High Optical Reflection in Two-dimensional ZnO-Si Photonic Crystals Induced by Coupled Optical Micro-cavities

Abstract

Photonic crystals can exhibit relevant optical properties when transmitting or reflecting a light beam. In particular in a two-dimensional photonic crystal the reflective properties can be of interest and consequently optimized for different technological applications such as tunable laser cavities, photovoltaic solar systems, and selective high reflection mirrors among many others. Taking this motivation into account, a study of the reflective optical properties of two-dimensional photonic crystals built on a hybrid substrate of ZnO:Si has been developed. The aim of the present research is to demonstrate the feasibility to control the optical reflectance spectra of a two-dimensional photonic crystal by the inclusion of an array of optical micro-cavities in a regular photonic structure. Moreover, in this research an explanation of the origin of the high optical reflectance predicted by numerical calculations and confirmed by experimental measurements in a photonic crystal that contains an array of micro-optical cavities is also given. The results of numerical calculations of the optical properties of one of the photonic crystals studied determined that the origin of the increase in its optical reflectance is the light emission from the silicon present in the ZnO-Si substrate where the photonic structure was built. Strong resonant modes of the optical electric field stablished mainly in silicon present in two types of resonant cavities recognized in the photonic crystal favor the stimulated emission of light that gives rise to the high optical reflectivity.