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610 results on '"Noginov, Mikhail A."'

2. Anomalous dips in reflection spectra of optical polymers deposited on plasmonic metals

Author

Shorter Ayanna, Chowdhury Md Golam Rabbani, Rout Sangeeta, and Noginov Mikhail A.

Subjects
optical polymers, plasmonic metals, reflection spectra, refractive indexes, scattering, surface plasmon polaritons, Physics, QC1-999
Abstract

We have studied reflection spectra of dye-doped and undoped polymers deposited onto Ag and Au substrates and found anomalous dips in the UV spectral range. On top of Ag substrates, the λ ∼ 375 nm dips were observed in undoped PMMA, PVP, and PS polymers as well as PMMA doped with Rh590 and HITC laser dyes. In silver-based samples, the spectral positions of the observed reflection dips were close to singularities in the refractive indexes of surface plasmon polaritons (SPPs) propagating at the interface between Ag and polymer. The latter singularities can tentatively explain the λ ∼ 375 nm reflection dips, if the scattering of Ag and polymeric films is large enough to launch SPP without any prism or grating. The dips observed in reflection of Rh590:PMMA and HITC:PMMA on top of Au, were more pronounced than those on Ag, broader, shifted to shorter wavelengths, and their spectral positions had large standard deviations. Furthermore, no anomalous dips in gold-based samples were observed in the reflection spectra of undoped PMMA, PVP, and PS polymers, and a modest singularity in the SPP refractive index, predicted theoretically at λ ∼ 500 nm, cannot explain the dips in the UV reflection spectra observed experimentally. It appears likely that the origin of the reflection dips on top of Au substrates is different from that on top of Ag substrates.

Published
2023
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3. Emission kinetics of HITC laser dye on top of arrays of Ag nanowires

Author

Rout Sangeeta, Peters Vanessa N., Pradhan Sangram K., Bonner Carl E., and Noginov Mikhail A.

Subjects
concentration quenching, emission kinetics, förster energy transfer, förster radius, silver nanowires, Physics, QC1-999
Abstract

We have grown arrays of silver nanowires in pores of anodic alumina membranes (metamaterials with hyperbolic dispersion at λ ≥ 615 nm), spin coated them with the dye-doped polymer (HITC:PMMA), and studied the rates of radiative and nonradiative relaxation as well as the concentration quenching (Förster energy transfer to acceptors). The results were compared to those obtained on top of planar Ag films and glass (control samples). The strong spatial inhomogeneity of emission kinetics recorded in different spots across the sample and strong inhibition of the concentration quenching in arrays of Ag nanowires are among the most significant findings of this study.

Published
2021
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4. Effect of nanoscale dielectric environments on concentration quenching

Author

Rout Sangeeta, Koutsares Samantha R., Courtwright Devon, Mills Ezekiel, Shorter Ayanna, Prayakarao Srujana, Bonner Carl E., and Noginov Mikhail A.

Subjects
concentration quenching, diffusion length, emission kinetics, förster radius, Physics, QC1-999
Abstract

We have studied the dependence of concentration quenching of luminescence (donor–acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d. This phenomenon is tentatively explained by a limited number of acceptors, which donors’ excitation can reach in thin samples, if the film’s thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (≥3 μm) HITC:PMMA films is cautiously attributed to the samples’ crystallinity.

Published
2021
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22. Control of F\'orster energy transfer in vicinity of metallic surfaces and hyperbolic metamaterials

Author

Tumkur, Thejaswi U., Kitur, John K., Bonner, Carl E., Poddubny, Alexander N., Narimanov, Evgenii E., and Noginov, Mikhail A.

Subjects
Physics - Optics
Abstract

Optical cavities, plasmonic structures, photonic band crystals, interfaces, as well as, generally speaking, any photonic media with homogeneous or spatially inhomogeneous dielectric permittivity (including metamaterials) have local densities of photonic states, which are different from that in vacuum. These modified density of states environments are known to control both the rate and angular distribution of spontaneous emission. In the present study, we ask the question whether the proximity to metallic and metamaterial surfaces can affect other physical phenomena of fundamental and practical importance. We show that the same substrates and the same nonlocal dielectric environments that boost spontaneous emission, also inhibit F\"orster energy transfer between donor and acceptor molecules doped into a thin polymeric film. This finding correlates with the fact that in dielectric media, the rate of spontaneous emission is proportional to the index of refraction n, while the rate of the donor-acceptor energy transfer (in solid solutions with random distribution of acceptors) is proportional to n^-1.5. This heuristic correspondence suggests that other classical and quantum phenomena, which in regular dielectric media depend on n, can also be controlled with custom-tailored metamaterials, plasmonic structures, and cavities., Comment: Faraday Discussions, FD 178, 2015, Advance Article

Published
2015
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26. Active metamaterials: sign of refraction index and gain-assisted dispersion management

Author

Govyadinov, Alexander A., Noginov, Mikhail A., and Podolskiy, Viktor A.

Subjects
Physics - Optics, Physics - General Physics
Abstract

We derive an approach to define the causal direction of the wavevector of modes in optical metamaterials, which in turn, determines signs of refractive index and impedance as a function of {\it real and imaginary} parts of dielectric permittivity and magnetic permeability. We use the developed technique to demonstrate that the interplay between resonant response of constituents of metamaterials can be used to achieve efficient dispersion management. Finally we demonstrate broadband dispersion-less index and impedance matching in active nanowire-based negative index materials. Our work opens new practical applications of negative index composites for broadband lensing, imaging, and pulse-routing.

Published
2007
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29. Additional Cover

Author

Visheratina, Anastasia, primary, Hesami, Leila, additional, Wilson, Ashleigh K., additional, Baalbaki, Nicole, additional, Noginova, Natalia, additional, Noginov, Mikhail A., additional, and Kotov, Nicholas A., additional

Published
2022
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30. Hydrothermal synthesis of chiral carbon dots

Author

Visheratina, Anastasia, primary, Hesami, Leila, additional, Wilson, Ashleigh K., additional, Baalbaki, Nicole, additional, Noginova, Natalia, additional, Noginov, Mikhail A., additional, and Kotov, Nicholas A., additional

Published
2022
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46. Effect of metal-dielectric environments on spontaneous emission and concentration quenching of HITC laser dye

Author

Rout, Sangeeta, primary, Koutsares, Samantha R., additional, Prayakarao, Srujana, additional, Courtwright, Devon, additional, Peters, Vanessa, additional, Qi, Zhen, additional, Petrosyan, Lyudvig S., additional, Shahbazyan, Tigran V., additional, Biener, Monika M., additional, Bonner, Carl E., additional, and Noginov, Mikhail A., additional

Published
2021
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