SOLID-STATE LASER SPECTROSCOPY USING A REFERENCE ABSORBER
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Date
1975
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Publisher
Ohio State University
Abstract
The output from a homogeneously-broadened, long-pulse, solid-state laser consists of a series of spikes and spectrally may be several nanometers wide. Each spike has a very narrow wavelength range that varies from spike to spike. This fact can be used to obtain high resolution spectral profiles of coincident gas absorption lines by using a Fabry-Perot etalon to identify the wavelength of the individual spikes. The method consists of (1) the reference amplitude path, (2) the absorption path, and (3) the known wavelength-dependent reference absorption path (a Fabry-Perot etalon). The ratio of the absorption to the reference amplitude path signals allows the transmittance through the gas to be calculated. The etalon to reference amplitude ratio is used to identify laser spike wavelengths with respect to each other. The laser spectral output (or parts of it selected by a spectrometer) is situated on one side of a low finesse etalon bandpass (40\% reflection optics are used). Different wavelength spikes experience different attenuations in passing through the etalon. The varying attenuation makes it possible to distinguish between spikes of different wavelengths, A minicomputer controlled pulse-height analyzer Is used to store, analyze, and display the Information from the three simultaneous signals. This technique was utilized to resolve the 1645.1 nm R(6) transition of the $2\nu_{3}$harmonic In $^{12}CH_{4}$ using coincident erbium YAC laser emission. Results are presented.
Description
Author Institution: Electrical Engineering Department, New Mexico State University; Atmospheric Sciences Laboratory, United States Army Electronics Command