (SP) mode excited at the plasmonic grating to the waveguide (WG) mode in the absorption layer. The thinner absorption layer accelerated response speed. The absorption efficiency in the InGaAs thickness of 300 nm was significantly improved to 51.4% at the wavelength of 1550 nm under the wave vectors matching between SP mode and WG mode. Moreover, the one-dimensional line and space plasmonic grating exhibited high polarization selectivity. Polarized light discrimination is applied to a multi-valued modulation scheme for multiplexing signal channels. The enhancement of NIR sensitivity and response speed by the proposed mode coupling is useful for the two-dimensional (2D) integration of surface-normal photodetectors by increasing the spatial signal channels and can contribute to the data capacity expansion in next-generation optical communication systems.