Alexander S. Shorokhov

Enhanced Third-Harmonic Generation in Silicon Nanoparticles Driven by Magnetic Response

We observe enhanced third-harmonic generation from silicon nanodisks exhibiting both electric and magnetic dipolar resonances. Experimental characterization of the nonlinear optical response through third-harmonic microscopy and spectroscopy reveals that the third-harmonic generation is significantly enhanced in the vicinity of the magnetic dipole resonances. The field localization at the magnetic resonance results in two orders of magnitude enhancement of the harmonic intensity with respect to unstructured bulk silicon with the conversion efficiency limited only by the two-photon absorption in the substrate.

Ultrafast All-Optical Switching with Magnetic Resonances in Nonlinear Dielectric Nanostructures

We demonstrate experimentally ultrafast all-optical switching in subwavelength nonlinear dielectric nanostructures exhibiting localized magnetic Mie resonances. We employ amorphous silicon nanodisks to achieve strong self-modulation of femtosecond pulses with a depth of 60% at picojoule-per-disk pump energies. In the pump-probe measurements, we reveal that switching in the nanodisks can be governed by pulse-limited 65 fs-long two-photon absorption being enhanced by a factor of 80 with respect to the unstructured silicon film. We also show that undesirable free-carrier effects can be suppressed by a proper spectral positioning of the magnetic resonance, making such a structure the fastest all-optical switch operating at the nanoscale.

Multifold Enhancement of Third-Harmonic Generation in Dielectric Nanoparticles Driven by Magnetic Fano Resonances

Strong Mie-type magnetic dipole resonances in all-dielectric nanostructures provide novel opportunities for enhancing nonlinear effects at the nanoscale due to the intense electric and magnetic fields trapped within the individual nanoparticles. Here we study third-harmonic generation from quadrumers of silicon nanodisks supporting high-quality collective modes associated with the magnetic Fano resonance. We observe nontrivial wavelength and angular dependencies of the generated harmonic signal featuring a multifold enhancement of the nonlinear response in oligomeric systems.

Ultrafast control of third-order optical nonlinearities in fishnet metamaterials.

Nonlinear photonic nanostructures that allow efficient all-optical switching are considered to be a prospective platform for novel building blocks in photonics. We performed time-resolved measurements of the photoinduced transient third-order nonlinear optical response of a fishnet metamaterial. The mutual influence of two non-collinear pulses exciting the magnetic resonance of the metamaterial was probed by detecting the third-harmonic radiation as a function of the time delay between pulses. Subpicosecond-scale dynamics of the metamaterial’s χ(3) was observed; the all-optical χ(3) modulation depth was found to be approximately 70% at a pump fluence of only 20 μJ/cm2.

Third-harmonic generation from Mie-type resonances of isolated all-dielectric nanoparticles

Subwavelength silicon nanoparticles are known to support strongly localized Mie-type modes, including those with resonant electric and magnetic dipolar polarizabilities. Here we compare experimentally the efficiency of the third-harmonic generation from isolated silicon nanodiscs for resonant excitation at the two types of dipolar resonances. Using nonlinear spectroscopy, we observe that the magnetic dipolar mode yields more efficient third-harmonic radiation in contrast to the electric dipolar (ED) mode. This is further supported by full-wave numerical simulations, where the volume-integrated local fields and the directly simulated nonlinear response are shown to be negligible at the ED resonance compared with the magnetic one. This article is part of the themed issue ‘New horizons for nanophotonics’.

Nonlinear Properties of "Magnetic Light"

Control of light at the nanoscale is demanding for future successful on-chip integration. At the subwavelength scale, the conventional optical elements such as lenses become not functional, and they require conceptually new approach for a design of nanoscale photonic devices. The most common approach to the subwavelength photonics is based on plasmonic nanoparticles and plasmonic waveguides due to their ability to capture and concentrate visible light at subwavelength dimensions. But the main drawback of all plasmonic devices is their intrinsic losses due to metallic components which affect strongly the overall performance of plasmonic structures limiting their scalability and practical use.

Enhanced magneto-optical effects in dielectric Mie-resonant metasurfaces

The concept of the rapidly developing area of high-index resonant meta-optics is extended to the field of mag- netically active materials. We numerically analyze magneto-optical response of hybrid nickel-silicon (Ni/Si) nanoantennas in comparison with an all-dielectric analog based on the bismuth substituted iron yttrium garnet- silicon (Bi:YIG/Si) nanoantennas. The results demonstrate the multifold enhancement of the magneto-optical effects due to the Mie-type resonances excitation in the structure. To further optimize the magneto-optical re- sponse and achieve a significant enhancement of the effect, the metasurfaces composed of Ni/Si nanoantennas of the different shape and configuration are numerically simulated. The magneto-optical effects can be significantly enhanced by means of the specific design of these hybrid metasurfaces.

Local field coupling effects in silicon oligomers revealed by third-harmonic generation microscopy

All-dielectric nanoparticles clusters have been attracted the attention recently due to their ability to sustain the specific collective modes excitation leading to new interesting effects such as Fano resonances. However, it is difficult to recognize such modes in the linear optical response of the structure without detecting the near field profile directly. In this work we propose a new method for detection of the oligomer eigenmodes excitation and numerically proof it for the nanoparticles cluster in the form of a trimer. These modes are indistinguishable in the linear optical response of the structure, but manifest themselves in the nonlinear response such as third- harmonic generation dependence on the pump polarization orientation. We belief that our method can be used for experimental identification of the eigenmodes of the complex all-dielectric structures such as oligomers of all-dielectric nanoparticles.

Ultrafast dynamics of light scattering in resonant GaAs nanoantennas

Active dielectric nanostructures have become one of the most popular trend lines in the modern dielectric nanophotonics due to great opportunities, which are offered by their numerous practical applications. Particularly, the concept of an optical switcher in nanophotonic circuitry can be realized by so-called all-optical mechanism, which could be carried out by a nanoantenna, such as an asymmetric dimer comprised of resonant nanoparticles made of material with high refractive index. In this case all-optical switching can be defined as the change of the trajectory of the femtosecond laser pulse after scattering on the nanoantenna, which was pumped by the other strong laser pulse. The realization of such effects would be a significant advance on the path to a novel technology. In this paper, we numerically demonstrate all-optical switching in the cylindrical asymmetric GaAs nanodimer, with the relaxation time of 10 ps and the deflection angle of the probe pulse of 7° for the relatively low intensities of the pumping .

Magneto-optical effects from nanoparticles enhanced by Mie resonances

Control of light by an external magnetic field is one of the important methods for modulation of its intensity and polarization. Magneto-optical effects at the nanoscale are usually observed in nanostructured hybrid materials or magnetoplasmonic crystals. In this work, we combine the advantages of all-dielectric resonant nanostructures and magnetic materials for creating compact active magneto-optical metadevices. High-index nanostructures offer novel opportunities for controlling light at the nanoscale based on a strong localization of both electric and magnetic fields in such structures near the corresponding Mie resonance [1]. This fact makes them similar to plasmonic nanostructures with clear advantage that all-dielectric meta-optics structures composed of nanoparticles with high refractive index can overcome this limit and initiate a new platform for nanophotonic metadevices [2]. As the important next step in this field, we consider a control of optical properties by an applied magnetic field, known to be an effective tool for many plasmonic structures [3, 4].