TUNABLE DIODE-LASER SPECTROMETER WITH CONTROLLED PHASE FREQUENCY EMISSION

A spectrometer using a monomode tunable diode laser as a source is des cribed. The phase of the emission is controlled by the interference pa ttern given by a Michelson interferometer. The phase noise is thus dra stically reduced and the wavenumber measurement precision is better th an 10(-8). Also, the intensity absorbed by a gas is known to a precisi on better than 10(-3). To illustrate the possibilities of the spectrom eter, brief examples of inelastic molecular collision effects in gases (pressure broadening, mixing, and shift for V-R lines) will be given. The low noise level and precise wavenumber measurements allowed Pliva to build an effective absorption spectrum with linewidths significant ly narrower than Doppler-limited ones using deconvolution methods. (C) 1994 Academic Press, Inc.