Unidirectional Photonic Circuit with Phase-Change Fano Resonator

TL;DR

This paper presents a photonic circuit integrating a phase-change material to achieve unidirectional Fano resonances and transmission, enabling potential on-chip isolators and Q-switches with direction-dependent behavior.

Contribution

The study introduces a novel unidirectional photonic circuit using phase-change materials to control light transmission based on input direction.

Findings

Unidirectional Fano resonances observed in the circuit.

Transmission window depends on input light direction.

Phase change triggered by light-induced heating affects transmission.

Abstract

We demonstrate that the integration of a phase-change material (PCM) in one of the two microresonators of a photonic metamolecule, coupled to a bus waveguide, can lead to unidirectional Fano resonances and to the emergence of a unidirectional transmission window. The phase change is caused by light-induced heating and is accompanied by an abrupt increase in the extinction coefficient of the PCM resonator. Due to the photonic circuit asymmetry, the critical value of the input light intensity triggering the phase change is strongly dependent on the input light direction. The latter determines the unidirectional nature of the emerging transmission window. This effect can be utilized in on-chip magnetic-free isolators and Q-switches.