All-Dielectric Optical Nanoantennas

We propose a new type of highly efficient Yagi-Uda nanoantenna and introduced a novel concept of superdirective nanoantennas based on silicon nanoparticles. In addition to the electric response, this silicon nanoantennas exhibit very strong magnetic resonances at the nanoscale. Both types of nanoantennas are studied analytically, numerically and experimentally. For superdirective nanoantennas we also predict the effect of the beam steering at the nanoscale characterized by a subwavelength sensitivity of the beam radiation direction to the source position

Hybrid anapole modes of high-index dielectric nanoparticles

We investigate the peculiarities of light scattering from subwavelength particles made of high-refractive-index materials caused by the coexistence of particular anapole modes of both electric and magnetic character. The similarities and differences of such anapole modes are discussed in detail. We also show that these two types of anapole modes can be supported simultaneously by subwavelength high-index spherical dielectric particles

Fano Resonances: A Discovery that Was Not Made 100 Years Ago

Scattering: We have missed the presence of resonant scattering behavior in the Rayleigh region for years, but a clue was lurking in quantum theory

Visualization 1: Refractive index less than two: photonic nanojets yesterday, today and tomorrow [Invited]

Supplementary Video showing nanojet formation in spheres Originally published in Optical Materials Express on 01 June 2017 (ome-7-6-1820

Dielectric meta-holograms enabled with dual magnetic resonances in visible light

Efficient transmission-type meta-holograms have been demonstrated using high-index dielectric nanostructures based on Huygens’ principle. It is crucial that the geometry size of building blocks be judiciously optimized individually for spectral overlap of electric and magnetic dipoles. In contrast, reflection-type meta-holograms using the metal/insulator/metal scheme and geometric phase can be readily achieved with high efficiency and small thickness. Here, we demonstrate a general platform for design of dual magnetic resonance based meta-holograms based on the geometric phase using silicon nanostructures that are quarter wavelength thick for visible light. Significantly, the projected holographic image can be unambiguously observed without a receiving screen even under the illumination of natural light. Within the well-developed semiconductor industry, our ultrathin magnetic resonance-based meta-holograms may have promising applications in anticounterfeiting and information security.1126sciescopu

Dielectric Meta-Holograms Enabled with Dual Magnetic Resonances in Visible Light

Efficient transmission-type meta-holograms have been demonstrated using high-index dielectric nanostructures based on Huygens’ principle. It is crucial that the geometry size of building blocks be judiciously optimized individually for spectral overlap of electric and magnetic dipoles. In contrast, reflection-type meta-holograms using the metal/insulator/metal scheme and geometric phase can be readily achieved with high efficiency and small thickness. Here, we demonstrate a general platform for design of dual magnetic resonance based meta-holograms based on the geometric phase using silicon nanostructures that are quarter wavelength thick for visible light. Significantly, the projected holographic image can be unambiguously observed without a receiving screen even under the illumination of natural light. Within the well-developed semiconductor industry, our ultrathin magnetic resonance-based meta-holograms may have promising applications in anticounterfeiting and information security

Subgroup decomposition of plasmonic resonances in hybrid oligomers: Modeling the resonance lineshape

10.1021/nl3003683Nano Letters1242101-2106NALE

Yellowing effect and discoloration of pigments: experimental and theoretical studies

Summarization: Two issues of great interest in the field of lasers in artwork conservation are the so-called yellowing effect and the discoloration of pigments. We have viewed these issues from a comprehensive point of view, considering all our present experimental results as well as ongoing modeling and theoretical calculations. The first concern to be discussed is the yellowing effect in laser cleaning of marble or stone artifacts. Although, in most cases, a yellowish layer exists underneath the black encrustation, the so-called ‘patina’, it has become clear that there are situations where yellowing cannot be attributed to an existing layer. In the present study, a light scattering model that may account for the yellowing is presented. This model considers a thin absorbent layer and the surface roughness and/or created voids and accounts for the reflectance spectra measured by (i) hyper-spectral imaging and (ii) integrating sphere. Additional experimental data, such as the absence of yellowing when the third harmonic of a Q-swihed Nd:YAG laser is used, support this model. A thorough understanding of the quantitative characteristics of pigment discoloration, on the other hand, has been attempted by means of X-ray diffraction and theoretical studies. The model developed suggests a nucleation process for cinnabar resulting in a structural modification within the volume of a pigment’s crystal or particle close to the ‘ablation front’, which extends for a few nanometers from its surface.Παρουσιάστηκε στο: Journal of Cultural Heritag