Band structure and optical properties of opal photonic crystals

TL;DR

This paper presents a theoretical method to interpret the reflectance spectra of opal photonic crystals, distinguishing between different diffraction mechanisms and validating the approach with experimental measurements.

Contribution

It introduces a theoretical framework based on photonic band calculations to analyze reflectance spectra of fcc opal photonic crystals and correlates it with experimental data.

Findings

Clear distinction between diffraction by (111) planes and higher-order planes.

Experimental evidence of diffraction by higher-order crystalline planes.

Theoretical interpretation aligns with reflectance measurements.

Abstract

A theoretical approach for the interpretation of reflectance spectra of opal photonic crystals with fcc structure and (111) surface orientation is presented. It is based on the calculation of photonic bands and density of states corresponding to a specified angle of incidence in air. The results yield a clear distinction between diffraction in the direction of light propagation by (111) family planes (leading to the formation of a stop band) and diffraction in other directions by higher-order planes (corresponding to the excitation of photonic modes in the crystal). Reflectance measurements on artificial opals made of self-assembled polystyrene spheres are analyzed according to the theoretical scheme and give evidence of diffraction by higher-order crystalline planes in the photonic structure.