General analytical expressions are derived for the light pressure force that acts on a spherical particle of arbitrary size and material composition (dielectric, metal) located in the interference field of two arbitrary monochromatic vector Bessel beams. For identical beams on orders of m = 0 and 1, the light pressure force is examined for the case of two parallel and copropagating beams and the case of intersection of the beam axes near a dielectric particle. It is shown that the presence of interference leads to a complex motion of a particle located in a plane perpendicular to the parallel beams. It is also demonstrated that with a change in the angle formed by the intersection of the axes of Bessel beams in the center of the particle, the light pressure force changes nonmonotonically, passing through maxima and minima, the number of which increases with increasing particle size. When the particle is displaced from the intersection point of the axes along a straight line located symmetrically between the beams, the light pressure force oscillates with a change in sign and with a gradually decreasing amplitude.

The light pressure of an evanescent electromagnetic wave formed by total internal reflection near the flat interface of a dielectric and a liquid on a dielectric spherical nanoparticle located in a liquid medium is considered. Phase portraits of a two-dimensional system of equations that is equivalent to the equation of nanoparticle transportation under the influence of the force gradient of the light pressure of the evanescent field taking into account the medium resistance force are plotted. Various phase portraits can be realized both without equilibrium points and with one equilibrium point (stable focus, stable node or saddle) on the phase plane, depending on the parameters of the laser radiation and the material of the nanoparticle suspended in the water.

With the help of the original mathematical method for solving Maxwell’s equations, it is shown that in dielectric waveguides along with usual waveguides and quasi-normal modes, there are perfect invisibility modes or perfect non-scattering modes. In contrast to the usual waveguide modes, at eigenfrequencies of the perfect invisibility modes, light can propagate in free space. The properties of the invisibility modes in waveguides of circular and elliptical cross-sections are analyzed in detail. It is shown that at the eigenfrequencies of the perfect invisibility modes, the power of the light scattered from the waveguide tends to zero and the optical fiber becomes invisible. The found modes can be used to create highly sensitive nanosensors and other optical nanodevices, where radiation and scattering losses should be minimal.

General analytical expressions for the light pressure force acting on a spherical particle placed in the field of the Bessel beam have been derived. It has been shown that an attractive force may arise in the first-order beam if both the dielectric permittivity and magnetic permeability of the particle are positive or negative. For an off-axis particle, it has been found that it may execute eddy motion in the cross-sectional area of the beam, both approaching the axis and moving away from it.

Plasma supports electromagnetic waves propagation for frequencies higher than plasma frequency but features dielectric permittivity less than 1. This property leads to photon density of states (DOS) lower than in vacuum and should result in subnatural spectral linewidths, sub-Planckian spectrum of thermal radiation, and sub-Rayleigh scattering as well as in lower inelastic photon scattering including Raman scattering. Lamb shift will be altered as well though the decisive contribution from high-energy modes in this case makes the photon DOS effect rather small since plasma DOS converges with the vacuum one in the limit of infinite frequencies. We emphasize the basic character of all these phenomena though absolute values of corrections in many real experiments may appear to be small as compared to other factors. We found that dissipative losses make possible DOS effects smaller though not vanishing and additionally bring about indefinite growth of DOS in the low-frequency limit.

In metal–dielectric nanostructures with metal inhomogeneities of about 10–100 nm in size strong local concentration of electromagnetic radiation at the frequencies of the incident (primary) and emitted (secondary) radiation occurs simultaneously with a considerable increase of the rate of nonradiative transitions (fluorescence quenching). The general principles of the use of metal–dielectric nanostructures to enhance the fluorescence and the experimental use of these principles for organic molecules, including biomolecules with fluorescent labels, are examined.

