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Quantum Electronics

Phase control of group velocity of light in an InGaN/GaN quantum dot nanostructure

Hossein Jafarzadeh, Elnaz Ahmadi Sangachin, Seyyed Hossein Asadpour

Published Sep 28, 2015• 1 citation
Publisher

Abstract

By solving self-consistently Schrödinger – Poisson equations for a carrier in the conduction band of an InGaN/GaN quantum dot, a four-level quantum system is described. It is found that in the presence of terahertz signal radiation, the medium becomes phase dependent, which ensures the phase control of the group velocity of a weak probe pulse from slow to fast light.

DOI
10.1070/qe2015v045n09abeh015677

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By solving self-consistently Schrödinger – Poisson equations for a carrier in the conduction band of an InGaN/GaN quantum dot, a four-level quantum system is described. It is found that in the presence of terahertz signal radiation, the medium becomes phase dependent, which ensures the phase control of the group velocity of a weak probe pulse from slow to fast light.
Tunable phase control of the slow and fast light propagation through a defect slab medium doped by four-level InGaN/GaN quantum dot structure is demonstrated. By solving the Schrödinger and Poisson’s equations self-consistently, a spherical InGaN quantum dot with GaN barrier shell which can interact by terahertz (THz) signal field is designed numerically. It is found that the phase variation of THz signal field imparts the tunability in the group velocity of the transmitted and reflected pulses through a dielectric slab.
In this paper, we propose a novel scheme for controlling the group velocity of transmitted and reflected pulse from defect medium doped with four-level InGaN/GaN quantum dot nanostructure. Quantum dot nanostructure is designed numerically by Schrödinger and Poisson equations which solve self consistently. By size control of quantum dot and external voltage, one can design a four-level quantum dot with appropriate energy levels which can be suitable for controlling the group velocity of pulse transmission and reflection from defect slab with terahertz signal field. It is found that in the presence and absence of terahertz signal field the behaviors of transmission and reflection pulses are completely different. Moreover, it is shown that for strong terahertz signal field, by changing the thickness of the slab, simultaneous peak and dip for transmission and reflection pulse are obtained.
Abstract In this letter, we investigated the behaviors of the absorptive–dispersive properties of weak probe light in a four-level InGaN/GaN quantum dot nanostructure. In order to achieve the wave functions and their corresponding energy levels of the mentioned quantum dot nanostructure, Schrödinger and Poisson equations must be solved self consistently for carriers (here electrons) in quantum dots. The enhanced refractive index with amplification can be obtained via adjusting the corresponding controllable parameters such as intensity, detuning and relative phase of the applied fields. Our proposed scheme provides a realistic model for controlling the index of refraction in a quantum dot nanostructure.
In this paper, we proposed a model for controlling the group velocity of the transmitted and reflected pulses in a slab medium doped by four-level quantum dot nanostructure. Here, an infrared signal field interacted by quantum dot nanostructure can affect the behavior of reflected and transmitted pulses. We show that in the presence and absence of infrared pulses, the other controllable parameters have essential roles for controlling the slow and fast light propagation through the medium. Moreover, we found that the simultaneous slow and fast light can be obtained for the transmitted and reflected pulses by infrared signal field. Our proposed model may be useful for ultrahigh density optical memories in quantum communication systems or in various fields of all-optical systems.
In this paper, we investigated the transient electron population and the transient behaviour of the dispersion, absorption and refractive property of weak probe light in a four-level InGaN/GaN quantum dot nanostructure.In order to achieve the wave functions and their corresponding energy levels of the mentioned quantum dot nanostructure, the Schrödinger and Poisson equations is solved selfconsistently for carriers (here electron) in quantum dot.Our findings show that the properties of transient processes can be dramatically affected by parameters such as intensity, detuning and relative phase of applied fields.Our proposed scheme provides a realistic model for transient control of refraction index properties in a quantum dot nanostructure.These results may have potential applications in high speed optical switch for quantum information technologies.