Abstract

Frequency modulation (FM) spectroscopy was first demonstrated by Bjorklund¹ in the visible region using a ring dye laser. The basic scheme of FM spectroscopy calls for phase modulation of the laser beam either by an external electrooptic modulator or in the case of diode lasers by modulating directly the injection current. The requirement of modulating the laser at high frequencies (several gigahertz), so that the spectral feature of interest can be probed by a single Fourier component of the laser power spectrum, introduces the need for high-speed detectors which are not always available commercially and have small and damage-sensitive surfaces.

© 1987 Optical Society of America