Abstract: A novel practicable type of gaseous optical gain medium for efficiently generating intense, highly monochromatic, continuous-wave (CW) or pulsed, coherent light beams is disclosed. Gain results from nonlinear optical pumping of a gas of ?-type “three-level” atoms, coherently phased (“dressed”) via application to the medium of two monochromatic laser beams tuned to the resonance frequencies ?0 and ??0. Nonlinear optical pumping of the “dressed-atom” gas is accomplished through the combined action of two separate physical processes: (1) A low pressure gaseous discharge, occurring continuously within the vessel containing the gain medium, produces intense narrow-band fluorescence at ?0 and ??0 through the process of electron impact excitation (EE).

Abstract: A coherent tunable narrow band IR source in the vicinity of 16 .mu.m is achieved by four-wave parametric mixing in parahydrogen. A pair of colinear laser beams, one from a narrow band CO.sub.2 laser, and a second from a multiline laser with output of wave number significantly below 14,400 cm..sup.-1, is focused in a parahydrogen containing cell. The multi-line laser beam drives a Raman process in the cell. The narrow band CO.sub.2 input beam mixes with this driver beam and the Stokes wave resulting from the Raman process to produce a 16 .mu.m output beam. Tuning of the CO.sub.2 laser allows tuning of the 16 .mu.m radiation emitted by the parahydrogen cell.

Abstract: Apparatus for producing tunable intense coherent radiation at approximately 628 cm..sup.-1 with a line width less than 0.1 cm..sup.-1. The apparatus includes an optical cavity containing a vapor cell and pumping means including at least one optical pumping source for directing energy at the cavity. In one embodiment the cavity encloses a material capable of stimulated emission in response to said pumping. The material has at least three atomic energy levels with at least a first and second atomic energy level separated by a particular energy quantum approximately equal to 628 cm.sup.-1 ; a transition from said first to said second atomic energy level favored over all other possible transitions from said first atomic energy level; said third atomic energy level, from which atoms can be pumped to said first atomic energy level in response to said pumping means. While this is consistent with classical laser operation the apparatus disclosed herein can also be used for stimulated Raman scattering.

Abstract: An intense broadband continuum light pulse of uniform spectral intensity and short time duration is generated. This continuum pulse is then downconverted in frequency to a region of interest, preferably in the infrared region, by applying it as a pump pulse to a molecular or atomic vapor so as to induce stimulated Raman scattering. The resulting Raman Stokes pulse surprisingly tends to have the same spectral bandwidth, intensity uniformity and time duration as the pump continuum pulse.The downconverted continuum pulse (the Raman Stokes pulse) is then used to probe a sample. The sample converts the uniform spectral intensity distribution of the probe pulse into a nonuniform spectral intensity distribution which contains the absorption spectrum of the sample. This spectrum pulse has the same spectral bandwidth and time duration as the Raman Stokes pulse and is finally upconverted in frequency to a region where the spectrum pulse can be conveniently recorded.