High precision frequency calibration of tunable diode lasers stabilized on an internally coupled Fabry-Perot...

For very high precision molecular spectroscopy we use a tunable diode laser which is frequency locked to an internally coupled Fabry-Perot interferometer (icFPI). The spectra are calibrated by means of the interference pattern of an iodine stabilized He-Ne reference laser which is simultaneously coupled into the icFPI. In this paper the exact relation between the diode laser frequency and the He-Ne fringe number is derived and a convenient calibration procedure yielding a frequency accuracy of 5 x 10(-5) cm(-1) at 10 microm is described.