EXPERIMENTAL-STUDY ON METHODS MINIMIZING THE INFLUENCE OF VELOCITY-CHANGING COLLISIONS IN DOPPLER-FREE SATURATION SPECTROSCOPY

A method based on homodyne mixing is described which facilitates the u se of rf-modulation of the pump beam for laser saturation spectroscopy together with conventional kHz lock-in amplifiers yielding a substant ial reduction of disturbing pedestals present due to collisions in an atomic vapour. The technique benefits also from the significant improv ement in the signal to noise ratio when transferring the Doppler-free signal to a frequency domain of several MHz where the interfering lase r noise is low. These experimental procedures allow measurements of hi gh quality saturated absorption spectra in vapour cells of otherwise u nfavourable high gas pressure such as in commercial see-through hollow -cathodes. In addition we report the detection of an optogalvanic sign al at rf-modulation (3.3 MHz).