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

• Published in: arXiv.org 2022-06
• Main Authors: Go Soma, Yanwachirakul, Warakorn, Miyazaki, Toshiki, Kato, Eisaku, Onodera, Bunta, Tanomura, Ryota, Fukui, Taichiro, Ishimura, Shota, Sugiyama, Masakazu, Nakano, Yoshiaki, Tanemura, Takuo
• Format: Article
• Language: English
• Subjects: Broadband; Coherence; Demodulation; Footprints; High speed; Hybrid circuits; Optical communication; Optical receivers; Polarizers; Quadratures; Waveguides
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2206.00839

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.