The external-resonator cw spin-flip Raman laser; output characteristics and spectroscopic applications

The characteristics of a stable, external-resonator spin-flip Raman laser (SFRL), pumped by a cw carbon monoxide laser of controlled mode quality and spectral content, are determined using a combination of molecular spectroscopy, Raman amplifier and confocal Fabry-Perot interferometer measurements, and heterodyne detection. Single-frequency output of a free-running external-resonator is demonstrated with an inherent linewidth of <10 kHz and a short-term frequency jitter of ?100 kHz. With the resonator length actively controlled to lock an axial mode frequency to the peak of the spontaneous gain, the linewidth of the SFRL output was maintained below 2 MHz. In this mode of operation, small variations in the output tuning rate, corresponding to the magnetic field dependence of the conduction-electron g-factor, were calibrated. Molecular absorption spectra obtained using gas cells both inside and outside the resonator have been used to illustrate the high resolution, wide-range tuning capability and sensitivity of the system. Lambda-doubling of the {Mathematical expression} of the Q-branch head of nitric oxide was measured for values of J down to 13/2, below which the splitting is less than the Doppler width. The splittings agreed with predictions using parameters obtained by conventional spectra for higher J-values. © 1979 Springer-Verlag.