Pulsed squeezed-light measurement: A new technique

A transient noise measurement scheme is described to observe pulsed squeezing generated by means of parametric downconversion of a Q-switched laser. In the usual implementation of balanced-homodyne detection, the vacuum-state noise level is determined by the average local oscillator power. However, if the local oscillator is derived from a pulsed laser, as is the case in our experiments, the associated peak power can easily saturate the detectors along with the subsequent electronics. To overcome this limitation we have implemented a hybrid frequency-time-domain measurement scheme in which the vacuum-state noise level is determined by the peak, instead of the average, local oscillator power, thus avoiding the saturation problem.