External photoacoustic detection of a trace vapor inside a multimode laser

We combine highly sensitive intracavity absorption spectroscopy in a multim ode laser with external photoacoustic detection, providing high detectivity . Photoacoustic measurements of the intracavity iodine concentration in a R hodamine 6G laser are compared with simultaneous spectral recordings. They demonstrate slightly improved overall sensitivity and a greatly enhanced dy namic range of 5 orders of magnitude that may be shifted along the absolute scale of absorber density. (C) 1999 Optical Society of America.