TUNABLE IR LASER WAVELENGTH CALIBRATION USING A MODIFIED LABORATORY FTS INTERFEROMETER

Abstract

Knowledge of the laser wavelength is essential in tunable IR laser spectroscopy. The scanning Michelson interferometer has the potential to compare the IR laser wavelength to a single, well-known calibration wavelength (e.g., HeNe laser) over a wide IR spectral range. In contrast to other recent work with scanning Michelson interferometers, we have added a phase-lock multiplier and counters to a $0.1 Cm^{-1}$ FTS laboratory interferometer to achieve an accuracy of $10^{-3}cm^{-1}$. This Idealab interferometer incorporated cats-eye mirrors, but its other features are probably representative of typical commercial interferometers. Measurements of a stable $CO_{2}$ laser have indicated a precision and calibratable accuracy of $0.001 cm^{-1}$ with $CO_{2}$ use of the HeNe laser monitor supplied with the interferometer. Achievement of the $0.0001 cm^{-1}$ precision and accuracy expected with the phase-lock multiplier is still under study as is the application of the wavemeter to the calibration of tunable diode lasers.