The optical gain-depletion-induced mode-locking dynamics of a semiconductor optical-amplifier–based fiber ring laser (SOAFL) backward injected by a purely sinusoidally modulated or digitally encoded distributed-feedback laser diode are theoretically and experimentally demonstrated. The effect of gain depletion and waveform on the mode-locked pulse width, pulse shape, and power of the SOAFL are interpreted from theoretical simulations. The shortest pulse width of 12 ps can be generated from an optically sinusoidal-wave-modulated SOAFL. By backward injecting the SOAFL with a digitally encoded optical signal of adjustable duty cycle, one can observe the optimized gain depletion time of 400–600 ps required for mode locking the SOAFL.
© 2004 Optical Society of America
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