Near-resonant holographic interferometry

Abstract

A technique is discussed that measures the quantitative concentration of various species in a flow-field using near-resonant holography. This technique utilizes two laser wavelengths to probe the species specific anamolous dispersion on either side of an absorption line. By exposing two holograms simultaneously with these two wavelengths, the recorded OPD is proportional to the species concentration. Since the holograms are recorded with only slightly different wavelengths, optical system aberrations and gas compressibility effects are removed from the reconstructed hologram fringe pattern.