9500584 Morse An absorbing material placed within a laser cavity has a great effect on the output of the laser. This technique is well known using an absorption cell within the cavity of a dye laser. We propose to use the concept of intra-cavity laser absorption in conjunction with the Tm-Ho fiber laser that has gain from 1.65 to 2.095 um. Many gases have rotational-vibrational overtones in this wavelength region, and it should be possible to detect them using this sensitive technique. We believe that a field-hardened instrument that will yield spectroscopic information can be the result of such research. ***
