Squeezing in traveling-wave second-harmonic generation

We have analyzed squeezing of the fundamental field by means of traveling-wave, type-II phase-matched, second-harmonic 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 − γ, where γ 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 χ⁽²⁾ nonlinearity.