Squeezing in a quasi-phase-matched LiNbO_3 waveguide

We report traveling-wave quadrature squeezing at 1064 nm in a quasi-phase-matched LiNbO(3) waveguide, avoiding the gain-induced diffraction encountered in bulk squeezing experiments. The 10-mm-long singlemode waveguide parametric amplifier exhibited a gain of 1.9, averaged over the 20-ps mode-locked pulses, with only 0.5 W of peak pump power at 532 nm. Independent waveguides were employed for the degenerate parametric amplifier squeezer and for the second-harmonic generator that produced the pump for the parametric amplifier. We measured phase-sensitive amplification versus pump power and found close agreement with theory. The observed 14% squeezing correlates closely with the predicted value, based on the measured phase-sensitive amplification and 40% overall detection efficiency. Impedance-matched electrically resonant detection was used to boost our squeezing measurement signals substantially above the background level.