ON THE SENSITIVITY OF POROUS SILICON DUAL-STACK RUGATE FILTERS TO LIQUID INFILTRATION

Photonic crystals made by nanostructured porous silicon are attractive structures for a wide variety of sensing applications, such as biological and chemical sensors. Nanostructured porous silicon rugate filters (PSRFs), which is a peculiar case of one-dimensional photonic crystals, have been demonstrated to have great potential both for biological and chemical sensing application [1]. Nonetheless aging problems over time of PSRF-based (bio)sensors have not been carefully addressed so far and limit their exploitation in real-word applications. In this work we fabricated a dual-stack PSRF, each stack featuring a different spatial period, and investigated sensitivity dependence of stacks with different periods on refractive index changes upon infiltration with different water/ethanol mixtures, both in as-prepared and oxidized samples, this latter simulating aging over time. In order to investigate the effect of spatial periodicity (P) on the sensitivity of PSRF, we fabricated a dual-stack porous silicon rugate filter.