Optical surface edge Bloch modes: low-loss subwavelength-scale 2D light localization

TL;DR

This paper reports on the discovery and analysis of low-loss, subwavelength-scale 2D light localization modes at the edges of finite-size woodpile photonic crystals, with potential applications in integrated photonics.

Contribution

It introduces the concept of optical surface edge Bloch modes in non-metallic materials and analyzes their properties and coupling behavior.

Findings

Mode area as small as 0.066 λ²

Propagation loss is small

Field maxima occur at dielectric-vacuum interface

Abstract

Edge modes of a finite-size woodpile can appear within a complete bandgap on an <010> edge. The mode area is as small as 0.066 squared half-in-vacuum-wavelengths, and the propagation loss is small. The field maxima occur at a dielectric-vacuum interface, like at a metal-dielectric interface for surface plasmon modes. The edge mode is a subwavelength-scale 2D light localization mode in non-metallic materials. Analysis of two-mode co-directional coupling between identical surface Bloch modes suggests that a large photonic crystal or surface designing would be needed for suppressing the evanescent field coupling in the woodpile.