HIGH PRECISION INTENSITY AND BROADENING PARAMETER MEASUREMENTS BY A STEP BY STEP F. T. CONTROLLED DIODE LASER

Author Institution: Laboratoire de Spectronomie Mol\'{e}culaire, Universit\'e Pierre et Marie Curie - Tour; Laboratoire de Spectronomie Mol\'{e}culaire, Universit\'e Pierre et Marie Curie - Tour; Laboratoire de Spectronomie Mol\'{e}culaire, Universit\'e Pierre et Marie Curie - Tour; Laboratoire de Spectronomie Mol\'{e}culaire, Laser AnalyticsHigh signal to noise ratios in the monochronatic emission for a diode laser generally permit rather precise measurements of line intensities. Line width determinations and broadening parameter measurements with diodes require very precise knowledge of the laser frequency. Significant improvements in measurement of width and broadening parameters can be realized by frequency locking the diode laser emission frequency to several points within the profile of the spectral line being measured. In this work a portion of the diode laser beam is sent through the Paris Longpath Fourier transform interferometer where the diode emission is locked to the Fourier transform lamb dip stabilized fringe system by controlling the polarization current through the diode. As the interferometer steps through optical path differences the diode laser emission frequency is tuned also. Elementary step sizes in these experiments correspond to a path difference $8/8 = 632.8/8$ or 79.1 nm which allows for several tens of sample points over a line profile. Each sample point has a frequency precision better than $10^{-5}$ in wavenumber units. With such precision the ``Doppler - Fizeau Width” of a line is known with a precision better than $10^{-2}$. Results in $N_{2} O \nu_{3}$ and $\nu_{2} + \nu_{3} -\nu_{3}$ bands will be given as an illustration of the method described here