Conference Paper

Ultrafast processes in InAs/GaAs quantum dot based electro-absorbers

Tyndall Nat. Inst., Cork, Ireland
DOI: 10.1109/ICTON.2009.5185002 Conference: Transparent Optical Networks, 2009. ICTON '09. 11th International Conference on
Source: IEEE Xplore

ABSTRACT In this study we perform a detailed investigation of the ultrafast processes which govern the intradot recovery dynamics of a QD InAs/GaAs structure under reverse bias condition by means of the single and two colour pump-probe technique. By studying the GS and ES recoveries as a function of reverse bias voltage and fitting the experimental results with a simple rate equation model for the intradot carrier dynamics we have illustrated the dominance of Auger mediated recovery when the ES is initially populated while phonon mediated recovery dominates for the GS case. This provides opportunities for the design of the next generation of electro-absorbing devices based on QD materials.

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    ABSTRACT: Semiconductor saturable absorber mirrors (SESAMs) using quantum dot (QD) absorbers exhibit a larger design freedom than standard quantum well absorbers. The additional parameter of the dot density in combination with the field enhancement allows for an independent control of saturation fluence and modulation depth. We present the first detailed study of the effect of QD growth parameters and post growth annealing on the macroscopic optical SESAM parameters, measuring both nonlinear reflectivity and recombination dynamics. We studied a set of self-assembled InAs QD-SESAMs optimized for an operation wavelength around 960 nm with varying dot density and growth temperature. We confirm that the modulation depth is controlled by the dot density. We present design guidelines for QD-SESAMs with low saturation fluence and fast recovery, which are for example important for modelocking of vertical external cavity surface emitting lasers (VECSELs).
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