Optical properties of two-dimensional periodic systems of the dielectric micro bars and micro cones are investigated. Computer simulations as well as real experiment reveal anomalous optical response of the dielectric metasurface due to excitation of the dielectric and metal-dielectric resonances, which are excited in-between metal nanoparticles and dielectric cones and bars. In the metal-dielectric resonance local electric field can be orders on magnitude larger than the field in the plasmon resonance only. To investigate local electric field the signal molecules were deposited on the metal nanoparticles. We demonstrate the enhancement of the electro- magnetic field by detecting the Raman signal from the of organic acid molecules deposited on the investigated metasurface.
Photodynamic therapy becomes a widely spread method due to cancer growth in the world. However, to detect tumors at early stages, it is necessary to carry out diagnostic measures in a timely manner. Our aim was to test the developed pharmaceutical composition, which can be used for external application in early fluorescent diagnostics even in the absence of visual changes, as well as for therapy effectiveness control. Pharmacokinetic studies on laboratory animals and volunteers were carried out. The results have shown that the dipotassium salt of Yb3+-dimethoxyhematoporphyrin IX, which is highly soluble in water and stable in storage, is a promising marker for earlier diagnostics of tumors and can be used in dermatology, dentistry, gynecology, cosmetology, ear, nose, and throat diseases, veterinary, and in other areas of medicine.
New dielectric metamaterial based on the Bragg filter comprising ten dielectric bilayers was investigated. Each bilayer is the thin films of silicone dioxide (SiO2) and another film of zirconium dioxide (ZrO2). The surface of the multilayer film is profiled. It has a form of periodic system of rectangles separated by the open gaps. We use the computer simulation as well as analytical solution to find the reflectance of the multilayer as a function of the wavelength and electromagnetic (em) field distribution. The multilayer system reveals the enhancement of em fields at the surface. The considered Bragg filter was modified by Raman-active structure made of gold nanoparticles with chemically attached 3,3-thio-bis(6- nitrobenzoic acid) - (TNB). The high Surface Enhanced Raman Scattering (SERS) signal was detected.
The surface plasmon (SP) excitations in the periodical array of the nanorods have attracted a lot of attention in the recent
years due to the numerous potential applications in nanoplasmonics including transmitting and processing optical signals
on a scale much smaller than the wavelength. In our work the plasmonic and dielectric systems consisting of twodimensional
periodic arrays of nanorods are considered. We use computer simulation as well as exact analytical solution
to find reflectance and transmittance the plane array of the nanorods, which have various diameters and inter-particle
spacing. As the metal nanorods approach each other, series of surface plasmon resonances are excited. The resonances
are strongly localized between nanorods due to its collective nature. It is shown that the local electric field is much
enhanced in the interparticle gap and it concentrates at a scale much smaller than the diameter of the rod. The reflectance
and transmittance have sharp minima and maxima corresponding to the excitation of various SP resonances. The
computer simulations are in an agreement with our analytical theory. In the case of the dielectric nanorods the
phenomenon of the whispering gallery modes effect is considered. The resonance frequencies and field enhancement can
be tuned by variation of the shape and arrangement of the nanorods. The system of nanorods that almost touched each
other by their generatrices can be used to develop plasmon and dielectric substrates, which are the basic elements of high
sensitive SERS bio and chemical sensors.
For inhomogeneous mediums the optical Magnus effect has been derived. The metamaterials fabricated from amorphous ferromagnet Co-Fe-Cr-B-Si microwires are shown to exhibit a negative refractive index for electromagnetic waves over wide scale of GHz frequencies. Optical properties and optical Magnus effect of such metamaterials are tunable by an external magnetic field. Microwave permeability of glass-coated ferromagnetic amorphous microwire exhibiting a weak negative magnetostriction has been studied. The diameter of the microwire was about 20 μm and the diameter of the metal core was about 12 μm. The microwire was wound to comprise a 7/3 washer-shaped composite sample with the volume fraction of magnetic constituent of about 10%. The permeability of the composite sample was measured in a coaxial line in the frequency range from 0.1 to 10 GHz. The composite was found to exhibit a negative permeability within the frequency range from approximately 0.7 to 1.5 GHz, with the permeability being as low as -0.4. Therefore, microwire-based composites, particularly, crossed arrays of microwires may be employed to develop metamaterials for microwave applications. In the composite, the negative microwave permeability is due to the natural ferromagnetic resonance and the negative microwave permittivity is due to the inherent inductance of the wire. Such metamaterials are advantageous in simple design, isotropic in-plane performance, and possible tunability of performance by external magnetic bias. However, for a feasible metamaterial fabricated from microwire arrays, the wires have to exhibit higher magnitude of the ferromagnetic resonance, higher quality factor, and higher resonance frequency.