Frequency stabilization of an AlGaAs laser using the thorium optogalvanic spectrum

The possibility of using the thorium optogalvanic spectrum as a wavelength reference spectrum is shown. The frequency stabilization of an AlGaAs laser using an optogalvanic signal from the spectrum of metallic thorium vapor is reported. A hollow-cathode electric discharge tube, designed and built in a laboratory, has been used to obtain the resonant optogalvanic line corresponding to the ThI 10414.1364 cm/sup -1/ (fds/sup 2/)-23201.9890 cm/sup -1/ (fdsp) transition (781.77699 nm). In preliminary results, the closed-loop frequency fluctuations were reduced within 150 kHz peak-to-peak for a time constant of 1 s. This value corresponds to the discharge white noise, estimated to be 0.1 mu V, which constitutes the intrinsic limit.<>