Pulsewidth-variable relaxation-free optical millimeter-wave generation from a semiconductor fiber ring laser

Optical pulses of 10-50-GHz repetition frequencies have been generated by rational harmonically mode locking a semiconductor fiber ring laser using cross-gain modulation by 10-GHz external double optical pulses. The output is pulsewidth-variable from 6.4 to 14 ps, wavelength-tunable from 1530 to 1560 nm, and remains relaxation-free even though the injected external optical pulses have large relaxation oscillation noise.