Splitting of porous silicon microcavity mode due to the interaction with Si–H vibrations

A Fabry–Perot microcavity centred in the infrared around 2000–2200 cm−1 has been realised by controlling the current and the time of a steps anodization procedure of a p+ type silicon wafer in an electrochemical cell with a hydrofluoric acid solution. The interaction of the cavity mode, detectable as a sharp deep in the high reflectivity plateau, with the Si–H vibration modes gives rise to a splitting of the cavity mode dispersion curve (frequency vs wavevector) and to an enhancement of the infrared absorption of the Si–H bands. Both, the dispersion of the coupled modes (cavity/Si–H modes) and their infrared absorption enhancement have been studied.