Properties of the pulse train generated by repetition-rate-doubling rational-harmonic actively mode-locked Er-doped fiber lasers

We demonstrate for the first time to our knowledge, experimentally and theo retically, that the pulse-to-pulse amplitude fluctuations that occur in pul se trains generated by actively mode-locked Er-doped fiber lasers in a repe tition-rate-doubling rational-harmonic mode-locking regime are completely e liminated when the modulation frequency is properly tuned. Irregularity of the pulse position in the train was found to be the only drawback of this r egime. One could reduce the irregularity to a value acceptable for applicat ions by increasing the bandwidth of the optical filter installed in the las er cavity. (C) 2000 Optical Society of America.