Toluene optical fibre sensor based on air microcavity in PDMS

We prepared and demonstrated a compact, simple-to-fabricate, air microcavity in polydimethylsiloxane (PDMS) placed at the end of a single-mode optical fibre. This microcavity creates a Fabry-Perot interferometer sensor able to measure concentrations of toluene vapour in air. Operation of the sensor is provided by diffusion of the toluene vapour to the PDMS, and the consequent extension of length d of the air microcavity in PDMS. The sensor response for the presence of vapours is fast and occurs within a few seconds. By using the prepared sensor toluene vapour concentration in air can be measured in the range from about 0.833 g.m−3 to saturation, with better sensitivity than 0.15 nm/g.m−3 up to maximal sensitivity 1.4 nm/g.m−3 at around concentration 100 g.m−3 in time 5 s.