Abstract

Squeezed light with partial coherence is generated via optical parametric amplification (OPA) in a KTiOPO₄ crystal that is pumped by the second harmonic of a Q-switched multimode Nd:YAG laser.¹ More than 1 dB of squeezing is observed when a proper mode of the downconverted light is homodyned with the 380-ns multilongitudinal-mode local oscillator (LO) pulse. In such a system, large OPA gain is easily obtained in a single-crystal signal-pass setup. The detection of squeezed light is, however, not straightforward. In the usual implementation of a balanced homodyne detection scheme,² the vacuum-noise level, as measured on a radio frequency spectrum analyzer, is determined by the average LO power. If the LO is derived from a Q-switched laser, as is the case in our experiment, the associated peak power can easily saturate the detectors and the subsequent electronics. To overcome this limitation, we have implemented a hybrid frequency/time domain measurement scheme in which the vacuum noise level is determined by the peak (instead of the average) LO power. The LO average power requirement is thus relaxed and the detector saturation problem avoided.

© 1989 Optical Society of America