Ultra-broadband surface-normal coherent optical receiver with nanometallic polarizers

TL;DR

This paper introduces a compact, surface-normal coherent optical receiver with nanometallic polarizers that achieves high-speed demodulation over a broad wavelength range, overcoming limitations of traditional waveguide-based systems.

Contribution

It presents the first surface-normal homodyne optical receiver with integrated nanometallic polarizers, enabling ultra-broadband operation and scalable high-speed coherent detection.

Findings

Demonstrated high-speed (up to 64 Gbaud) coherent signal demodulation.

Achieved ultra-broadband operation from 1260 nm to 1630 nm.

Device footprint is only 70 μm square.

Abstract

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