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Optics Letters

Enhancing slow- and fast-light effects in quantum-dot semiconductor waveguides through ultrafast dynamics

Yaohui Chen, Jesper Mørk

Published Feb 23, 2010• 9 citations
Publisher

Abstract

We show that ultrafast carrier dynamics plays an important role on slow- and fast-light effects based on coherent population oscillations in quantum-dot semiconductor waveguides. Fast light in the gain regime and slow light in the absorption regime are found to be enhanced at frequencies beyond the usual limits of the carrier lifetime. The effects are investigated by a comprehensive model and are shown to originate from nonequilibrium dynamics within the quantum-dot carrier populations.

DOI
10.1364/ol.35.000697

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We show that ultrafast carrier dynamics plays an important role on slow- and fast-light effects based on coherent population oscillations in quantum-dot semiconductor waveguides. Fast light in the gain regime and slow light in the absorption regime are found to be enhanced at frequencies beyond the usual limits of the carrier lifetime. The effects are investigated by a comprehensive model and are shown to originate from nonequilibrium dynamics within the quantum-dot carrier populations.
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Coherent population oscillations (CPO) in quantum dots (QDs) have been utilized in this article to achieve slow and fast light effects in a semiconductor optical amplifier. These phenomena have been achieved based on a pump-probe scheme and tuning the input current source. Coupled rate equations have been developed to determine the carrier dynamics and occupation probabilities. The effects of barrier, wetting layer and excited state densities have been included for CPO phenomenon occurring between the ground states. A quantum disc model embedded in another disc has been assumed for modeling the QDs and density matrix elements are used to obtain induced polarization at the signal frequency after determining the energy states and state probabilities. Tunable absorption dip, corresponding refractive index variation and group index, exhibit widely tunable slow and fast light characteristics by changing the bias condition.