We implement high sensitivity spectroscopic experiments involving infrared vertical external cavity surface emitting multiple-quantum-well lasers ( external cavity VCSEL : VECSEL ). around 1 µm.

  These experiments are based on intracavity laser absorption ( ICLAS ) analyzed by time-resolved Fourier transform spectroscopy ( TRFTS ).

    Broadband absorption spectra with equivalent path length of the order of 150 kilometers are recorded. Typically, the minimum absorption coefficient is of the order of 1 x 10^-10 cm^-1Hz^-1/2 for simultaneously acquired 10⁴ spectral elements.