CHARACTERISTICS OF A VISIBLE MODULATION INSTABILITY FIBER LASER

Cross-phase modulation has been harnessed to construct a modulation in stability laser operating at 514.5 nm. The laser output consists of or thogonally polarized upshifted and downshifted sideband pulses separat ed in wavelength by 2.1 nm from the pump. The laser configuration has been found to generate a much more stable source of terahertz modulate d light pulses than the single-pass configuration previously used to d emonstrate modulation instability in the visible. The extra stability arises from the feedback, which provides a seed for the modulation, an d hence a reduction in the pump power necessary compared with the sing le-pass configuration, which in turn reduces the Raman gain, and the a symmetry of the sideband amplitudes. The sideband pulses can be combin ed to generate a modulated envelope of 4-THz oscillations with a durat ion of 10-15 ps.