Optimising porous silicon Bragg reflectors for narrow spectral resonances

摘要

Achieving sharp spectral resonances in porous silicon based photonic structures is of significant practical importance for improving the accuracy of refractive index-based sensing in chemical and biochemical applications. Here, we show that by compensating for depth related heterogeneities in the etching conditions, we are able to reduce the porosity modulation in Bragg reflectors to below 1% and achieve absorption limited spectral widths of 7 nm in the visible part of the spectrum. Such narrowband Bragg reflectors provide markedly improved sensing capability for real-time monitoring of refractive index changes compared with reflectors with broader spectral features. Published by AIP Publishing.