TIMING JITTER AND PUMP-INDUCED AMPLITUDE-MODULATION IN THE COLLIDING-PULSE MODE-LOCKED (CPM) LASER

We characterize the timing jitter and spurious amplitude modulation of colliding-pulse mode-locked (CPM) lasers. The absolute jitter (the jitter of the laser alone) varied between 5 and 10 ps rms in a 50 to 500 Hz bandwidth. The smallest measured relative jitter (timing fluctuations between the CPM and a radio-frequency (RF) synthesizer synchronized to the CPM) was 1.8 ps rms in a 2 Hz to 1 kHz bandwidth. Separate from the jitter, spurious modulation in the CW pump laser mixes with the CPM pulse train to produce a set of discrete amplitude-modulated sidebands in the power spectrum of the CPM output. The frequencies of these sidebands change with cavity length, and the sidebands can be eliminated by operating the pump laser in a single longitudinal mode.