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Chinese Physics Letters

Phase Control of Transient Optical Properties of Double Coupled Quantum-Dot Nanostructure via Gaussian Laser Beams

Jalil Shiri, Fatemeh Shahi, Mohammad Reza Mehmannavaz, Laya Shahrassai

Published Feb 1, 2018• 6 citations
Publisher

Abstract

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 .

DOI
10.1088/0256-307x/35/2/024204

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The transient and steady-state behavior of the absorption and the dispersion of a probe pulse laser field propagating through an InGaAs\InP double coupled quantum well are studied. The effect of terahertz radiation excitation, electron tunnelling and incoherent pumping on the optical properties of the probe field is discussed. In the terahertz (30~300 μm or 1~10 THz) intersubband transition, the incoming photon energy is (4~41 mev) and maybe in the order of electron thermal broadening (KT~6 meV-25 meV for 77 K-300 K). Therefore in the conventional structure, the incoming photon can directly excite the ground state electrons to higher energy levels and this process inhabits the correct optical switching in terahertz applications. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal or vice versa by controlling the rates of incoherent pumping field and tunnelling between the quantum wells. The required switching time is calculated and we find it between 3 to 26 picoseconds.

Journal of Lasers Optics & Photonics•Jan 1, 2017•1 citation
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 .
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.
The problem of pulse propagation is theoretically investigated through a coupled semiconductor-double-quantum-dot (SDQD) nanostructure. Solving the coupled Maxwell–Bloch equations for the SDQD and field simultaneously, the dynamic control of pulse propagation through the medium is numerically explored. It is found that when all the control fields are in exact resonance with their corresponding transitions, a weak Gaussian-shaped probe pulse is transmitted through the medium nearly without any significant absorption and losses so that it can preserve its shape for quite a long propagation distance. In contrast, when one of the control fields is not in resonance with its corresponding transition, the probe pulse will be absorbed by the QD medium after a short distance. Then we consider the probe pulses with higher intensities. It is realized that an intense probe pulse experiences remarkable absorption and broadening during propagation. Finally, we demonstrate that this SDQD system can be employed as an optically controllable switch for the wave propagation to transit from an absorbing phase to a perfect transparency for the probe field. The required time for such switch is also estimated through realistic values.
The transient and steady-state behaviour of the absorption and the dispersion of a probe field propagating at λ = 1.55 μm through an InGaAs\InP double coupled quantum well are studied. The effect of terahertz signal excitation, electron tunnelling and incoherent pumping on the optical properties of the probe field is discussed. The linear dynamical properties of the double coupled quantum well by means of perturbation theory and density matrix method are discussed. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal or vice versa by controlling the rates of incoherent pumping field, terahertz signal and tunnelling between the quantum wells. The required switching time is calculated and we find it between 3 to 15 ps. In the terahertz (30 ~ 300 μm or 1 ~ 10THz) intersubband transition, the incoming photon energy is (4 ~ 41mev) and maybe in the order of electron thermal broadening (KT ~ 6 meV-25 meV for 77 K -300 K). Therefore in the conventional structure, the incoming photon can directly excite the ground state electrons to higher energy levels. It is shown that the absorption and the dispersion of the probe field can be controlled by the intensity of terahertz signal and incoherent pumping field.
The transient and steady-state behavior of the absorption and the dispersion of a probe pulse laser field propagating through an InGaAs\InP double coupled quantum well are studied. The effect of terahertz radiation excitation, electron tunnelling and incoherent pumping on the optical properties of the probe field is discussed. In the terahertz (30~300 μm or 1~10 THz) intersubband transition, the incoming photon energy is (4~41 mev) and maybe in the order of electron thermal broadening (KT~6 meV-25 meV for 77 K-300 K). Therefore in the conventional structure, the incoming photon can directly excite the ground state electrons to higher energy levels and this process inhabits the correct optical switching in terahertz applications. We show that the group velocity of a light pulse can be controlled from superluminal to subluminal or vice versa by controlling the rates of incoherent pumping field and tunnelling between the quantum wells. The required switching time is calculated and we find it between 3 to 26 picoseconds.