Rise Time of Pulsed Parametric Oscillators

Gain saturation of an Nd-glass amplifier by 1.06-pmlight pulsesis determined by the lifetimes and degeneraciesof thetwo laser states aswell a s by thermalization rates among the com-ponents of the twomultiplets to which thelaserlevels belong.Reportedaremeasurements showing thatalthoughsmall signalgain was the same foramplified microsecond and picosecond pulses,comparable energy gain saturation occurred when the energy densityof the mode-locked pulses was 1.9 times smaller than the amountfor the microsecond pulsesindicatingterminallevel filling withthe shorter pulses. Our measurements indicate the terminal laserlevel, whichis one of two unresolved groups in the 4 1 1 1 , 2 multiplet,has a lifetime greater than50 ns and a degeneracy likely to be one ortwo. Pulsetrain distortion duetosaturating amplification wasmeasured to k d whether the thermalization rates among the levelsof the laser multiplets were fast or slow compared to the 10-1*-spulses, butexperimentaluncertainties prohibit a determination.