Abstract

Ideal intracavity laser absorption spectroscopy (ICLAS) can be explained as a competition of individual modes of a highly broadband laser sharing the same homogeneous gain medium without any coupling between each other. In such a case, a narrow spectral absorption appearing in time on the envelope of the spectrum follows the classical Lambert-Beer absorption law with an equivalent absorption path L_eq=c.t_g. [1]. The limitation of the sensitivity is theoretically due to the spontaneous emission and the absorbance stops to grow for a typical time τ_sp of one second for solid state lasers, which correspond to an equivalent absorption path of 300,000 km [2]. Experimentally the saturation of the sensitivity appears for a much shorter time τ_NL which decreases when the pump power increases. This suggest that non linear coupling between modes exists and play an important role in the spectro-temporal dynamics [3,4].

© 1996 IEEE