We show both theoretically and experimentally that interference fringe signals can always be suppressed to improve the signal-to-noise ratio, provided that the modulation frequency is of the order of the absorption linewidth or higher. Suppression of optical interference fringes by more than 1 order of magnitude and signal-to- noise ratio enhancement of more than 13 dB is demonstrated by use of a proper choice of laser modulation frequency. A further fringe reduction of 10 dB is possible by adjustment of the local oscillator phase.
© 1995 Optical Society of America
Original Manuscript: March 17, 1995
Published: August 15, 1995
Dag Roar Hjelme, Steinar Neegård, and Erling Vartdal, "Optical interference fringe reduction in frequency-modulation spectroscopy experiments," Opt. Lett. 20, 1731-1733 (1995)