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Laser Physics

Pulse propagation through a dielectric slab doped with a triple quantum dot nanostructure

Rajab Nasehi, Mohammad Mahmoudi, Mostafa Sahrai

Published Sep 20, 2016• 6 citations
Publisher

Abstract

Abstract The propagation of an electromagnetic pulse through a dielectric slab doped with a triple quantum dot (QD) nanostructure has been discussed in the presence of electron tunneling. We include the effect of an incoherent pump field in the transmission and reflection of a pulse in a triple QD. It is shown that the reflected and transmitted pulses can be switched from subluminal to superluminal light propagation by changing either the rate of the incoherent pump field or the inter-dot tunneling between QD1, QD2 and QD3 in a slab. Furthermore, it is demonstrated that the inter-dot tunnel coupling can significantly affect the behavior of optical bistability (OB) and optical multi-stability (OM) in a dielectric slab. The obtained results can be used for the development of new types of nanoelectronic devices for realizing the switching process.

DOI
10.1088/1054-660x/26/11/115202

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Abstract The propagation of an electromagnetic pulse through a dielectric slab doped with a triple quantum dot (QD) nanostructure has been discussed in the presence of electron tunneling. We include the effect of an incoherent pump field in the transmission and reflection of a pulse in a triple QD. It is shown that the reflected and transmitted pulses can be switched from subluminal to superluminal light propagation by changing either the rate of the incoherent pump field or the inter-dot tunneling between QD1, QD2 and QD3 in a slab. Furthermore, it is demonstrated that the inter-dot tunnel coupling can significantly affect the behavior of optical bistability (OB) and optical multi-stability (OM) in a dielectric slab. The obtained results can be used for the development of new types of nanoelectronic devices for realizing the switching process.
The optical bistability (OB) behavior of a dielectric slab doped with quantum dot (QD) molecules is investigated in the presence of the inter-dot tunneling effect. It is shown that the threshold point of OB reduces by increasing inter-dot tunneling as well as by reducing the slab thickness. It is worth noting that the threshold of OB in a slab doped with QD molecules is smaller, by at least one order of magnitude, in respect to free QD molecules. We find that the inter-dot tunneling induces a negative group delay to the reflected pulse and it propagates in the superluminal region. Such simple control can be used in all optical switching.
A switch is proposed for controlling the subluminal and superluminal light propagation through the triple coupled quantum dots system. The steady-state and transient behavior of the absorption and the dispersion of a probe pulse through a triple quantum dots molecule are investigated. We demonstrate that the group velocity of a light pulse can be controlled from subluminal to superluminal or vice versa by controlling the rates of incoherent pumping and tunneling between electronic levels. Switching time is calculated by discussing the dependency of optical transient properties on the incoherent pumping and inter-dot tunneling rates. We introduce three controlling parameters that make it possible to control the wave propagation electrically or even optically in such coupled quantum dot systems.
Propagation of an electromagnetic pulse through a dielectric slab doped with three-level ladder-type atomic systems is discussed. It is shown that the group velocity of the reflected and transmitted pulses can be switched from subluminal to superluminal light propagation by the thickness of the slab or the intensity of the coupling field. Furthermore, it is found that, in the presence of quantum interference, the reflected and transmitted pulses are completely phase dependent. So, the group velocity of the reflected and transmitted pulses can only be switched from subluminal to superluminal by adjusting the relative phase of the applied fields.
In this paper, optical bistability (OB) and multistability (OM) properties of a defect dielectric slab are studied. A GsAs multiple quantum well nanostructure (MQW) with 17.5 nm GaAs wells and 15 nm Al(0.3) Ga(0.7) barriers is used in the dielectric medium as a defect layer. Therefore, properties of the refractive index of the slab can be changed in the presence of MQWs. It is observed that switching from OB to OM can be obtained by controlling some external parameters. We find that the exciton spin relaxation and thickness of the slab have essential roles in adjusting the OB and OM properties of the probe light through the slab. Moreover, transmission, reflection, and absorption properties of the propagating pulse through the slab are also discussed. We show that the subluminal and superluminal light transmission or reflection can be obtained via amplification of the probe pulse through the medium. We hope that our proposed model may be suitable for the development of nanoscale devices in all-optical quantum information technology.
Abstract In this paper, we have proposed a new model based on the electron tunneling effect for controlling the optical bistability (OB) and optical multistability (OM) in a defect slab structure with a quantum dot molecule (QDM). Due to the presence of the electron tunneling effect, an additional weak signal beam can be generated in the system which makes the medium becomes phase dependent. We have studied the refractive index properties of the QDM via optical susceptibility of the propagated probe light. We have discussed the relative phase effect on negative refractive index (NRI) of the QDM nanostructure due to presence of electron tunneling. Then, by using the transfer matrix method, we have studied the transmission coefficient for NRI of the QDM nanostructure. Then, we have investigated the properties of transmitted light versus incident light for realizing the OB and OM. We have considered the relative phase effect on OB and OM properties of the transmitted beam and find that the switching between them is possible when electron tunneling is present in the quantum dot. Moreover, the optical thickness of the defect layer is also investigated on OB and OM in resonance and non-resonance conditions.