Self-starting of an additive-pulse mode-locked color-center laser.

Self-starting of additive-pulse mode-locking (APM) behavior has been observed in a NaCl:OH color-center APM laser over the wavelength range of 1.52-1.60 microm. Pulses as short as 160 fs have been produced at a wavelength of 1.55 microm in a stable pulse train. High-power levels in the fiber are required for the mode locking to self-start. The large fiber power makes it difficult to stabilize the cavity length by conventional methods: The feedback signal must now be derived from the second harmonic of the laser output. The self-starting APM laser exhibits less noise than the synchronously pumped APM laser because of the lack of pulse walk-off effects that are characteristic of the synchronously pumped APM laser.