The Experts below are selected from a list of 47565 Experts worldwide ranked by ideXlab platform
Mahi R. Singh - One of the best experts on this subject based on the ideXlab platform.
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Dipole–Dipole Interaction in Two-Photon Spectroscopy of Metallic Nanohybrids
The Journal of Physical Chemistry, 2020Co-Authors: Mahi R. Singh, Patrick D. PersaudAbstract:We have developed a theory for the two-photon fluorescence in nanohybrids made of an ensemble of metallic nanorod shells and an ensemble of quantum emitters. A metallic nanorod shell is made of a metallic rod and dielectric shell. We consider that the quantum emitters are four-level quantum systems. When a probe laser light falls on the metallic nanorod shells, the surface plasmon polariton electric field is produced at the interface between the metallic nanorod and dielectric shell. This electric field, along with the probe field, induces dipoles in the quantum emitters and nanorod shells. These dipoles interact with each other via the dipole–dipole Interaction. The two-photon fluorescence has been calculated by using the quantum density matrix method in the presence of the dipole–dipole Interaction (coupling). Analytical expressions of the two-photon fluorescence have been derived in the presence of the dipole–dipole Interaction. We showed that that the two-photon process is made of two terms. The first term is the two-photon process due to the two probe field photons. On other the hand, the second term is made of one DDI field photon and one probe field photon. It is found that the surface plasmon polariton resonance energy is not resonant with the exciton energy, the two-photon fluorescence spectrum splits from one peak to three peaks. The splitting in the spectrum is due to the presence of the dressed states created in the system due to the strong dipole–dipole Interaction. We also compared our theory with the experimental data of the metallic nanohybrid system made of metallic nanorod shells and quantum emitters (T790 molecules) and found a good agreement between the theory and the experiments.
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enhancement of the second harmonic generation in a quantum dot metallic nanoparticle hybrid system
Nanotechnology, 2013Co-Authors: Mahi R. SinghAbstract:We have investigated the second-harmonic generation (SHG) and dipole–dipole Interaction in a quantum dot and metallic nanoparticle hybrid system. A strong probe field is applied to create two-photon absorption in the quantum dot and metallic nanoparticle. SHG photons and SHG surface plasmon polaritons are emitted by the quantum dot and metallic nanoparticle, respectively. Induced dipoles are created in the quantum dot and the metallic nanoparticle due to two-photon absorption and hence both systems interact with each other via the dipole–dipole Interaction. It is found that SHG signals produced by the quantum dot and nanoparticle are enhanced by the dipole–dipole Interaction and also that the SHG signal can be switched on and off by applying a control field. The theoretical findings of this paper are supported by recent experimental studies. The present hybrid system can be used to fabricate nano-sensors and all-optical nano-switching devices.
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Dipole-Dipole Interaction between a quantum dot and a graphene nanodisk
Physical Review B, 2012Co-Authors: Joel D. Cox, Mahi R. Singh, Godfrey Gumbs, Miguel A. Antón, Fernando CarreñoAbstract:We study theoretically the Dipole-Dipole Interaction and energy transfer in a hybrid system consisting of a quantum dot and graphene nanodisk embedded in a nonlinear photonic crystal. In our model, a probe laser field is applied to measure the energy transfer between the quantum dot and graphene nanodisk, while a control field manipulates the energy transfer process. These fields create excitons in the quantum dot and surface plasmon polaritons in the graphene nanodisk which interact via the Dipole-Dipole Interaction. Here, the nonlinear photonic crystal acts as a tunable photonic reservoir for the quantum dot, and is used to control the energy transfer. We have found that the spectrum of power absorption in the quantum dot has two peaks due to the creation of two dressed excitons in the presence of the Dipole-Dipole Interaction. The energy transfer rate spectrum of the graphene nanodisk also has two peaks due to the absorption of these two dressed excitons. Additionally, energy transfer between the quantum dot and the graphene nanodisk can be switched on and off by applying a pump laser to the photonic crystal or by adjusting the strength of the Dipole-Dipole Interaction. We show that the intensity and frequencies of the peaks in the energy transfer rate spectra can be modified by changing the number of graphene monolayers in the nanodisk or the separation between the quantum dot and graphene. Our results agree with existing experiments on a qualitative basis. The principle of our system can be employed to fabricate nanobiosensors, optical nanoswitches, and energy transfer devices.
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dipole dipole Interaction in a quantum dot and metallic nanorod hybrid system
Applied Physics Letters, 2011Co-Authors: Mahi R. Singh, Daniel Schindel, Ali HatefAbstract:We have studied quantum coherence and interference phenomena in a quantum dot (QD)-metallic nanorod (MNR) hybrid system. Probe and control laser fields are applied to the hybrid system. Induced dipole moments are created in the QD and the MNR, and they interact with each other via the Dipole-Dipole Interaction. Using the density matrix method, it was found that the power spectrum of MNR has two transparent, states and they can be switched to one transparent state by the control field. Ultrafast switching and sensing nanodevices could be produced using this model.
