Nonlocal Scattering Matrix Description of Anisotropic Polar Heterostructures

TL;DR

This paper develops a scattering matrix theory to accurately describe the nonlocal optical response of anisotropic polar dielectric heterostructures, enabling precise prediction of their optical properties for mid-infrared nanophotonics.

Contribution

It introduces a novel nonlocal scattering matrix formalism for anisotropic layered polar dielectrics, extending previous local models and providing a practical computational tool.

Findings

Demonstrates strong nonlocal tunability in AlN/GaN superlattices

Shows hybridization of photon and phonon modes affects optical response

Provides a numerical code for designing phonon-based optoelectronic devices

Abstract

Polar dielectrics are a promising platform for mid-infrared nanophotonics, allowing for nanoscale electromagnetic energy confinement in oscillations of the crystal lattice. We recently demonstrated that in nanoscopic polar systems a local description of the optical response fails, leading to erroneous predictions of modal frequencies and electromagnetic field enhancements. In this Paper we extend our previous work providing a scattering matrix theory of the nonlocal optical response of planar, anisotropic, layered polar dielectric heterostructures. The formalism we employ allows for the calculation of both reflection and transmission coefficients, and of the guided mode spectrum. We apply our theory to complex AlN/GaN superlattices, demonstrating the strong nonlocal tuneability of the optical response arising from hybridisation between photon and phonon modes. The numerical code underlying these calculations is provided in an online repository to serve as a tool for the design of phonon-based mid-infrared optoelectronic devices.