Intermodal strong coupling and wideband, low-loss isolation in silicon

TL;DR

This paper demonstrates wideband strong coupling between photonic bands in silicon, enabling low-loss optical modulation and isolation through electrically driven phonons, expanding integrated photonics capabilities.

Contribution

It introduces a novel wideband strong coupling mechanism in silicon using electrically driven phonons, unlike traditional narrow-linewidth resonator approaches.

Findings

Achieved strong coupling with Rabi-like energy exchange.

Demonstrated a low-loss acousto-optic modulator with >55 dB pump suppression.

Realized a broadband optical isolator with 59 GHz bandwidth.

Abstract

Strong coupling enables a diverse set of applications that include optical memories, non-magnetic isolators, photonic state manipulation, and signal processing. To date, strong coupling in integrated platforms has been realized using narrow-linewidth high-Q optical resonators. In contrast, here we demonstrate wideband strong coupling between two photonic bands. The indirect interband photonic transition is controlled by electrically driving phonons in a linear silicon waveguide. Under large acoustic drive, the system features a Rabi-like energy exchange between two waveguide modes, demonstrating strong coupling. When tuned to unity energy conversion, our system unlocks a set of powerful applications, including optical modulators, routers and filters. In particular, we demonstrate a low loss (-2.08 dB) acousto-optic modulator (AOM) with pump suppression ratio > 55 dB. We also reconfigure our system to demonstrate a non-magnetic, low-loss (< 1 dB) and broadband (59 GHz 10 dB isolation bandwidth) optical isolator.