Near-zero-index waveguide for beam steering

TL;DR

This paper introduces a simple, general method for creating near-zero index waveguides in dielectric materials, enabling broadband and narrowband NZI behavior and demonstrating beam steering with wide angular range for advanced photonic applications.

Contribution

A new approach for realizing NZI in dielectric waveguides independent of Dirac-like modes, applicable to various materials and bandwidths, enhancing photonic circuit design.

Findings

Achieved 140 nm broadband NZI in Si3N4 waveguides.

Demonstrated beam steering with 105-degree range.

Compared to prior work, bandwidth is doubled.

Abstract

Zero-index materials (ZIMs) have become popular because of their unique optical behaviors, such as infinite effective wavelengths and spatially uniform electromagnetic distributions. The all-dielectric ZIMs, Dirac-like cone-based zero-index materials (DCZIMs) are used in various photonic applications owing to their superior optical properties, such as finite impedances, zero Ohmic losses, and high compatibility with photonic circuits. We propose a more general and simple approach that is independent of the Dirac-like cone mode for realizing near-zero index (NZI) behavior in all-dielectric waveguides. This approach can be applied to various dielectric materials up to the necessary NZI bandwidth. Si3N4 and Ge NZI waveguides are demonstrated for achieving broadband and narrowband NZI, respectively. The proposed broadband NZI waveguide achieves a bandwidth of 140 nm for neff < 0.1 (neff = effective refractive index) at telecommunication wavelengths, which is 2 times larger than that of the reported NZI waveguides. Further, NZI waveguide-based beam steering was demonstrated with a wide steering range delta theta 105 degrees across the radiation angle of theta 0 degree. The proposed NZI-waveguide design principle and beam steering present a feasible approach for the development of photonic circuits and zero-index-based photonic applications.