Walk-off effect on the generation of ultrashort pulses from cw light using cross-phase modulation in optical fibers

Abstract

We investigate the role of walk-off in the evolution of a weak cw wave in the anomalous-dispersion regime modulated by an intense picosecond pulse through cross-phase modulation. The cw wave can evolve into a short pulse whose duration and amplitude will depend on the degree of walk-off. When the walk-off length is shorter than necessary for short-pulse formation, the signal wave becomes amplitude modulated with a modulation depth of a few percent. In this case a frequency chirp exists in the signal wave, which can be used to generate short pulses on propagation through an appropriate dispersive element.

Synchronously pumped 3.5μm mode-locked fiber laser

“…Synchronously pumped mode-locking technique is classified as a kind of active phase modulation mode-locking based on the cross-phase modulation effect [10][11][12][13][14] . Is requires a pulsed pump whose repetition rate matches to the fundamental frequency of the laser cavity, f0 = c/(2*L') for a linear cavity, while c is the velocity of light, L' is the optical path.…”