Broadband on-chip optical non-reciprocity using phase modulators

TL;DR

This paper proposes a broadband, CMOS-compatible on-chip optical non-reciprocal device using cascaded phase modulators and delay lines, achieving high extinction ratios without resonant structures.

Contribution

It introduces a novel non-reciprocal photonic architecture based on phase modulators and delay lines that is broadband and compatible with standard silicon photonics.

Findings

Extinction ratio exceeds 20 dB.

Insertion loss is below -3 dB.

The scheme is fully broadband and does not rely on resonant structures.

Abstract

Breaking the reciprocity of light propagation in photonic integrated circuits (PIC) - especially in the CMOS-compatible silicon-on-insulator platform - is a topic of intense research. However, a practical solution for monolithic integrating of optical isolators and circulators remains elusive. Here, we propose and analyze a new non-reciprocal photonic architecture operating with standard single-mode waveguides (or optical fibers). Our design exploits cascaded phase modulators separated by optical delay lines and suitably driven by time shifted waveforms. Because it is based on fully balanced interferometers and does not involve resonant structures, our scheme is also intrinsically broadband. Using realistic parameters we calculate an extinction ratio superior to 20 dB and insertion loss below -3 dB.