Optical properties of opaline photonic crystals covered by phase-change material Ge$_2$Sb$_2$Te$_5$

TL;DR

This paper investigates the origin of Wood's anomalies in the reflection spectra of 3D opaline photonic crystals covered with GST225, revealing they stem from quasiguided modes in the capping layer through combined experimental and theoretical analysis.

Contribution

It provides a detailed eigenmode analysis showing that Wood's anomalies originate from quasiguided modes in the GST225 layer, supported by experimental and Fourier modal method simulations.

Findings

Resonant Wood's anomalies are caused by quasiguided modes in the GST225 layer.

Experimental spectra agree well with theoretical Fourier modal method calculations.

Eigenmode analysis clarifies the physical origin of anomalies in the studied structure.

Abstract

The physical origin of resonant Wood's anomalies in the reflection spectra of three-dimensional (3D) opaline photonic crystals covered with Ge$_2$Sb$_2$Te$_5$ (GST225) is discussed. For this purpose, the optical reflection spectra are studied for different incident angles of light both experimentally and theoretically. The performed eigenmode analysis reveals that the Wood's anomalies originate from the quasiguided modes which appear in the GST225 capping layer. This conclusion is supported by the simulated electromagnetic near-field distributions of incident light at resonant frequencies. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.