AMPLITUDE SQUEEZING BY MEANS OF QUASI-PHASE-MATCHED 2ND-HARMONIC GENERATION IN A LITHIUM-NIOBATE WAVE-GUIDE

We demonstrate that traveling-wave second-harmonic generation produces amplitude-squeezed light at both the fundamental and the harmonic fre quencies. Quasi-phase-matched second-harmonic conversion efficiencies approaching 60% were obtained in a 26-mm-long single-mode LiNbO3 waveg uide with pulses from a mode-locked laser at 1.53 mu m. The amplitude noise of the transmitted fundamental field was measured to be 0.8 dB b elow the shot-noise level, and the generated 0.765-mu m harmonic light was measured to be amplitude squeezed by 0.35 dB. The conversion-effi ciency dependence of the observed squeezing at both wavelengths agrees with theoretical predictions. Waveguide losses appear to degrade the squeezing, but the maximum observed squeezing is currently limited onl y by the available input power. (C) 1997 Optical Society of America.