Optical humidity sensing and ultrasound effect for mesoporous silicon one-dimensional photonic crystals.

Mesoporous silicon (PSi) microcavities (MC) based on one-dimensional photonic crystals have been studied as optical sensors for relative humidity (RH). Oxidized PSi modified the structure of the MC such that the spectral position of the MC resonance peak depended on the humidity. A spectral shift of the MC resonance peak of up to 6 nm to longer wavelengths was observed as the RH increased from 20% to 85%. Ultrasound affects the MC peak spectral position in the reverse direction as a result of water removal from mesoporous structure. This effect can be used for the stabilization of the peak spectral position for an optical interconnect and fast recovery of the optical gas sensors.