Long-term frequency-stabilized Ar-ion laser system for high-resolution Raman spectroscopy of gases.

An Ar-ion laser with a measured single-mode linewidth of 5 MHz at 488 nm has been stabilized to approximately 1 MHz. The stabilization has been obtained by means of a Fabry-Perot interferometer as wavelength reference and a solid étalon as mode selector. The error signal is generated by modulation of the length of the laser cavity. The stabilization system is able to keep the wavelength fixed for periods of more than 100 h.