Detection of propane gas adsorbed in a nanometer layer on silica nanowire

In the present work, a miniature optical gas sensor for the leakage detection of propane is proposed. It is constructed by employing single mode silica nanowire Mach-Zehnder interferometer (MZI). Suitable chemical treatment of silica nanowire for propane gas adsorption onto it is suggested. In the proposed sensor, the idea is that, the propane gas gets adsorbed on treated surface of silica nanowire, which changes the refractive index of few nanometer thick layer on the nanowire surface. In theoretical modeling and simulation, full vectorial analysis of two and three layers tightly guiding waveguide structures are presented. Simulations include calculation of phase difference at the output end of MZI, phase sensitivity, detection limit and measurable refractive index over a practicable sensing length such as 1 mm. Sensing characteristics are numerically investigated. The sensor shows merits over conventional gas sensors. The sensing characteristics show negligible dependence on temperature, vibration and humidity, which is discussed in details. The proposed gas sensor is featured by high sensitivity, low cost, low loss, miniaturize size, and shows possibility of early detection of leakage.