OBSERVATION OF SUB-POISSONIAN LIGHT IN TRAVELING-WAVE 2ND-HARMONIC GENERATION

We report the generation of sub-Poissonian pulses of light by means of traveling-wave second-harmonic generation (SHG) in a type II phase-ma tched nonlinear crystal. On direct detection, the quantum noise on the output light, which is polarized orthogonally to the input fundamenta l field, is measured to be below the shot-noise limit by as much as 0. 3 +/- 0.2 dB (6 +/- 4%). We show that the input fundamental-power depe ndence of the measured Fano factor, direct-detection noise as a fracti on of the shot-noise limit, is in qualitative agreement with the quant um theory of SHG. (C) 1996 Optical Society of America