Multiwavelength scintillation effects in a long-path CO2 laser absorption spectrometer

The noise properties of a rapidly switched two-wavelength CO2 laser spectrometer are investigated in the framework of weak scattering turbulence theory; experiments involving laser beam propagation over a 600-m path to a small-aperture transmitter are also conducted. Particular attention is given to the effectiveness of the multiwavelength correlation technique for controlling scintillation noise in the long-path absorption spectrometer. Noise reduction through use of multiwavelength coherence is found to be dependent on similarity of the beam parameters and a small relative wavelength difference.