Optical fringe reduction technique for FM laser spectroscopy.

A simple and effective fringe reduction technique for FM 200 250 laser spectroscopy is discussed. A factor of 20 fringe reduction was observed in two-tone FM spectroscopy of water vapor. Theoretical simulations are compared to the exere perimental results.

Single-tone and two-tone AM-FM spectral calculations for tunable diode laser absorption spectroscopy.

A generalized theory for optical heterodyne spectroscopy with phase modulated laser radiation is used which allows the calculation of signal line shapes for frequency modulation spectroscopy of Lorentzian gas absorption lines. In particular, synthetic spectral line shapes for both single-tone and two-tone modulation of leadsalt diode lasers are presented in which the contributions from both amplitude and frequency modulations are included.