We study optical effects in a hybrid system composed of a semiconductor quantum dot and a spherical metal nanoparticle that interacts with a weak probe electromagnetic field. We use modified nonlinear density matrix equations for the description of the optical properties of the system and obtain a closed-form expression for the linear susceptibilities of the quantum dot, the metal nanoparticle, and the total system. We then investigate the dependence of the susceptibility on the interparticle distance as well as on the material parameters of the hybrid system. We find that the susceptibility of the quantum dot exhibits optical transparency for specific frequencies. In addition, we show that there is a range of frequencies of the applied field for which the susceptibility of the semiconductor quantum dot leads to gain. This suggests that in such a hybrid system quantum coherence can reverse the course of energy transfer, allowing flow of energy from the metallic nanoparticle to the quantum dot. We also explore the susceptibility of the metal nanoparticle and show that it is strongly influenced by the presence of the quantum dot.

We theoretically study the optical properties of a hybrid nanostructure consisting of a metal nanoparticle and a semiconductor quantum dot. We derive a closed-form solution for the energy absorption spectra of the hybrid system and investigate the impact of the nonlocal dielectric response of a metal nanoparticle on the energy absorption. The results show significant modification when compared to those obtained with a local dielectric function. More specifically, the magnitude and shape of the energy absorption rate spectra are strongly modified, especially for small interparticle distances and high intensities of an external electric field interacting with the system.

Articles you may be interested inPrecise control of photoluminescence enhancement and quenching of semiconductor quantum dots using localized surface plasmons in metal nanoparticles Enhanced photorefractive effect in liquid crystal structures co-doped with semiconductor quantum dots and metallic nanoparticlesWe 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. V C 2014 AIP Publishing LLC. [http://dx.

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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.

The self-Kerr nonlinear optical response of a probe field is investigated in the presence of a near-resonant pump field in coupled metal nanoparticle (MNP)–semiconductor quantum dot (SQD) nanostructures. The study of the spectra is based on the solution of the resulted density matrix equations for the case of a colloidal CdSe-based SQD–(Au)­MNP molecule, as well as for an epitaxial SQD structure coupled to an Au nanoparticle. It is demonstrated that below a critical value of the interparticle distance the susceptibility of each distinct component of the structure exhibits a characteristic single-resonance spectrum, whereas above this value, the spectrum has three resonances. This phenomenon can be understood in terms of the theory of exciton–plasmon quantum metastates. In addition, the conditions under which optical transparency occurs with a concurrent positive self-phase-modulation coefficient are also identified.

There is considerable interest in collective effects in hybrid systems formed by molecular or atomic ensembles strongly coupled by an electromagnetic resonance. For analyzing such collective effects, we develop an efficient and general theoretical formalism based on the natural modes of the resonator. The main strength of our approach is its generality and the high level of analyticity enabled by modal analysis, which allows one to model complex hybrid systems without any restriction on the resonator shapes or material properties, and to perform statistical computations to predict general properties that are robust to spatial and polarization disorders. Most notably, we establish that superradiant modes remain even after ensemble averaging and act as an "invisibility cloak" with a spectral bandwidth that scales with the number of oscillators and the spatially-averaged Purcell factor. INTRODUCTIONCooperative scattering by large collections of quantum emitters has become increasingly important in modern science and technology, 1-3 an emblematic example being Dicke superradiance. 4 Of particular interest are high cooperativity regimes, which are promoted by long-range interactions and quantum cavity-electrodynamic effects with electromagnetic resonances. Recent exemplary advances encompass the generation of coherent visible radiation by many emitters placed near plasmonic nanoparticles 5-6 or hybrid quantum systems combining coldatom clouds with photonic-crystal resonances. [7][8] Even for steady-state cases, the theoretical analysis of quantum hybrids represents a major challenge in computational electrodynamics, requiring the repeated calculation of the full-photon Green's functions of the resonator for different frequencies and atomic positions. [9][10][11] The challenge worsens when studying the dynamics by iteratively solving coupled equations for the Maxwell's fields and carrier-population operators, [12][13] or when computing ensemble-averaged responses [14][15] to interpret experiments for which the exact location and orientation of atoms are unknown. [16][17][18] Here, we provide a powerful computational "toolkit" based on the natural modes of the resonator for analyzing collective effects in large ensembles of atoms or molecules coupled by an electromagnetic resonator, which could be a high-Q or low-Q micro-nanoresonator, possibly with a spectral overlap of several resonances. The main strength of our approach is the high level of analyticity brought on by the modal analysis of the emitterresonator interaction, which enables one to perform statistical treatments and to predict general properties that are robust to spatial and polarization disorders. We adopt a classical polarizability model for the quantum emitters. Classical-oscillator treatments cannot describe all aspects of quantum hybrids, but in return provide a rudimentary and intuitive tool, which is general enough to predict many important features of quantum systems and is reusable in quantum formalisms. [19][20][21][22]10 Additionally, cooperati...