D. G. Baranov

All-dielectric nanoantennas for unidirectional excitation of electromagnetic guided modes

Engineering of intensity and direction of radiation from a single quantum emitter by means of structuring of their environment at the nanoscale is at the cornerstone of modern nanophotonics. Systems exhibiting spin–orbit coupling of light are of particular interest in this context. In this letter, we have demonstrated that the asymmetrical excitation of a high-index subwavelength ( λ/3−λ/2) dielectric nanoparticle by a point dipole source located in a notch at its surface results in formation of a chiral near field, which is similar to that of a circularly polarized dipole or quadrupole. Using numerical simulations, we have shown that this effect is the result of a higher multipole (quadrupole and octupole) modes excitation within the nanoparticle. We have applied this effect for unidirectional excitation of dielectric waveguide and surface plasmon-polariton modes. We have achieved the value of front–to–back ratio up to 5.5 for dielectric waveguide and to 7.5 for the plasmonic one. Our results are importa...

Magneto-optical spaser

We present an electrodynamical model of a quantum plasmonic device--the magneto-optical (MO) spaser. It is shown that a spherical gain nanoparticle coated with a metallic MO shell can operate as a spaser amplifying circularly polarized surface plasmons. The MO spaser may be used in design of an optical isolator in plasmonic transmission lines as well as in spaser spectrometry of chiral molecules.

Exactly solvable toy model for surface plasmon amplification by stimulated emission of radiation

We propose an exactly solvable electrodynamical model for surface plasmon amplification by stimulated emission of radiation (spaser). The gain medium is described in terms of the nonlinear permittivity with negative losses. The model demonstrates the main feature of a spaser: a self-oscillating state (spasing) arising without an external driving field if the pumping exceeds some threshold value. In addition, it properly describes synchronization of a spaser by an external field within the Arnold tongue and the possibility of compensating for Joule losses when the pumping is below threshold. The model also gives correct qualitative dependencies of spaser characteristics on pumping.

Loss compensation by spasers in plasmonic systems

We show that in plasmonic systems, exact loss compensation can be achieved with the help of spasers pumped over a wide range of pumping values both below and above the spasing threshold. We demonstrate that the difference between spaser operation below and above the spasing threshold vanishes, when the spaser is synchronized by an external field. As the spasing threshold loses its significance, a new pumping threshold, the threshold of loss compensation, arises. Below this threshold, which is smaller than the spasing threshold, compensation is impossible at any frequency of the external field.

Magneto-optics enhancement with gain-assisted plasmonic subdiffraction chains

We study enhancement of the magneto-optical (MO) effect in subdiffraction plasmonic chains. We show that, in a periodic chain of the plasmonic nanoparticles embedded in an MO medium, propagation of a guided mode is accompanied by rotation of electric dipoles (the Faraday effect). The angle of rotation per unit length is an order of magnitude greater than that in the same bulk MO medium. We also demonstrate that the effect of Joule losses can be significantly reduced by using a gain-assisted chain composed of active core-shell nanoparticles (spasers). The guided mode in such an array of MO spasers exhibits high values of the Faraday rotation and propagation length.We study the enhancement of the magneto-optical effect in subdiffraction plasmonic chains. We show that in a periodic chain of the plasmonic nanoparticles embedded in a magneto-optical medium, propagation of a guided mode is accompanied by rotation of electrical dipoles (the Faraday effect). The angle of rotation per 1 {mu}m is two orders of magnitude greater than that in the same bulk magneto-optical medium. We also demonstrate that the effect of Ohmic losses can be significantly reduced by using a gain-assisted chain composed of active core-shell nanoparticles (spasers). The dipole mode in such an array of magneto-optical spasers exhibits high values of the Faraday rotation and propagation length.

Abrupt Rabi oscillations in a superoscillating electric field

We study counterintuitive dynamics of a two-level system (TLS) interacting with electric field superoscillating in time. We show that a TLS may be excited by an external light pulse whose spectral components are below the absorption line of the TLS. We attribute this unique dynamics to the Rabi oscillations of the TLS in a superoscillating driving field.We study counterintuitive dynamics of a two-level system (TLS) interacting with electric field superoscillating in time. We show that a TLS may be excited by an external light pulse whose spectral components are below the absorption line of the TLS. We attribute this unique dynamics to the Rabi oscillations of the TLS in a superoscillating driving field.

Superoscillating response of a nonlinear system on a harmonic signal

We demonstrate that a superoscillating in time signal may be obtained as a nonlinear response to a single low-frequency harmonic input. Using the realization of a superoscillating function proposed by Huang et al. (J Opt A Pure Appl Opt 9:S285, 2007), which is a mixture of five different harmonics, as an example, we synthesize the response function of such a nonlinear transformer and investigate its robustness with respect to the frequency and amplitude variations of the input signal.

Resonant optical properties of crystalline silicon nanoparticles fabricated by laser ablation-based methods

In this work we demonstrate resonant Raman scattering from crystalline silicon nanoparticles, fabriacted using a single-stage fabrication process based on femtosecond laser ablation. Experimental and analtyical modelling shows 140-times enhancement of Raman scattering from Resonant nanoparticles, relative to their nonresonant counterparts.In this work we demonstrate resonant Raman scattering from crystalline silicon nanoparticles, fabriacted using a single-stage fabrication process based on femtosecond laser ablation. Experimental and analtyical modelling shows 140-times enhancement of Raman scattering from Resonant nanoparticles, relative to their nonresonant counterparts.

Ultrafast magnetic light

We present our recent results on efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photo-injection of dense (> 1020 cm-3) electron-hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows to manipulate by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20% tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such single-particle nanodevice enables to design fast and ultracompact optical switchers and modulators.

Reversible and non-reversible tuning of hybrid optical nanoresonators

Recently, we have proposed a novel approach for fabrication of asymmetric metal-dielectric (hybrid) nanoparticles via combination of standard lithography processes and femtosecond laser reshaping of a metal component of the nanoparticle. Here, we study the influence of the geometrical parameters of the hybrid nanoparticle on the reshaping process. We also demonstrate non-reversible tuning of light absorbtion and reversible tuning of transmittance of the hybrid nanostructures in a wide range.