Grant: Discovery Grants Program - Individual

Climate change and its consequences are one of the most important issues humanity will have to face in the coming decades. Reliable modeling can only come from an accurate knowledge of the composition of the atmosphere. This program is aimed at the development of a powerful in-situ instrument to detect pollutants in the atmosphere using a variant of tunable diode laser absorption spectroscopy. The miniature dimension of the instrument will allow an easy deployment on small balloon payloads or aircrafts for atmospheric measurement campaigns. Additionally, this new instrument will find many applications in industry (e.g., leak detection, process control systems, etc), in agriculture (e.g., emission from soils, livestock, etc) and in forensic science (e.g., detection of explosives, narcotics and other chemical substances, etc). Standard in-situ technique consists of a set of tunable diode lasers, an absorbing medium and a detector. When the laser frequency is tuned over the absorption lines of a gas, a part of the laser intensity is lost when the laser beam passes through the gas. The remaining intensity is measured by the detector at the exit of the absorbing medium and analyzed to obtain the concentration, temperature and velocity of the gaz. Despite its great sensitivity, the deployment of this technique for atmospheric measurements has been limited because it requires a long path length through heavy multi-pass cell. My plan is to use a new spectroscopic technique based on the whispering-gallery modes (WGMs) of silica micro-resonators to develop a portable sensitive infrared spectrometer for in-situ detection of trace gases. The WGMs are resonance modes in which light is confined, by internal reflection, at the surface of a circular micro-resonator. When the resonator is set inside a gas vapour and its WGM tuned over an absorption frequency of the gas, an energy loss occurs by a non-radiative transfer between the resonator and the neighbouring molecules. As this non-radiative transfer rate is considerably higher than the radiative absorption rate, we can obtain, by analyzing the energy loss, a sensitivity equivalent to those obtained by a bulk device.