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.
In this paper, we perform a finite element (FE)-based numerical analysis to calculate the photoacoustic (PA) signal generated by spherical gold-silver (Au-Ag) alloy nanoparticles (NPs). These spherical particles are size-controlled and monodispersed, with tunable plasmonic resonance wavelength via change of the alloy composition. This enables their use in photoacoustic imaging as a contrast agent. This theoretical framework self consistently solves the electromagnetic, thermodynamic and transient acoustic pressure physics using a multiphysics coupling approach. We model our system as an optically heterogeneous medium irradiated by a nanosecond laser pulse in the tissue therapeutic optical window (NIR irradiation, with wavelength of 800 nm). We calculate the photoacoustic signal generated by the photo-thermal expansion of both the particle and its surrounding medium. The results show the impact of the gold molar fraction (GMF) of Au-Ag alloy NPs on the PA signal for different NP sizes. We show that significantly stronger PA signals are achieved using Au-Ag alloy NPs (GMF = 0.55) in comparison with pure AuNPs (GMF = 1) and pure AgNPs (GMF = 0) of the same size and shape.
We study the variation of the energy absorption rate in a hybrid semiconductor quantum dot-metallic nanoparticle system doped in a photonic crystal. The quantum dot is taken as a three-level V-configuration system and is driven by two applied fields (probe and control). We consider that one of the excitonic resonance frequencies is near to the plasmonic resonance frequency of the metallic nanoparticle, and is driven by the probe field. The other excitonic resonance frequency is far from both the plasmonic resonance frequency and the photonic bandgap edge, and is driven by the control field. In the absence of the photonic crystal we found that the system supports three excitonic-induced transparencies in the energy absorption spectrum of the metallic nanoparticle. We show that the photonic crystal allows us to manipulate the frequencies of such excitonic-induced transparencies and the amplitude of the energy absorption rate.
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