Aluminum nanoparticles attract scientific interest as a promising low-cost material with strong plasmon resonance in the ultraviolet region, which can be used in various fields of photonics. In this paper, for the first time, ultraviolet luminescence of zinc oxide nanoparticles in colloid solutions and nanostructure films in the presence of plasmonic aluminum nanoparticles 60 nm in size with a metal core and an aluminum oxide shell were studied. Mixture colloids of ZnO and Al nanoparticles in isopropyl alcohol solution with concentrations from 0.022 to 0.44 g/L and 0.057 to 0.00285 g/L, correspondingly, were investigated. The enhancement of up to 300% of ZnO emission at 377 nm in colloids mixtures with metal nanoparticles due to formation of Al-ZnO complex agglomerates was achieved. Plasmon nanostructures with different configurations of layers, such as Al on the surface of ZnO, ZnO on Al, sandwich-like structure and samples prepared from a colloidal mixture of ZnO and Al nanoparticles, were fabricated by microplotter printing. We demonstrated that photoluminescence can be boosted 2.4-fold in nanostructures prepared from a colloidal mixture of ZnO and Al nanoparticles, whereas the sandwich-like structure gave only 1.1 times the amplification of luminescence. Calculated theoretical models of photoluminescence enhancement of ideal and weak emitters near aluminum nanoparticles of different sizes showed comparable results with the obtained experimental data.

Metallic or dielectric nano-objects change the photon local density of states of closely placed emitters, particularly when plasmon or Mie resonances are present. Depending on the shape and material of these nano-objects, they may induce either a decrease or an increase in decay rates of the excited states of the emitter. In this work, we consider the reduction of the probability of optical transitions in emitters near high-refractive index dielectric (silicon and zinc selenide) nanoparticles. We tune the spectral positions of magnetic and electric modes of nanocylinders to obtain the largest overlap of the valleys in the total decay rate spectra for differently oriented dipoles and, in this way, find the highest inhibition of about 80% for randomly oriented emitters. The spectral positions of these valleys are easy to control since the wavelengths of the modes depend on the height and diameter of nanocylinders. The inhibition value is robust to the distance between the emitter and the nanoparticle in the range of nearly 50 nm, which is crucially important for the applications, such as selective optical transition engineering and photovoltaics.

The existence of an infinite number of perfect nonradiating modes in elliptical nanofibers is demonstrated. Dispersion laws are found for TM and TE perfect modes in circular and elliptical waveguides with an arbitrary eccentricity. Numerical simulations in Comsol Multiphysics have shown that these modes can be excited by plane waves of a certain parity and have extremely low radiative losses and extremely high quality factors. The found modes can be used to create highly sensitive nanosensors and other optical nanodevices where radiation losses should be minimal.

The effect of gold and silver plasmonic films on the photoluminescence and photostability of InP/ZnSe/ZnSeS/ZnS nanocrystals (quantum dots) is reported. Colloidal gold films promote the photostability enhancement of InP/ZnSe/ZnSeS/ZnS quantum dots (more durable emission properties in the presence of metal nanostructures) through reducing exciton lifetime. In contrast, silver decreases the photostability of InP/ZnSe/ZnSeS/ZnS quantum dots without changing the photoluminescence intensity and kinetics. By adjusting the excitation wavelength closer to the extinction band of gold nanoparticles a 1.8-fold enhancement of luminescence intensity has been obtained using a polyelectrolyte spacer between the metal and InP/ZnSe/ZnSeS/ZnS nanoparticles. Thus, plasmonics offers essential practical improvement of light emitters in terms of their durable luminescent properties upon prolonged optical excitation without losses in luminescence efficiency or even along with increased efficiency.

The spectra of light reflection by plasmonic metal films deposited in vacuum on dielectric substrates and subsequently annealed at high temperatures are investigated. To explain the optical properties of plasmonic films, a theoretical model of a flat-layered metal-dielectric medium is used. One of the layers of such a structure has the dielectric constant of the metal under study, and the second layer has the dielectric constant calculated within the Maxwell-Garnett approximation for a heterogeneous medium consisting of a suspension of metallic nanoellipsoids in air. The introduction of this layer makes it possible to qualitatively take into account the inhomogeneities of the plasmonic film surface. It is shown that the developed model makes it possible to explain a number of features in the experimental reflection spectra

