Abstract

Recently, we have observed as much as 7 dB of quantum-noise reduction in the direct difference detection of twin-beam signal and idler outputs from a traveling-wave optical parametric amplifier (OPA).¹ The OPA, which consists of a type-II phase-matched KTiOPO₄ crystal, is pumped by the second harmonic of a mode-locked and Q-switched Nd:YAG laser. Here we describe an experiment in which we used these twin-beam pulses to improve on the optimal (shot-noise-limited) direct-detection signal-to-noise ratio (SNR) that can be achieved with coherent-state pulses of light of the same peak power.

© 1990 Optical Society of America