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19 October 1983 Precision Measurements By Optical Heterodyne Techniques
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Detection systems with high sensitivity are of interest in all fields of science and engineering. No exception to this generality is the desire to be able to detect small absorptions or phase shifts of an optical beam, whether that be for detection of weak absorp tion of dilute atomic or molecular systems or for detecting small length changes in optical cavities for gravity wave research, etc. The past 15 years have seen the development of a number of good techniques for enhancing sensitivity in the detection of such perturbations to an optical beam. Almost invariably the high sensitivity detectors are laser-based systems, for example: direct subtraction of intensity fluctuations1 removal of intensity fluctuations by active control,2 laser intracavity absorption,3 derivative spectroscopy, polarization spectroscopy,4 intermodulation techniques,5 interferometric spectroscopy,6 polinex,7 heterodyne-detected Raman spectroscopy,8 etc. There are other techniques with high sensitivity which do not observe the optical beam directly but rather observe the effects of absorption from the optical beam, for instance fluorescence detection,9 optogalvanic spectroscopyl10 and opto-acoustic spectroscopy.11 Most of the methods, by some means, try to suppress the background noise which is not inherent on the signal.
© (1983) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
L. Hollberg, Ma Long- sheng, M. Hohenstatt, and J. L. Hall "Precision Measurements By Optical Heterodyne Techniques", Proc. SPIE 0426, Laser-Based Ultrasensitive Spectroscopy and Detection V, (19 October 1983);

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