Zeeman effect-based control-signal improvement for frequency stabilization of a semiconductor laser

We have stabilized the oscillation frequency of a 780-nm-band semiconductor laser using the D-2 absorption line of Rb atoms. The absorption line has a spectral width due to the natural width and Doppler width, which limits the stability of laser performance. In order to minimize the spectral spread of the absorption line, a Doppler effect-free absorption line whose spectral spread is close to the natural width was obtained by saturated absorption spectroscopy and was used for stabilization of the laser oscillation frequency However, the spectral width of the absorption line could not be further narrowed by optical means alone. In this study, the spectral width of the reference signal was further narrowed using the Zeeman effect of the Rb atomic absorption line and the newly developed PEAK and BOTTOM methods. Using this reference signal, the width of the frequency discrimination curve was narrowed. As a result, the laser oscillation frequency more accurately tracks the reference frequency. In addition it was confirmed that the frequency discrimination curve could be swept. (C) 1998 Scripta Technica.