Abstract We examined systematically how self-assembled monolayers (SAMs) of different mercaptoacids affect the spectral shift of the localized surface plasmon resonance in silver nanoplates and nanospheres. We observed a clear trend in the magnitude of a redshift with a molecular length or the SAM thickness within a homologous series of aliphatic mercaptoacids: the thicker shell the stronger the red shift. Using classic Mie theory for plasmonic core-dielectric shell spheres and oblate spheroids we developed the method for determination of a pseudo-refractive index in SAM of different molecules and obtained a good correlation with the reference refractive indices for bulk long-chain aliphatic acids, but only in case of silver nanoplates. Calculations for silver core–shell nanospheres gave overestimated values of refractive index perhaps due to restrictions of Mie theory on the minimum particle size.

The spectra of light reflection by plasmonic metal films deposited in vacuum on dielectric substrates and subsequently annealed at high temperatures are investigated. To explain the optical properties of plasmonic films, a theoretical model of a plane-layered metal-dielectric medium is used. One of the layers of such a structure has the dielectric constant of the metal under study, and the second layer has the dielectric constant calculated within the Maxwell-Garnett approximation for a heterogeneous medium consisting of a suspension of metallic nanoellipsoids in air. The introduction of this layer makes it possible to qualitatively take into account the inhomogeneities of the plasmon film surface. It is shown that the developed model allows a number of features in the experimental reflection spectra to be explained.

The article discusses the issues of inhibition of spontaneous emission of molecules by using silicon spherical nanoparticles and dimers made from them. It is shown that at different wavelengths of the visible spectral range, the value of the total spontaneous transitions rate in a molecule located at an optimal distance with respect to the structure with silicon nanospheres and at an optimal size of the structure can be up to 5–10 times lower than the transition rate in the case when the nanoparticles are absent.

Abstract—At present, plasmon effects in metal nanoparticles are used, among other purposes, for improvement in the efficiency of light-emitting diodes (LEDs). One new direction can be the application of plasmon properties of nanoparticles for improvement in the characteristics of wireless optical networks, in which data are transferred with the use of LEDs (Li–Fi networks). The study is concerned with issues related to the use of metal nanoparticles with dielectric shells to accelerate the modulation rate of LEDs and, as a consequence, to increase the data transfer rate in wireless optical networks due to an increase in the transition rates in a nanocrystal located near the nanoparticle surface. The dependences of the radiative and nonradiative transition rates in a nanocrystal on the emission wavelength are studied for different diameters of the metal core and different shell thicknesses. It is shown that, by specifying the optimal configuration of a nanoparticle with a shell, it is possible to create conditions such that the increase in the radiative transition rate at the emission wavelength of a nanocrystal will substantially exceed the increase in the nonradiative transition rate. This will allow acceleration of the modulation of LEDs without a loss in their energy efficiency as light sources. The results obtained here can be useful in studying the fluorescence of molecules and nanocrystals near nanoparticles and in improving the characteristics of Li–Fi optical data transfer networks.

We demonstrate theoretically the possibility to achieve domination of anti-Stokes Raman scattering enhancement over the Stokes one by means of photon local density of states (LDOS) engineering in model plasmonic nanostructures. The theory predicts anti-Stokes over Stokes scattering enhancement domination when both anti-Stokes and Stokes secondary photons energies correspond to the descending long-wave wing of extinction spectra of metal nanoparticles. The photon LDOS effect is proposed as a rationale for anti-Stokes anomalies reported for surface enhanced Raman spectroscopy, and the model of a dimer formed by two nanospheres is found to provide the reasonable agreement with experimental data explaining both promotion and inhibition of anti-Stokes scattering depending on the laser wavelength used. Our consideration means that evaluation of local temperature based on the anti-Stokes/Stokes ratio in Raman scattering for plasmonic structures cannot be performed. The simple models of isolated and coupled spheres and isolated spheroids, though offering strong anti-Stokes/Stokes enhancement asymmetry, do not promise absolute domination of anti-Stokes process versus the Stokes one, which is necessary for laser cooling effects. In a more general context, photon DOS engineering can be purposefully used to highlight anti-Stokes versus Stokes scattering even in the case of inhibited Raman scattering, provided that d(LDOS)/d omega >> 1 holds, that is, DOS sharply grows with frequency.

