Passive mode-locking of the Nd-glass oscillator at high repetition rate with thermally compensated phosphate glasses

The performance of the passively mode-locked Nd-glass laser has been investigated at repetition rates of up to 5 Hz for seven different varieties of Nd-doped silicate, fluoro-phosphate, and phosphate glass rods. Those phosphate rods which are thermally compensated (LHG-8, EV-4, Q-100) were found to permit mode-locking at 5 Hz with no apparent thermal distortion. The other rods had self-imposed repetition rate limits of less than 0.5 Hz. All rods were evaluated under conditions of TEM₀₀ field distribution. High resolution streak camera and time resolved spectrogram measurements showed that 4 ps time-bandwidth limited pulses were produced with thermally compensated phosphate glass only in the leading edge of the pulse train and that self-phasemodulation was present in the later pulses for all of the glasses.