Complex conductivity of the topological insulator (TI) Bi2 − xSbxTe3 − ySey samples of various thicknesses and chemical compositions is studied by terahertz time-domain spectroscopy method in the range 0.5 to 2.5 THz. For the first time, a decrease in conductivity in the terahertz range has been observed as the chemical composition approaches the Ren’s curve. The generalized approximate expressions are obtained for complex conductivity with account of the lowest Eu1-phonon mode. Calculations of the Fermi energy and concentration of bulk carriers are performed. Based on the experimental data, an estimate of conductance of the topological states is obtained. The results can be useful in developing terahertz devices based on the specific surface transport in TIs.
We develop a new approach for creating photonic metasurfaces based on nematic liquid crystal material. The periodical modulation of the LC director field is imposed by nanoscale change of the alignment properties of polyimide thin layer by means of focused ion beam treatment. The resulted spatially periodic modulation with a period determined by that of the pattern at the substrate provides distinct photonic properties of LC layer. A part of transmitted light is redistributed into a few first diffraction orders. The diffraction is switchable by electric field with millisecond switching times.
In this paper we report on fabrication of a nanocomposite based on CdSe quantum dots mixed with commercial photoresist ORMOCOMP and proved its high structurability by direct laser writing. The distribution of quantum dots was visualised by transmission electron microscopy and the quality and geometrical parameters of the structures were studied by optical and atomic force microscopy. We manufactured a novel photonic device for Bloch surface electromagnetic waves in photonic crystals and thoroughly studied their propagation by both leakage microscopy and back focal plane imaging methods. By z-scan method we measured the nonlinear Kerr coefficient of quantum dots. Its high value makes the manufactured photonic device promising for all-optical switching applications.
The results of experimental observation of magneto-optical Kerr effect (MOKE) enhancement caused by surface
plasmon-polaritons (SPP) excitation in 1D and 2D magnetoplasmonic crystals are presented. One-dimensional
nickel magnetoplasmonic crystals have periodic structure formed by periodic nickel grooves made on nickel
surface. The period of the structure is 320 nm and the depth of the grooves is 50 nm. The second group of the
samples represents itself a 2D self-assembled hexagonally ordered monolayer of polystyrene (PS) microspheres
with diameters from 500 to 760 nm and covered by 100- nm - thick nickel film. MOKE measurements performed
in transversal configuration demonstrate that SPP excitation lead to transversal Kerr effect (TKE) enhancement
resulting as a sharp peak in TKE spectrum.
Experimental and calculated results of the investigation of electromagnetic field distribution including its polarization characteristics in the vicinity of the nanostructures are presented. Experimental investigation was realized by aperture type scanning near field optical microscopes (SNOM) which operated in collection mode and provided both high spatial resolution and large scanning range. Shear force detection was used for the control of aperture to surface gap. Normal resolution which allows resolving 0.3 nm height surface steps was demonstrated for this gap control system. Theoretical computation of electromagnetic field distribution was realized by finite-difference time-domain (FDTD) method. Experimental three-dimensional maps of intensity and polarization distribution as result of light diffraction at nanoaperture in metal screen, dielectric and metallized nanocylinders were obtained. The qualitative difference between the orthogonal polarized component distributions near nanoaperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. Spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized nanocylinders, which is unexpected from both experimental and theoretical points of view.
Experimental and calculated results of the investigation of electromagnetic field distribution including its polarization characteristics in the vicinity of the structures with subwavelength sizes are presented. The experimental investigation was realized by aperture type scanning near field optical microscope, which operated in collection mode and provided both high spatial resolution and large scanning range. Shear force detection was used for the control of aperture to surface gap. Normal resolution, which allows us to image down to 0.3 nm height surface steps, was demonstrated for this gap control system. Theoretical computation of electromagnetic field distribution was realized by finite-difference time-domain (FDTD) method. Experimental three-dimensional maps of intensity and polarization distribution as a result of light diffraction at subwavelength aperture in metal screen, dielectric and metallized subwavelength cylinders were obtained. The qualitative difference between the orthogonal polarized component distributions near subwavelength aperture in aluminium screen was experimentally shown. The electromagnetic field concentration in the proximity of the dielectric nanocylinders was observed. This observation gives good fit with the results of FDTD computations. A spiral type electromagnetic field distribution pattern was experimentally observed in the proximity of metallized subwavelength cylinders, which is unexpected from both experimental and theoretical points of view.
Quantum neural technology is a hypothetical but promising new field of informatics, which combines together the main ideas of both quantum and neural computing. There is a hope that this combination can resolve many problems of already existing classical neural technology, and also can give new opportunities to future quantum computing. Comparing with classical neural technology its quantum analog can enhance dramatically the capacity of neural modesl of associative memory, to facilitate the creation of neural hardware by eliminating the wiring problem, etc. On the other hand, as it will be argued in presented paper, quantum neural system can be used for realization of controllable quantum gates, which can be used in quantum computers, and in particular, in so-called type-II quantum computers.
The role of interference and entanglement in quantum neural processing is discussed. It is argued that on contrast to the quantum computing the problem of the use of exponential resources as the payment for the absence of entanglement does not exist for quantum neural processing. This is because of corresponding systems, as any modern classical artificial neural system, do not realize functions precisely, but approximate them by training on small sets of examples. It can permit to implement quantum neural systems optically, because in this case there is no need in exponential resources of optical devices (beam-splitters etc.). On the other hand, the role of entanglement in quantum neural processing is still very important, because it actually associates qubit states: this is necessary feature of quantum neural memory models.
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