Optical isolators based on non-reciprocal four-wave mixing

TL;DR

This paper proposes a theoretical design for optical isolators using all-dielectric resonators that exploit non-reciprocal four-wave mixing to achieve unidirectional light propagation, suitable for integrated photonics.

Contribution

It introduces a novel non-magnetic, all-dielectric optical isolator mechanism based on intensity-dependent refractive index and four-wave mixing, with detailed theoretical analysis and specific device configurations.

Findings

The proposed mechanism breaks optical reciprocity via asymmetric four-wave mixing.

The device designs can be realized with current integrated photonics technology.

The isolation effect is explained through Bogoliubov dispersion analogy.

Abstract

In this work we propose and theoretically characterize optical isolators consisting of an all-dielectric and non-magnetic resonator featuring an intensity-dependent refractive index and a strong coherent field propagating in a single direction. Such devices can be straightforwardly realized in state-of-the-art integrated photonics platforms. The mechanism underlying optical isolation is based on the breaking of optical reciprocity induced by the asymmetric action of four-wave mixing processes coupling a strong propagating pump field with co-propagating signal/idler modes but not with reverse-propagating ones. Taking advantage of a close analogy with fluids of light, our proposed isolation mechanism is physically understood in terms of the Bogoliubov dispersion of collective excitations on top of the strong pump beam. A few most relevant set-ups realizing our proposal are specifically investigated, such as a coherently illuminated passive ring resonator and unidirectionally lasing ring or Taiji resonators.