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Defect and diffusion forum/Diffusion and defect data, solid state data. Part A, Defect and diffusion forum

Phase and Amplitude Control of Optical Properties of Quantum Dot Molecules

Mohammad Mahmoudi, Sahar Goharshenasan

Published Apr 20, 2011• 1 citation
Publisher

Abstract

We investigate the optical properties of a weak probe field in an asymmetry semiconductor double QDs system. We apply a coupling and a probe field to the system and it is shown that in the presence of interdot tunneling, the dispersion and absorption properties of the system can be controlled by the amplitude and relative phase of applied fields. Moreover, it is demonstrated that just by changing the relative phase of applied fields, the slope of dispersion is changed from positive to negative, corresponding to the superluminal light propagation.

DOI
10.4028/www.scientific.net/ddf.312-315.172

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We investigate the optical properties of a weak probe field in an asymmetry semiconductor double QDs system. We apply a coupling and a probe field to the system and it is shown that in the presence of interdot tunneling, the dispersion and absorption properties of the system can be controlled by the amplitude and relative phase of applied fields. Moreover, it is demonstrated that just by changing the relative phase of applied fields, the slope of dispersion is changed from positive to negative, corresponding to the superluminal light propagation.
In this working, we introduce a Q-DD composed of two QDs. We find that the absorption and dispersion spectra of the light pulse can be changed via the effect of and inter-dot tunnel couplings and probe pumping field of QDs. Then, we employ the steady state and dynamical state in the four-level double QDs system. The slope of dispersion switches from positive to negative. Therefore, both superluminal and Subluminal light propagations can be achieved by simply applying a gate voltage to the double inter dot tunnel coupling. It is also demonstrated that by applying the indirect pump probe field to the probe transition the absorption-free superluminal light propagation is obtained. The results show that by proper tuning of the bias voltage. This structure also indicates that a wide range of linearity from negative to positive can be simply adjusted via a bias voltage, which would result in wide control of signal beam.
In this paper, the effect of relative phase of applied fields on probe field dispersion and absorption for a laddershaped three level quantum dot molecule is investigated. The results show that the relative phase of applied fields can be affected on the probe beam propagation, and thus its absorption, dispersion and group velocity. The dispersion and the absorption may change with the relative phase of applied fields. By adjusting relative phase of applied fields light propagation from superluminal to subluminal and absorption to gain can be switched.
We theoretically analyze the transient properties of a probe field absorption and dispersion in a coupled semiconductor double-quantum-dot nanostructure. We show that in the presence of the Gaussian laser beams, absorption and dispersion of the probe field can be dramatically influenced by the relative phase between applied fields and intensity of the Gaussian laser beams. Transient and steady-state behaviors of the probe field absorption and dispersion are discussed to estimate the required switching time. The estimated range is between 5–8 ps for subluminal to superluminal light propagation .
This letter investigates the dispersion and absorption properties of a weak probe field in a multiple quantum dot molecule composed of four quantum dots. It is found that, by manipulating the electric field, the inter-dot tunneling coupling and the laser detunings, the transparency window as well as the positive derivative in the refractive index can be efficiently qualified. It is shown that switching from positive to negative dispersion or vice versa can be achieved by changing the tunneling couplings. Moreover, we realize that the width and the number of transparency windows can be properly controlled by adjusting the system's parameters. We show that this multiple QD medium can experience very narrow transparency windows accompanied by very steep positive dispersions. The effect of an incoherent pumping field on the absorption–dispersion properties of the QD molecule is then discussed. We note that tunneling is used in this QD system instead of coupling lasers.