Time-resolved nonlinear absorption modulation in GaAs/AlGaAs multiple-quantum-well waveguides at 1.06 mu m

Time-resolved nonlinear absorption modulation due to two-photon absorption (TPA) and free carrier absorption (FCA) was demonstrated in GaAs/AlGaAs waveguides at 1.06 mu m. For a peak input intensity of 4.5*10/sup 11/ Wm/sup -2/, there was a maximum absorption modulation of 35%. This was caused by TPA, so that the recovery time was limited by the laser pulsewidth alone. At a peak input intensity of 1.5*10/sup 12/ Wm/sup -2/, a 65% absorption modulation was observed. This consisted of two components: an instantaneous effect due to TPA and also a slower component, attributed to FCA, whose recovery time was limited by the carrier lifetime. A theoretical model was also derived which provided a good fit to the experimental data.<
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