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We report the generation of sub-Poissonian pulses of light by means of traveling-wave second-harmonic generation (SHG) in a type II phase-matched nonlinear crystal. On direct detection, the quantum noise on the output light, which is polarized orthogonally to the input fundamental field, is measured to be below the shotnoise limit by as much as 0.3 +/- 0.2 dB (6 +/- 4%). We show that the input fundamental-power dependence of the measured Fano factor, direct-detection noise as a fraction of the shot-noise limit, is in qualitative agreement with the quantum theory of SHG.

We have analyzed squeezing of the fundamental field by means of traveling-wave, type-II phase-matched, secondharmonic generation, taking into account depletion of the fundamental field and phase mismatch between the fundamental and the harmonic fields. For the phase-matched case we show that the generated squeezing is S = 1 - gamma, where gamma is the harmonic conversion efficiency. In the case of a large phase-mismatch we have identified a new mechanism that generates squeezing. It is the nonlinear phase shift of the fundamental field that is due to the cascaded chi((2)) nonlinearity.

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