Ultra-Broadband Surface-Normal Coherent Optical Receiver with Nanometallic Polarizers

A coherent receiver that can demodulate high-speed in-phase and quadrature signals of light is an essential component for optical communication, interconnects, imaging, computing. Conventional waveguide-based receivers, however, exhibit large footprints, difficulty in coupling a number spatial channels efficiently, limited operating bandwidth imposed by the hybrid. Here, we present surface-normal with nanometallic-grating-based polarizers integrated directly on top photodetectors without need hybrid circuit. Using fabricated device active section occupying 70-{\mu}m-square footprint, demonstrate demodulation (up to 64 Gbaud) various formats. Moreover, ultra-broadband operation from 1260 nm 1630 demonstrated, thanks wavelength-insensitive nanometallic polarizers. To our knowledge, this first demonstration homodyne receiver, which easily be scaled compact two-dimensional arrayed receive highly parallelized signals.