Holographic Spectroscopy Diffraction from Laser-Induced Gratings

The introduction of lasers into spectroscopic instrumentation has produced outstanding gains in detection compared with conventional light sources. These improvements arise not only from the higher optical power output of the laser but also from the unique coherence properties of laser radiation, A new class of sensitive spectroscopic techniques has been developed in which heat produced by nonradiative decay of excited species perturbs the optical path within the sample. Differences in the optical propert ies of photoproducts can also perturb the optical path. The spatial coherence of a laser beam probing the sample makes it possible to observe extremely small perturbations in optical path, and thus very weakly absorbing samples can be detected.