An improvement in precision beyond the limit set by the vacuum-state or zero-point fluctuations of the electromagnetic field is reported for the detection of amplitude modulation encoded on a weak signal beam. The improvement is achieved by employing the squeezed light from an optical parametric oscillator to reduce the level of fluctuations below the shot-noise limit. An increase in signal-to-noise ratio of 2.5 dB relative to the shot-noise limit is demonstrated.
© 1988 Optical Society of America
Min Xiao, Ling-An Wu, and H. J. Kimble, "Detection of amplitude modulation with squeezed light for sensitivity beyond the shot-noise limit," Opt. Lett. 13, 476-478 (1988)