Nanocrystalline perovskite N dF eO 3 with the orthorhombic structure was prepared by a glycine nitrate combustion method under different technological conditions. The starting materials F e(N O 3 ) 3 · 9H 2 O, N d(N O 3 ) 3 · 6H 2 O in stoichiometric amounts and H 2 N CH 2 COOH were used. These quantities were varied by changing the ratio of glycine moles to metal nitrate moles (G/N) in the range between 0.25 to 0.75. The prepared N dF eO 3 nanocrystals were characterized by X-ray diffraction (XRD) and electron microscopy. Decomposition of the XRD diffraction profile using Voigt contours was exploited for analysis of the pattern in the area where the most prominent diffraction peak was situated. We demonstrate that Voigt functions reduce to Lorentzians for G/N =0.75 and 0.56. A volume-weighted diameter distribution function was derived using the width of the Lorentzians. The log-normal shape of the distribution is discussed in terms of the model, assuming exponential growth of cluster size in the time available for the N dF eO 3 nanograin to grow.
A theory of the two-photon florescence for a metallic nanoshell in the presence of quantum emitters has been developed. The metallic nanoshell is made of a metallic nanosphere as a core and a dielectric material as a shell. An ensemble of quantum emitters is deposited on the surface of the dielectric shell. A probe field is applied to study the two-photon process in the metallic nanoshell. Surface plasmon polaritons are created at the interface between the core and shell due to coupling between probe photons and surface plasmons present at the surface of the metallic nanosphere. The intensity of the surface plasmon polariton field is huge when the probe photon energy is in resonance with the polariton resonance energy. Induced electric dipoles are created in each quantum emitter due to the surface plasmon polariton field and the probe field. Dipoles in quantum emitters interact with each other via the dipole-dipole interaction. The dipole-dipole interaction is calculated using the many-body theory and mean field approximation. It is found that the dipole-dipole interaction has new term which is induced by the surface plasmon polariton field. An analytical expression of the two-photon florescence is derived in the presence the dipole-dipole interaction. Our theory predicts that the intensity of the two-photon florescence is enhanced in the presence of quantum emitters relative to the florescence of the metallic nanoshell in isolation. Physics behind the enhancement is the presence of the dipole-dipole interaction between the ensemble of quantum emitters. It is also found that as the concentration of quantum emitters increases, the dipole-dipole field also increases. This in turn, increases the two-photon florescence as function of the concentration. Finally, we have compared our theory with experiments of a metallic nanoshell which is made for Au nanosphere core and the SiO 2 shell. The metallic nanoshell is surrounded by various concentrations of Cadmium-Selenium quantum dots as quantum emitters. A good agreement between theory and experiment is found.
A theory of a switching and sensing mechanisms using the Kerr nonlinearity has been developed for nanohybrids made of an ensemble of three-level quantum emitters and metallic nanoshells. We have calculated the surface plasmon polaritons at interface between the metallic core and dielectric shell of the metallic nanoshell. The Kerr nonlinearity has been calculated by using the quantum density matrix method in the dipole–dipole coupling between quantum emitters. We showed that the switching and sensing mechanisms due to the Kerr nonlinearity are made of four contributions. The first contribution is due to three probe photons and the second one is due to one polariton and two probe photons. On other hand, the third contribution is due to the two polaritons and one probe photon, and the fourth one is due to three polaritons. The enhancement in the Kerr nonlinearity is found, and it is due to second, third, and fourth contributions. This prediction can be used to fabricate all optical Kerr nanosensors. It is also shown that two peaks (ON) in the Kerr coefficient can be switched to four peaks (OFF) due to the strong dipole–dipole coupling. We have also predicted that the Kerr coefficient can be switched from the positive value (ON) to the negative value (OFF) by changing the dipole–dipole coupling. We found that the minimum of the Kerr coefficient changes sign from positive (ON) to negative (OFF) as the dipole–dipole coupling strength increases. The splitting in the Kerr spectrum is due to the presence of the dressed states created in the nanohybrid due the dipole–dipole interaction. These predictions can be used to fabricate all optical Kerr nanoswitches.
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