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We investigate the optical properties appearing in a nanostructure that is composed of an asymmetric double semiconductor quantum dot (SQD) molecule and a metal nanoparticle (MNP). The profile of the total linear absorption spectrum is proportional to the SQD contribution, while the MNP contribution is important. The profile of the doublet of resonances detected on the total linear absorption spectrum creates a transparency window. The doublet is asymmetric for small SQD-MNP distances and has a narrow peak and a wide peak. The width of the transparency window is increased, either with the enhancement of the rate at which the electron tunneling effect takes place within the double SQD molecule or with the decrease of the distance that separates the SQD molecule from the center of the MNP. The steep slope detected on the linear dispersion spectrum for frequencies laying within the transparency window owes its presence to the tunneling induced transparency and leads to slow light production. The corresponding value of the slow down factor is maximized for low values of the electron tunneling rate as well as for low center-to-center distances between the components of the hybrid nanostructure. [ABSTRACT FROM AUTHOR]

The interaction of excitons with localized surface plasmons in hybrid nanostructures containing semiconductor quantum dots and metal nanoparticles, under specific conditions, may generate products with collective optical properties that have an abundance of potential applications in the area of nanotechnology. In the present study, we explore the behavior of the linear absorption and dispersion properties of the double-semiconductor quantum dot molecule in the presence of a spherical metal nanoparticle. We find that a transparency window arises in the absorption spectrum, the width of which decreases with the decrease in the electron tunnelling rate. In the low-electron-tunnelling regime, slow light is generated, an effect closely associated with tunneling-induced transparency. The enhancement of the tunneling rate induces a broadening in the transparency window, occurring due to the Autler–Townes splitting. The investigation of the impact of the distance between the quantum dot and the metal nanoparticle on the slowdown factor and the width of the transparency window shows that, by transposing the metal nanoparticle closer to the double-semiconductor quantum dot molecule, the transparency window widens. [ABSTRACT FROM AUTHOR]

In this study, we investigate the linear optical response in a hybrid nanostructure composed of a semiconductor quantum dot and a metal shell nanoparticle. We analyze a case wherein the nanostructure interacts with an incident electromagnetic field with polarization parallel to the symmetry axis of the nanosystem. We derive nonlinear density matrix equations in the rotating wave approximation under the quasistatic response of the system, and use a series expansion method to obtain analytical functions for linear susceptibility with respect to both components of the nanostructure. The imaginary part of these expressions is related to the absorption coefficient. We investigate the way in which the modification of the core's material affects the characteristics of the spectral resonance. For low values of the dielectric constant, the system exhibits amplified gain without population inversion and quenched absorption resonance, while for high values of the dielectric constant, we observe suppression of the gain dip and enhancement of the absorption resonance. In the first regime, the exciton lifetime is suppressed, and in the second case, its value is importantly increased, especially in the case of small interparticle distances where the semiconductor quantum dot and metal shell nanoparticle interact strongly. [ABSTRACT FROM AUTHOR]

We study optical effects in a hybrid system composed of a semiconductor quantum dot (SQD) and a spherical metal nanoparticle (MNP) that interacts with a weak probe and a strong pump electromagnetic field. We use modified nonlinear density matrix equations for the description of the optical properties of the system and calculate, numerically, the first-order susceptibilities of the SQD, the MNP, and the total hybrid nanostructure of the probe field in the presence of the pump field. We investigate the dependence of the probe absorption and dispersion spectra of the SQD, the MNP, and the total nanostructure on the interparticle distance and the detuning of the pump field, and stress the influence of the MNP contribution to the total optical response. The results we find are explained according to the theory of two distinct metastates, which constitute conjugations of the SQD excitonic and the MNP plasmonic excitations. We also show that the optical response strongly depends on the actual values of the SQD material parameters. [ABSTRACT FROM AUTHOR]

We study the four-wave mixing effect in a coupled semiconductor quantum dot-spherical metal nanoparticle structure. Depending on the values of the pump field intensity and frequency, we find that there is a critical distance that changes the form of the spectrum. Above this distance, the four-wave mixing spectrum shows an ordinary three-peaked form and the effect of controlling its magnitude by changing the interparticle distance can be obtained. Below this critical distance, the four-wave mixing spectrum becomes single-peaked; and as the interparticle distance decreases, the spectrum is strongly suppressed. The behavior of the system is explained using the effective Rabi frequency that creates plasmonic metaresonances in the hybrid structure. In addition, the behavior of the effective Rabi frequency is explained via an analytical solution of the density matrix equations. [ABSTRACT FROM AUTHOR]

We study theoretically the conditions under which optical bistability is achievable in a two-subband system in a semiconductor quantum well. We consider the interaction of the two-subband system with a continuous wave electromagnetic field, which induces intersubband transitions. For the description of the system dynamics we use the effective nonlinear density matrix equations. We solve these equations analytically, in the steady state, for a GaAs/AlGaAs quantum well structure. For several combinations of the values of the parameters three real solutions of the population inversion arise and the phenomenon of optical bistability prevails. [ABSTRACT FROM AUTHOR]

We study the linear and nonlinear optical response of intersubband transitions in a semiconductor quantum well. We describe the coupling of the quantum well structure with the electromagnetic field by using the nonlinear density matrix equations, in the two-subband approximation. We provide proper approximate analytical solutions to these equations that are used for the closed-form determination of the optical susceptibilities χ(1), χ(3), and χ(5). We also explore the dependence of χ(1), χ(3), and χ(5) on the electron sheet density for a specific double GaAs/AlGaAs quantum well. [ABSTRACT FROM AUTHOR]