ИСТИНА

Fano resonances arising from the interference of modes with wide and narrow spectra have relevant applications in physical, chemical, and biological systems (see [1] Luk`yanchuk B., Zheludev N.I, Maier S.A, Halas N.J, Nordlander P., Giessen H ., Chong T.C “The Fano resonance in plasmonic nanostructures and metamaterials”, Nature Materials 9, 707-715 (2010)). The Fano resonance amplitude increases for a higher-order mode, for example, the interference of a wide dipole (Rayleigh) mode and a narrow octupole mode provides a stronger resonance than a similar interference of a dipole and quadrupole modes in a plasmon particle (see, for example, Fig. 3 in [1 ]). Excitation of high-order resonances by Fano makes it possible to increase the sensitivity of resonant nanostructures. Fano resonances of the first four orders (quadrupole, octupole, hexadecapole and triacontadipole) were generated in an optimized plasmon silver ring nanostructure (see [2] Fu Y.H, Zhang J.B, Yu Y.F, Luk`yanchuk B. “Generating and Manipulating Higher Order Fano Resonances in Dual-Disk Ring Plasmonic Nanostructures ”, ACS Nano 6, 5130-5137 (2012)). However, the advancement to Fano of higher-order resonances in plasmonics is difficult due to the visible effects of dissipation in metal structures. On the contrary, in dielectric materials, the dissipation effect can be weak, which makes it possible to realize high-order Fano resonances, for example, with resonant multipoles of the order of n = 30. Weakly absorbing dielectric spheres with a relatively low refractive index (glass, quartz, etc.) make it possible to realize high-order Fano resonances for internal Mie modes in the optical spectral region. These resonances for specific values ​​of the size parameter (the ratio of the particle size to the wavelength of laser radiation) give field strength amplification factors of the order of 10 ^ 4–10 ^ 7, which follow from analytical calculations. Such "superresonances" provide magnetic nanostructured generators with giant magnetic fields, which is attractive for many applications. In the case of materials with large values ​​of the refractive index (silicon, germanium, etc.), it is also possible to realize high-order Fano resonances in the IR spectral region. An important feature of the project is the implementation of internal Fano resonances directly in the electric and magnetic intensities. Unlike the Fano resonance in the scattering efficiency (of the order of 20%), the Fano resonance inside a dielectric particle with a size of the order of 10 micrometers increases the fields hundreds and thousands of times (see [3] Wang Z.B, Luk`yanchuk B. et al. “Super-resonances in microspheres: extreme effects in field localization”, arXiv: 1906.09636 (2019)). Especially strong effects are observed for magnetic fields. This is due only to the intensities of the bias currents, but also to the small size of the excited optical vortices (according to the Biot-Savart law, the magnetic field in the center of the coil with the current is proportional to the ratio of the current to the radius of the coil). The possibility of exciting optical nanovortices was previously discussed for both plasmonic and dielectric structures ([4] Luk`yanchuk B. et al, “Fano resonances and topological optics: an interplay of far- and near-field interference phenomena”, Journal of Optics 15, 073001 (2013); [5] A.I Kuznetsov, A.E Miroshnichenko, M.L Brongersma, Y.S Kivshar, B. Luk'yanchuk, “Optically resonant dielectric nanostructures”, Science 354, aag2472 (2016)). In the case of high-order Fano resonances, the vortex sizes can be very small near singularities, which is due to the effect of superoscillations (see [6] M. Berry, N. Zheludev et al, “Roadmap on superoscillations”, J. Opt. 21, 053002 ( 2019)). Excitation of high-order Fano resonances in transparent dielectric materials provides a unique opportunity for creating strong magnetic fields inside and near the surface of a microscopic particle. This phenomenon can be observed in the visible region of the spectrum using simple glass microspheres. Such microspheres make it possible to increase the magnetic field of light (which is usually small) by several orders of magnitude. We believe that these superresonances are an attractive