The missing link between standing- and traveling-wave resonators

TL;DR

This paper introduces a novel class of photonic resonators supporting hybrid modes that combine standing- and traveling-wave characteristics within a single structure, bridging the traditional classification gap.

Contribution

It presents a new type of resonator supporting modes with location-dependent standing- and traveling-wave properties, expanding the understanding of optical resonator modes.

Findings

Demonstration of hybrid optical modes with spatially varying wave characteristics

The concept is applicable to chip-scale photonics and free-space optics

Potential extension to microwaves and acoustics

Abstract

Optical resonators are structures that utilize wave interference and feedback to confine light in all three dimensions. Depending on the feedback mechanism, resonators can support either standing- or traveling-wave modes. Over the years, the distinction between these two different types of modes has become so prevalent that nowadays it is one of the main characteristics for classifying optical resonators. Here, we show that an intermediate link between these two rather different groups exists. In particular, we introduce a new class of photonic resonators that supports a hybrid optical mode, i.e. at one location along the resonator the electromagnetic fields associated with the mode feature a purely standing-wave pattern, while at a different location, the fields of the same mode represent a pure traveling wave. The proposed concept is general and can be implemented using chip-scale photonics as well as free-space optics. Moreover, it can be extended to other wave phenomena such as microwaves and acoustics.