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Advanced Physical Research

TUNNELING EFFECT IN DOUBLE QUANTUM DOTS NANOSTRUCTURE

Wisam Roiss Matrood

Published Jun 4, 2024• 0 citations
Publisher

Abstract

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.

DOI
10.62476/apr62145

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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.
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.
With the presence of the signal pulse, a quantum dot (QD) four-level structure interacting with four fields forms a double-cascade configuration. The linear optical properties for amplification, absorption, and dispersion of two weak near-infrared (NIR) lights in this scheme are investigated. It shows that the amplification, transparency, normal and anomalous dispersion of the probe and signal fields, i.e., the two NIR waves, can be achieved by adjusting the relative phase of the applied lasers, the probe detuning, and the two pump Rabi energies appropriately, while when the signal pulse is removed, the nonlinear optical phenomenon four-wave mixing (FWM) originating from quantum interference is demonstrated. A highly efficient FWM process with a NIR mixing field generated can be realized in this system. Such investigation in a semiconductor QD system with flexible design and widely adjustable parameters may provide new possibilities for realizing the efficient generation and gain of NIR waves and manipulating light propagation between subluminal and superluminal in the solid-state materials.
Abstract Based on a GaAs/AlGaAs quadruple-coupled quantum dot heterostructure, an optical switch for controlling superluminal and subluminal light propagation is suggested. The transient and steady state behaviour of the absorption and dispersion of a probe pulse laser field through a quadruple quantum dot molecule are studied. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal, or vice versa, by controlling the tunnelling rates between the quantum dots. The required switching time is calculated and we find it to be about 8 ps. We also investigated a method for the all-optical switching of probe field absorption from a large amount to nearly zero just by applying an incoherent pumping field. We estimated the required switching time for this case to be between 3 and 14 ps.
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.
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 .