Optical Gas Sensing Based on Free Carrier Absorption in Metal Oxides

Many semiconducting metal oxides have found applications in resistive type gas sensors [1] based on the change of their electrical properties induced by the gas reactions. Theoretically, the microscopic electrical properties of a metal oxide are correlated to its macroscopic optical properties such as refractive index [2]. The fundamental idea of this study is to reveal this relationship during gas sensing, which enables us to remotely readout the gas responses via optical signals instead of the conventional electrical signals.