The condition of a bifurcation of a roundtrip time of ultrashort pulses (USP) in the Ndlaser with shorttime resonant modulation of loss is found out experimentally. This condition is exhibited in the period doubling in the area of a small detunings of the modulation frequency and an intermodal interval. It is revealed, that the pumping level (amplification in the active medium) is a major factor, influencing this effect.
