An extended family of perforated submicrometer hollow or core-shell plasmonic particles as antireflective synthetic brochosomes

We investigated different biomimetic structures inspired by natural brochosome powders which appear on the bodies and wings of leafhoppers (insects from the Cicadellidae family). All structures we analyzed are roughly spherical, with diameters 200 nm to 1000 nm, with a core and a shell made of different materials and the core perforated with subwavelength holes with diameters of the order of tens of nanometers. We extended the range of possible designs, geometries and materials of synthetic brochosomes, inspired by their natural counterparts found as powders secreted by various species of leafhoppers. We performed simulation of the optical properties of the structures using the finite element method. We found out that our approach ensures the design of highly efficient omnidirectional ultra-antireflective diffractive powders with subwavelength apertures. The reflectivity of 600 nm diameter holey spheres does not exceed 0.02% in 500-600 nm range. We showed that planar arrays of plasmonic-based artificial brochosomes exhibit a rich optical behavior, including effective refractive index below unity and even below zero at longer wavelengths. Such metamaterial-like behavior contributes to the multifunctionality of our synthetic brochosomes which can already serve as antireflective, superhydrophobic and highly porous structures controllable by design. This kind of versatility shows potentials for numerous practical uses. A major part of the novel functionalities stems from the use of nanocomposites containing free-electron conductors (plasmonic materials). Thus we arrived at a toolbox for the design of highly customizable antireflective layers. Potential fields of use include photodetectors, photoelectrochemistry, photocatalysis and general microoptoelectromechanical (MOEMS) systems.

Nano polarimetry: enhanced AFM-NSOM triple-mode polarimeter tip

A novel application of a combined and enhanced NSOM-AFM tip-photodetector system resulted in a nanoscale Polarimeter, generated by four different holes, each sharing a different shape, and enabling that the four photonic readouts forming the tip will be the four Stokes coefficients, this in order to place the polarization state in the Poincare sphere. The new system has been built on standard Atomic Force Microscope (AFM) cantilever, in order to serve as a triple-mode scanning system, sharing complementary scanning topography, optical data analysis and polarization states. This new device, which has been designed and simulated using Comsol Multi-Physics software package, consists in a Platinum-Silicon drilled conical photodetector, sharing subwavelength apertures, and has been processed using advanced nanotechnology tools on a commercial silicon cantilever. After a comparison study of drilled versus filled tips advantages, and of several optics phenomena such as interferences, the article presents the added value of multiple-apertures scanning tip for nano-polarimetry.

Плазмонное усиление поля в фотоприемниках среднего ИК-диапазона на базе квантовых точек Ge/Si с различной толщиной активной зоны

The spatial distribution of the electric field in Ge/Si photodetector heterostructures coated with a gold film containing a regular two-dimensional array of subwavelength apertures is calculated by the finite-element method. The array period and aperture diameter are 1.2 and 0.7 μm, respectively. The efficiency of field enhancement is determined for different thicknesses of the active region occupied by quantum dots. It is demonstrated that the field-enhancement factor for an electromagnetic wave incident on the structure from the side of the substrate is ~3.5 times larger than that for a wave incident from the opposite side. In the first case, the field-enhancement factor varies nonmonotonically with the thickness of the active region.