Sub-shot-noise frequency-modulation spectroscopy by use of amplitude-squeezed light from semiconductor losers

We have demonstrated sub-shot-noise FM spectroscopy on thermal cesium atoms , using amplitude-squeezed light from a semiconductor laser. The light sour ce used in our experiment was a custom-made GaAs transverse junction stripe semiconductor laser featuring broadband amplitude squeezing and a large FM bandwidth. We have also developed a new technique by which a semiconductor laser can be frequency modulated with infinitesimally small residual AM an d with complete preservation of the squeezed-amplitude fluctuations. (C) 20 00 Optical Society of America [S0740-3224(00)00802-X].