Infrared tunable diode laser control: frequency stabilization and digitization of spectra leading to high sensitivity and accurate frequency scale

An infrared diode laser is frequency stabilized to a tunable internally coupled Fabry-Perot interferometer (icFPI). Diode laser spectra are digitally recorded utilizing a step-by-step tuning and stabilization sequence of the icFPI. Fringes from a frequency stabilized reference He-Ne laser are used to control digital sampling steps. While improving significantlythe spectral SNR, this method is combined with a confocal Fabry-Perot etalon, thus providing a frequency scale accuracy of ~3.5 x 10(-5) cm(-1) over a 1-cm(-1) scan. The method is shown to be consistent with high resolution Fourier transform and heterodyne spectroscopy results.