Dynamic properties of second-harmonic intensity of a nanosecond-order laser pulse

Numerical and experimental results on the dynamic properties of the second-harmonic generation of Q-switched nanosecond-order laser pulses are described by reexamining the influence of the imperfect phase-matching condition. For a type-I noncritical phase-matching scheme, the fluctuation in the second-harmonic intensity owing to the change in environmental temperature can be effectively avoided by using the conversion region in the second-harmonic generation. In addition, the instability of the second-harmonic intensity owing to the variation in the fundamental intensity might be suppressed by introducing an optimized phase-mismatching condition to the reconversion region if the fundamental laser pulse has a flat-top profile. These approaches are expected to be applied for the peak-intensity stabilization of the pump laser used in optical parametric chirped pulse amplification.