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Simulations of Dipole‐Dipole Interaction in Nonlinear Photonic Crystals Doped With Nanoparticles
AIP Conference Proceedings, 2008Co-Authors: Mahi R. SinghAbstract:We have performed numerical simulations on the dipole‐dipole Interaction in a nonlinear photonic crystal doped with nanoparticles. A pump field is applied to change the refractive index of the crystal. It is found that as the intensity of the pump field increases the crystal goes from absorption state to the transparent state and remains in the later state. The present mechanism can be used to makes optical switches, optical memory, optical transistor, optical discriminator, optical limiter, optical oscillator, optical gate etc.
Tilman Pfau - One of the best experts on this subject based on the ideXlab platform.
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Probing the light-induced Dipole-Dipole Interaction in momentum space
EPL, 2005Co-Authors: Rudolf Gati, Jürgen Stuhler, Tilman PfauAbstract:We theoretically investigate the mechanical effect of the light-induced Dipole-Dipole Interaction potential on the atoms in a Bose-Einstein condensate. We present numerical calculations on the magnitude and shape of the induced potentials for different experimentally accessible geometries. It is shown that the mechanical effect can be distinguished from the effect of incoherent scattering for an experimentally feasible setting.
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Observation of Dipole-Dipole Interaction in a degenerate quantum gas
Physical Review Letters, 2005Co-Authors: Jürgen Stuhler, Tilman Pfau, A. Griesmaier, T. Koch, M. Fattori, S. Giovanazzi, P. Pedri, L. SantosAbstract:We have investigated the expansion of a Bose-Einstein condensate (BEC) of strongly magnetic chromium atoms. The long-range and anisotropic magnetic Dipole-Dipole Interaction leads to an anisotropic deformation of the expanding Cr-BEC which depends on the orientation of the atomic dipole moments. Our measurements are consistent with the theory of dipolar quantum gases and show that a Cr-BEC is an excellent model system to study dipolar Interactions in such gases.
Jürgen Stuhler - One of the best experts on this subject based on the ideXlab platform.
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Probing the light-induced Dipole-Dipole Interaction in momentum space
EPL, 2005Co-Authors: Rudolf Gati, Jürgen Stuhler, Tilman PfauAbstract:We theoretically investigate the mechanical effect of the light-induced Dipole-Dipole Interaction potential on the atoms in a Bose-Einstein condensate. We present numerical calculations on the magnitude and shape of the induced potentials for different experimentally accessible geometries. It is shown that the mechanical effect can be distinguished from the effect of incoherent scattering for an experimentally feasible setting.
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Observation of Dipole-Dipole Interaction in a degenerate quantum gas
Physical Review Letters, 2005Co-Authors: Jürgen Stuhler, Tilman Pfau, A. Griesmaier, T. Koch, M. Fattori, S. Giovanazzi, P. Pedri, L. SantosAbstract:We have investigated the expansion of a Bose-Einstein condensate (BEC) of strongly magnetic chromium atoms. The long-range and anisotropic magnetic Dipole-Dipole Interaction leads to an anisotropic deformation of the expanding Cr-BEC which depends on the orientation of the atomic dipole moments. Our measurements are consistent with the theory of dipolar quantum gases and show that a Cr-BEC is an excellent model system to study dipolar Interactions in such gases.
Ad Lagendijk - One of the best experts on this subject based on the ideXlab platform.
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Resonantly induced Dipole-Dipole Interactions in the diffusion of scalar waves.
Physical Review B, 1994Co-Authors: B. A. Van Tiggelen, Ad LagendijkAbstract:The induced Dipole-Dipole Interaction can be understood in terms of recurrent elastic scattering of waves. We implement this notion into transport theory of scalar waves in inhomogeneous dielectric media and calculate rigorously the pivotal cooperative effect of pairs of polarizable dipoles.
Girish S. Agarwal - One of the best experts on this subject based on the ideXlab platform.
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Monitoring the Dipole-Dipole Interaction via Quantum Jumps of Individual Atoms
Physical Review A, 2001Co-Authors: C. Skornia, Girish S. Agarwal, J. Von Zanthier, E. Werner, Herbert WaltherAbstract:The emission characteristics in the fluorescence of two laser-driven Dipole-Dipole-interacting three-level atoms is investigated. When the light from both atoms is detected separately a correlation of the emission processes is observed in dependence of the Dipole-Dipole Interaction. This opens the possibility to investigate the Dipole-Dipole Interaction through the emission behavior. We present quantum Monte Carlo simulations which are in good agreement with the analytic solutions.
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Microcavity-induced modification of the Dipole-Dipole Interaction
Physical Review A, 1998Co-Authors: Girish S. Agarwal, S. Dutta GuptaAbstract:We consider the feasibility of controlling the energy transfer between an unexcited and an excited atom using microcavities. The excitation-transfer probability is related to the strength of the Dipole-Dipole Interaction and thus the excitation-transfer rates could be increased by enhancing the Dipole-Dipole Interaction. We demonstrate this enhancement with an explicit three-dimensional calculation for a metallic cavity, which we characterize with a realistic dielectric function. We also demonstrate the shifts in cavity resonances from their ideal positions mλ/2 (m is an integer and λ is the wavelength).