Hybrid graphene/silicon integrated optical isolators with photonic spin-orbit interaction

TL;DR

This paper proposes an ultracompact, graphene-based integrated optical isolator on silicon-on-insulator, achieving high isolation with a small footprint by exploiting photonic spin-orbit interaction and cavity resonance effects.

Contribution

It introduces a novel graphene/silicon integrated optical isolator leveraging photonic spin-orbit interaction for nonreciprocity, enabling CMOS-compatible, miniaturized devices.

Findings

Extinction ratio over 45 dB

Insertion loss around 12 dB

Device optimized near 1.55 μm wavelength

Abstract

Optical isolators are an important building block in photonic computation and communication. In traditional optics, isolators are realized with magneto-optical garnets. However, it remains challenging to incorporate such materials on an integrated platform because of the difficulty in material growth and bulky device footprint. Here, we propose an ultracompact integrated isolator by exploiting graphene's magneto-optical property on a silicon-on-insulator platform. The photonic nonreciprocity is achieved because the cyclotrons in graphene experiencing different optical spin exhibit different response to counterpropagating light. Taking advantage of cavity resonance effects, we have numerically optimized a device design, which shows excellent isolation performance with the extinction ratio over 45 dB and the insertion loss around 12 dB at a wavelength near 1.55 um. Featuring graphene's CMOS compatibility and substantially reduced device footprint, our proposal sheds light to monolithic integration of nonreciprocal photonic devices.