			10min:

CW FIBER LASER CAVITY RING DOWN SPECTROSCOPY.

WEIDONG CHEN, JULIEN COUSIN, Laboratoire de Physicochimie de l'Atmosphère, Université du Littoral Côte d'Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque, France; SAMIR KASSI, ALAIN CAMPARGUE, DANIELE ROMANINI, Laboratoire de Spectrométrie Physique, Université J. Fourier de Grenoble, 140 rue de la Physique, 38402 St Martin d'Hères, France.

Application of a tunable near-infrared Erbium doped fiber laser to continuous-wave (cw) cavity ring down spectroscopy (CRDS) is reported. The laser is widely tunable in the spectral region of 1542-1600 nm by temperature tuning with a laser linewidth of sim kHz. This ultranarrow linewidth is highly desirable for efficient cw laser coupling to a high-finesse ring down cavity. Cavity ring down spectra of N₂O and C₂H₂ have been recorded near 1.544 µm. Measurements of N₂O concentration have been performed as well with high dynamic range varying from 100 % purity to some tens ppb with a minimum measurable absorption coefficient of about 10^-10 cm^-1. Preliminary results will be presented.