Demonstration of high sensitivity spectroscopy with squeezed semiconductor lasers

We have employed amplitude squeezed semiconductor lasers in a frequency-modulation spectrometer for the detection of absorption signals of atomic cesium, The sub-quantum limit radiation allows to evidence signals that are below the shot noise limit of the laser source, We have used a set-up with extremely low effective absorptions in order to quantitatively assess the potential sensitivity enhancement in comparison with previous high sensitivity spectroscopy experiments. A narrow detection bandwidth and a high modulation index, together with the sub-shot noise source lead to a minimum detectable signal that is a few parts in 10(8). (C) 1997 Elsevier Science B.V.