A fast pulsed jet of is applied for the loss modulation of a CW laser and pulse trains of repetitively Q-switched generation are recorded in the frequency range 0.1-1 kHz. The laser-pulse shape and its duration depend on the jet-driving frequency, the position of the pulsed stream relative to the intracavity beam and the temporal changes of the absorber density. A controllable, full-depth modulation of the laser output at frequencies in the range between the jet frequency and harmonics is obtained. The process is ascribed to the interaction of a vortex trail evolving in the jet-edge region. The resulting modulation of the laser gain is ascribed to the common effect of the absorber bleaching and beam refraction.