Picosecond pulse generation by self-phase modulation in an actively mode-locked and Q-switched phosphate glass laser

The generation of 4 ps pulses by an actively mode-locked and Q-switched phosphate glass laser is reported. The pulse width is found to decrease rapidly after the peak of the Q-switched pulse train, accompanied by distortion of the pulse temporal profile from the initial Gaussian shape. Theoretical analysis demonstrates that pulse shortening takes place when the phase-modulated pulse passes through the etalon in the laser cavity. Modulation in the phase of the pulse is caused by the nonlinear refractive indices of the laser rod and the two acousto-optic elements used for mode-locking and Q-switching. (author)