Quantum-noise measurements in high-efficiency single-pass second-harmonic generation with femtosecond pulses

The quantum-noise properties of single-pass second-harmonic blue-light gene ration with femtosecond pulses have been measured. A conversion efficiency of as much as 63.5% of second-harmonic generation at 428.8 nm was observed in a KNbO3 crystal with femtosecond (130-fs) pulses with wavelengths center ed at 857.6 nm. The quantum noise on the generated blue light was measured to be 1.0 dB (1.4 dB of squeezing inferred) below the shot-noise limit. The noise reduction was found to be sensitive to the average power and the cen ter wavelength of the input fundamental pulses under the condition of stron g pump depletion. (C) 1999 Optical Society of America OCIS codes: 270.0270, 190.2620.