A new type of wavelength-modulation laser spectroscopy is accomplished by utilizing an external phase modulator driven at radio frequencies large compared to the width of the spectral feature of interest. The spectral feature is probed by a single frequency-modulated (FM) sideband, and the associated absorption and dispersion are measured by monitoring the resulting radio-frequency beat signal. Experimental results are presented for the measurement of Fabry–Perot resonances, I2 vapor absorption lines, and saturation holes in Na vapor.
© 1980 Optical Society of America
Original Manuscript: September 17, 1979
Published: January 1, 1980
Gary C. Bjorklund, "Frequency-modulation spectroscopy: a new method for measuring weak absorptions and dispersions," Opt. Lett. 5, 15-17 (1980)