FREQUENCY-STABLE AND ULTRANARROW-LINEWIDTH SEMICONDUCTOR-LASER LOCKEDDIRECTLY TO AN ATOMIC-CESIUM TRANSITION

We describe a new method for semiconductor laser FM noise reduction. A Doppler-free Faraday resonance in Cs vapor provided optical feedback, and FM sideband saturation spectroscopy in a second Cs cell provided electronic feedback. The combined optical and electronic feedback allo wed us to reduce the low-frequency FM noise power by more than 6 order s of magnitude, which resulted in a sub-100-Hz-linewidth semiconductor laser locked directly to an atomic transition frequency. (C) 1998 Opt ical Society of America.