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Modeling of Evanescent Field Propane Gas Sensor Using Silane-Treated Single Mode Silica Nanowire

In the present work, two types of miniature propane gas sensors using silica nanowire are modeled and simulated. Silica nanowires leave large amount of guided field outside the core as evanescent field, which is sensitive to cladding refractive index and hence utilized for sensing purpose. In this paper, two types of sensors are investigated from silica nanowire waveguiding properties In both models, silica nanowire initially has air as cladding which changes to gaseous layer of propane when exposed to the propane gas. Layer formation is achieved by adsorption. Silica nanowire treated with methyl-hydrogen silane is used in these models to increase adsorption tendency of propane on the silica nanowire surface. In the first model, Mach-Zehnder interferometer is used for measurements. In the second model, measurements are carried out with photodetector-comparator circuit. High sensitivity conditions are obtained in both models. Simulation of the models show that using nanowires diameters of 350nm-750nm, high sensitivity can be achieved, even with small sensing length in the first model, whereas in the second model, high photocurrent can be obtained by using 650nm-950nm nanowire diameters. These sensors can be helpful in early detection of hazardous liquefied petroleum gas leakage.