Ultrafast spectroscopy of aerosol particles and microcavities
We have developed a real-time optical technique that discriminates bioaerosols among urban background aerosols, especially soot emitted by diesel engines. This technique is based on the multipulse ultrashort excitation of instrinsic fluorophors of bioaerosols and identifies their molecular dynamics. Specific fingerprints of bacteria and hydrocarbons could be exhibited. This study is a first step towards the all-optical identification of biological material. Pump-probe spectroscopy has also been employed to probe the propagation dynamics of a femtosecond pulse in a 2D spiral-shaped microcavity. An imaging technique using pulse correlation has been developed to visualize with femtosecond time resolution the propagation of a wavepacket in the microcavity. FDTD simulations have enabled to interpret our observations and to exhibit an original output coupling process, that implies the reflexion of the evanecent wave on the discontinuity of the spiral.