Remote sensing of the atmosphere using ultrashort laser pulses

Theoretical and experimental studies were performed on the propagation of u ltrashort optical terawatt pulses through the atmosphere. Propagation simul ations of intense sub-picosecond pulses show that non-linear processes, suc h as white light generation, can be initiated at a chosen distance by selec ting an appropriate group velocity dispersion. With this technique, a white light continuum was generated in the atmosphere whose spectral distributio n was characterised in the visible and near infra-red. Applications of this novel light source for atmospheric remote sensing were investigated, combi ning lidar and time-resolved broadband absorption spectroscopy techniques. Measurements were per formed on the oxygen molecule and water vapour. A com parison between the experimental results and the tabulated spectroscopic da ta led to an excellent correlation with measurements made on water vapour w hereas observations on the oxygen showed discrepancy. This study demonstrat es that the remote generation of a white light source represents a new way to access the range-resolved multi-trace gas analysis in the atmosphere.