REPRESSION AND SPEED IMPROVEMENT OF PHOTOGENERATED CARRIER INDUCED REFRACTIVE NONLINEARITY IN INGAAS/INGAASP QUANTUM-WELL WAVE-GUIDE

For the first time, the all-optical refractive nonlinearity due to photogenerated carriers in an InGaAs/InGaAsP quantum well waveguide under various bias conditions is measured. With no bias, the nonlinearity has a slow recovery time, of the order of the recombination time of the carriers. For a coupled power of 4.3 W and a 600-mu-m long device, we measure a phase modulation of 7.5 +/- 2 radians. Under forward bias the nonlinearity is effectively quenched. Under reverse bias the nonlinearity remains, although slightly reduced. In the latter case the recovery time is dramatically reduced to approximately 50 ps.