Strong resonant light scattering by individual spherical Si nanoparticles is experimentally demonstrated, revealing pronounced resonances associated with the excitation of magnetic and electric modes in these nanoparticles. It is shown that the low-frequency resonance corresponds to the magnetic dipole excitation. Due to high permittivity, the magnetic dipole resonance is observed in the visible spectral range for Si nanoparticles with diameters of ∼200 nm, thereby opening a way to the realization of isotropic optical metamaterials with strong magnetic responses in the visible region.

Silicon nanoparticles with sizes of a few hundred nanometres exhibit unique optical properties due to their strong electric and magnetic dipole responses in the visible range. Here we demonstrate a novel laser printing technique for the controlled fabrication and precise deposition of silicon nanoparticles. Using femtosecond laser pulses it is possible to vary the size of Si nanoparticles and their crystallographic phase. Si nanoparticles produced by femtosecond laser printing are initially in an amorphous phase (a-Si). They can be converted into the crystalline phase (c-Si) by irradiating them with a second femtosecond laser pulse. The resonance-scattering spectrum of c-Si nanoparticles, compared with that of a-Si nanoparticles, is blue shifted and its peak intensity is about three times higher. Resonant optical responses of dielectric nanoparticles are characterized by accumulation of electromagnetic energy in the excited modes, which can be used for the realization of nanoantennas, nanolasers and metamaterials.

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We report the optical response of dielectric sub-micrometer particle dimers with resonances in the visible, illustrating a hybridization of electric and magnetic dipolar modes of their individual constituents. The experimental results, corroborated by the numerical calculations, reveal the contributions to the scattering from homogeneous pairs of dipolar electric−electric and magnetic−magnetic modes, as well as from the heterogeneous electric−magnetic modes, induced due to the overlap between the electric and magnetic polarizabilities of single scatterers. The silicon nanoparticles are fabricated on glass by a laser printing method and characterized by polarization-resolved dark-field microscopy. Extensive numerical calculations are carried out to investigate the influence of the morphology and oxidation of the dimers on the optical response in order to properly model their hybridization.

Recent trends to employ high-index dielectric particles in nanophotonics are motivated by their reduced dissipative losses and large resonant enhancement of nonlinear effects at the nanoscale. Because silicon is a centrosymmetric material, the studies of nonlinear optical properties of silicon nanoparticles have been targeting primarily the third-harmonic generation effects. Here we demonstrate, both experimentally and theoretically, that resonantly excited nanocrystalline silicon nanoparticles fabricated by an optimized laser printing technique can exhibit strong second-harmonic generation (SHG) effects. We attribute an unexpectedly high yield of the nonlinear conversion to a nanocrystalline structure of nanoparticles supporting the Mie resonances. The demonstrated efficient SHG at green light from a single silicon nanoparticle is 2 orders of magnitude higher than that from unstructured silicon films. This efficiency is significantly higher than that of many plasmonic nanostructures and small silicon nanoparticles in the visible range, and it can be useful for a design of nonlinear nanoantennas and silicon-based integrated light sources.

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A recently introduced femtosecond laser printing technique was further developed for the fabrication of crystalline single Ge and SiGe nanoparticles (NPs). Amorphous Ge and SiGe thin films deposited by e-beam evaporation on a transparent substrate were used as donors. The developed approach is based on a laser-induced forward transfer process, which provides an opportunity for NP-controlled positioning on different types of receiver substrates. The size of the generated nanoparticles can be varied from about 100 to 300 nm depending on the laser pulse energy and wavelength. The crystallinity and composition of nanoparticles are both confirmed by the Raman spectroscopy measurements. The experimental visible scattering spectra of single nanoparticles are found to be well coincident with theoretical simulations performed on the basis of Mie theory. It is demonstrated that Ge and SiGe nanoparticles are characterized by electric and magnetic dipole resonances in the visible and near-infrared spectral ranges, which is promising for photonic applications.

In this paper, we present a plasmonic model system for the realization of ultrafast all-optical NOT, AND, OR, and XOR gate operations using linear interference effects in dielectric crossed waveguide structures. The waveguides for the surface plasmon-polaritons are produced by a simple but highly accurate microscopic lithographic process and are optimized for single mode operation at an excitation laser wavelength of 800 nm. The functionality of the presented structures is demonstrated using sub-30 fs laser pulses from a mode locked titanium:sapphire laser. Using leakage radiation microscopy we show ultrafast SPP switching and logic operations of one basic structure consisting of two crossed waveguides with an additional output waveguide along the bisecting line of the input waveguides. The individual gates are realized on a footprint of 10 µm × 20 µm. Experimental investigations are supported by finite-difference time-domain simulations, where good agreement between experimental results and numerical simulations is obtained. To exploit the high precision of the fabrication method and its huge potential for realizing functional complex plasmonic circuitry we experimentally demonstrate a half-adder structure and its operation by combining and cascading several plasmonic waveguide components and logic gate elements on an area of only 10 µm × 28 µm.