Measurement of time dependent optical gain using frequency modulation spectroscopy

Frequency modulation (FM) spectroscopy is demonstrated to be an attractive tool for gain analysis. It offers the three major features: a) potential high sensitivity in absolute gain measurement, b) high spectral resolution allowing the determination of the spectral gain profile, c) high temporal resolution capable of monitoring gain in short-pulsed systems. As an example, results of a gain analysis of the 6328 å line in a He-Ne discharge are presented.