Near-Zero Index Photonic Crystals with Directive Bound States in the Continuum

TL;DR

This paper introduces a novel all-dielectric photonic crystal design that supports near-zero-index modes coupled with directive bound states in the continuum, significantly reducing radiative losses and enhancing light manipulation capabilities in nanophotonics.

Contribution

The work presents a new photonic crystal structure that achieves near-zero index modes with directive bound states in the continuum, overcoming previous loss and radiation limitations.

Findings

Supports near-zero-index electromagnetic modes

Achieves directive bound states in the continuum

Reduces radiative losses in photonic crystals

Abstract

Near-zero-index platforms arise as a new opportunity for light manipulation with boosting of optical nonlinearities, transmission properties in waveguides and constant phase distribution. In addition, they represent a solution to impedance mismatch faced in photonic circuitry offering several applications in quantum photonics, communication and sensing. However, their realization is limited to availability of materials that could exhibit such low-index. For materials used in the visible and near-infrared wavelengths, the intrinsic losses annihilate most of near-zero index properties. The design of all-dielectric photonic crystals with specific electromagnetic modes overcame the issue of intrinsic losses while showing effective mode index near-zero. Nonetheless, these modes strongly radiate to the surrounding environment, greatly limiting the devices applications. Here, we explore a novel all-dielectric photonic crystal structure that is able to sustain effective near-zero-index modes coupled to directive bound-states in the continuum in order to decrease radiative losses, opening extraordinary opportunities for radiation manipulation in nanophotonic circuits. Moreover, its relatively simple design and phase stability facilitates integration and reproducibility with other photonic components.