Time-Resolved Spectroscopy of Ethanol Evaporation on Free-Standing Porous Silicon Photonic Microcavities

In this work, we have followed ethanol evaporation at two different concentrations (70% and 35%) using a fiber optic spectrometer and a screen capture application with a resolving capacity of 10 ms. Porous Silicon microcavities were fabricated by electrochemistry etching of crystalline silicon. The microcavities were designed to have a localized mode at 472 nm (blue band) and an extended mode at 750 nm (red band). Ethanol infiltration produces a redshift of approximately 17 nm. After a few minutes, a phase change from liquid to vapor occurs, and both modes shift back to the blue band. This process happens in a time window of only 60 ms.