Optical Isolation based on Space-time Engineered Asymmetric Photonic Bandgaps

TL;DR

This paper introduces a novel, magnetless optical isolator using space-time engineered asymmetric photonic bandgaps, enabling high isolation levels in integrated photonic circuits with low modulation frequency.

Contribution

It demonstrates a new approach to optical isolation based on space-time modulation, compatible with integrated photonics and requiring low modulation frequencies.

Findings

High isolation levels achieved experimentally at microwave frequencies.

The method is magnetless and highly reflective/transparent depending on propagation direction.

Requires only low modulation frequency for effective operation.

Abstract

Nonreciprocal electromagnetic devices play an important role in modern optical and microwave technologies. Conventional methods for realizing such systems are incompatible with integrated circuits. With recent advances in integrated photonics, the need for efficient on-chip magnetless nonreciprocal devices is more urgent than ever. This paper leverages space-time engineered asymmetric photonic bandgaps to generate optical isolation. It is shown that a properly designed space-time modulated slab is highly reflective/transparent for opposite directions of propagation. The proposed method requires a low modulation frequency, is magnetless and can achieve very high isolation levels. Experimental proof of concept at microwave frequencies is provided.