  We have used an ultra-low threshold continuous-wave Optical Parametric
Oscillator (OPO) to reduce the quantum fluctuations of the reflected pump beam
below the shot noise limit. The OPO consisted of a triply resonant cavity
containing a Periodically-Poled Lithium Niobate crystal pumped by a Nd:YAG
laser and giving signal and idler wavelengths close to 2.12 microns and a
threshold as low as 300 microwatts. We detected the quantum fluctuations of the
pump beam reflected by the OPO using a slightly modified homodyne detection
technique. The measured noise reduction was 30 % (inferred noise reduction at
the output of the OPO 38 %).