Nanoplasmonics represents one of the most extensive research fields in optics on the nanoscale and has emerging applications in sensors, light-emitting devices, and photovoltaic devices. It offers a number of effects and can be combined with existing technologies by a number of approaches, the colloidal techniques representing the easiest implementation in the existing and emerging photonic components and devices. In this article, plasmonic effects are discussed in terms of three major physical phenomena (incident field enhancement, photon density of states enhancement, and nonradiative decay enhancement) in the context of various photonic processes and devices related to Raman scattering, photo- and electroluminescence, photovoltaics, photochemistry, and photodetectors. A number of instructive examples are given for metal nanospheres and nanorods showing how size, shape, core-shell design, and ambient environment can be used to get maximal use of the favorable factors while keeping unfavorable ones at reasonably safe level. A number of aspects of plasmonically enhanced secondary radiation are emphasized which have not gained close consideration to date. Among them, the following properties are discussed: the decisive role of scattering component of metal-dielectric extinction spectrum overlapping with incident and emitted/scattered light wavelength, valuable contribution to enhancement factors from spacers used to prevent emission quenching but simultaneously affecting the extinction spectrum, a pronounced dependence of enhancement factors on dielectric permittivity of the substrate, dielectric shell, and ambient medium.

The article discusses the issues of modifying the photoluminescence intensity of quantum dipole emitters (molecules, quantum dots (nanocryslalls)) located near metal spherical nanoparticles with a dielectric shell. It is shown that by specifying the optimal configuration of a nanoparticle with a shell and the position of the emitter, it is possible to create the conditions, under which an increase in the photoluminescence intensity can be greater than in the case of the same nanoparticle without a shell.

In the context of using portions of a photosynthetic apparatus of green plants and photosynthesizing bacteria in bioinspired photovoltaic systems, we consider possible control of the chlorophyll excited state decay rate using nanoantennas in the form of a single metal and semiconductor nanoparticle. Since chlorophyll luminescence competes with electron delivery for chemical reactions chain and also to an external circuit, we examine possible excited state decay inhibition contrary to radiative rate enhancement. Both metal and semiconductor nanoparticles enable inhibition of radiative decay rate by one order of the magnitude as compared to that in vacuum, whereas a metal nanosphere cannot perform the overall decay inhibition since slowing down of radiative decay occurs only along with the similar growth of its nonradiative counterpart whereas a semiconductor nanoantenna is lossless. Additionally, at normal orientation of the emitter dipole moment to a nanoparticle surface, a silicon nanoparticle promotes enhancement of radiative decay by one order of the magnitude within the whole visible range. Our results can be used for other photochemical or photovoltaic processes, and strong radiative decay enhancement found for dielectric nanoantennas paves the way to radiative decays and light emitters engineering without non-radiative losses.

Plasmon-exciton coupling is of great importance to many optical devices and applications. One of the coupling manifestations is plasmon-enhanced fluorescence. Although this effect is demonstrated in numerous experimental and theoretical works, there are different particle shapes for which this effect is not fully investigated. In this work electrostatic complexes of gold nanorods and CdSe/CdZnS quantum dots were studied. Double-resonant gold nanorods have an advantage of the simultaneous enhancement of the absorption and emission when the plasmon bands match the excitation and fluorescence wavelengths of an emitter. A relationship between the concentration of quantum dots in the complexes and the enhancement factor was established. It was demonstrated that the enhancement factor is inversely proportional to the concentration of quantum dots. The maximal fluorescence enhancement by 10.8 times was observed in the complex with the smallest relative concentration of 2.5 quantum dots per rod and approximately 5 nm distance between them. Moreover, the influence of quantum dot location on the gold nanorod surface plays an important role. Theoretical study and experimental data indicate that only the position near the nanorod ends provides the enhancement. At the same time, the localization of quantum dots on the sides of the nanorods leads to the fluorescence quenching.