Study of exciton dynamics in InGaAs/InP quantum wells using a femtosecond optical parametric amplifier

Abstract
We investigated the excitondynamics in InGaAs/InP quantum wells using a novel infrared tunable femtosecond lasersource, based on an optical parametric frequency converter pumped by a femtosecond Ti:sapphire laser. The wide tuning range of this source allowed to excite three different excitonic resonances in the absorptionspectrum of the sample. The n=1 heavy‐hole excitons are approximately eight times more efficient than free electron‐hole plasma in the absorptionsaturation. This value is much higher than that measured in GaAs quantum wells. The exciton ionization time constant of the n=1 and n=2 heavy‐hole excitons has been measured to be 170 and 100 fs, respectively. No evidence of the n=1 light‐hole excitondynamics was found in the measurements. The study of the dynamics at the n=2 heavy‐hole resonance allowed the measurement of a n=2 to n=1 intersubband relaxation time of 1 ps.

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