platform for a number of promising applications, such as, for example, the enhanced absorption effect, ablation caused by magnetic pressure, magnetic nonlinear optical effects, etc. High-order Fano resonances are accompanied by the formation of regions with high values ​​of the local wave vector. This allows one to overcome the diffraction limit, for example, in a scheme with the formation of an imaginary optical image using a transparent optical particle with a size of the order of ten micrometers (see [7] Wang Z.B, Luk'yanchuk B., 'Super-resolution imaging and microscopy by dielectric particle -lenses ”, Chapter 15 in 'Label-Free Super-resolution Microscopy', pp. 371-400 (Springer, 2019). We will also develop a direction related to particles with a high refractive index for the design of dielectric nanoantennas, metasurfaces, and other resonant meta devices. This direction continues our previous studies on the mega-grant “Nonlinear and Extreme Nanophotonics” (Ministry of Education and Science of the Russian Federation # 14.W03.31.0008, 2017-2019), (see, for example, [8] R. Paniagua-Domingues, B. Luk'yanchuk, A.I. Kuznetsov, “Control of scattering by isolated dielectric nanoantennas”, Chapter 3 in “Dielectric Metamaterials: Fundamentals Designs and Applications” (Elsevier, Nederland's 2019), [9] R. Paniagua-Domínguez, B. Luk 'yanchuk, A. Miroshnichenko, JA Sánchez-Gil, "Dielectric Nanoresonators and Metamaterials", Journal of Applied Physics 126, 150401 (2019)) In studies related to high-order Fano resonances, of particular interest are magnetic nonlinearities due to the dependence of magnetic permeability on the magnitude of the magnetic field, as well as combined magnetoelectric processes, where both types of nonlinearities are dielectric (as a function of electric field) and magnetic (as a function of magnetic permeability fields play an essential role in changing the refractive index. In the first case, it is necessary to provide a high contrast of the magnitude of the ratio of magnetic and electric intensities at a level exceeding 10^4. In combined processes, the contrast can be an order of magnitude lower. Also of interest is a further study of the effects of magnetic holography, begun in our work with the Singapore National University (see [10] Hao C., Nie Z., Ye H., Li H., Yu X., Zhang Y., Yu C. , Lei D., Luk'yanchuk B., Qiu CW, “Three-dimensional supercritical resolved light-induced magnetic holography”, Science Advances, vol. 3, issue 10, e1701398 (2017)). Naturally, analytical studies will be supplemented by experimental work related to the “proof of principles” and attractive potential applications, using laboratory equipment used to carry out work on megagrant # 14.W03.31.0008. We also intend to use our cooperation with the Institute of General Physics. A. M. Prokhorov RAS to perform studies with a transmission laser projection microscope based on the active medium of a copper vapor laser (see [11] Zemskov, KI, Kazaryan, MA, Savranskiĭ, VV, & Shafeev, GA (1979). light laser projection microscope. Soviet Journal of Quantum Electronics, 9 (11), 1464). Such a scheme was used to visualize changes in the structure of neurons of the grape cochlea during the generation of electrical impulses by them (see [12] E.A. Morozova, A. M. Prokhorov, V. V. Savransky, G. A. Shafeev, High-speed frame-by-frame image recording biological objects using a laser projection microscope, Reports of the Academy of Sciences of the USSR, T. 261. No. 6. P. 1460 (1981)). The effect of gain saturation in the active medium of a copper vapor laser on the gain of a light signal in a laser projection microscope was reported in F.V. [13] Bunkin, K.I. Zemskov, M.A. Kazaryan, V.M. Matveev, G.G. Petrash, V.V. Savranskiĭ, G.A. Shafeev, G. A., Power self-regulation and formation of a negative image in an illuminating beam of a laser projection microscope. Soviet Journal of Quantum Electronics, 11 (6), 829 (1981). The scheme of a laser projection microscope based on a copper vapor laser for local ablation of silicon under a liquid layer was applied in [14] G.A. Shafeev, A.V. Simakin, Spatially confined laser-induced damage of Si under a liquid layer, Appl. Phys. A 54, 311 (1992). In this regard, the project is relevant and of interest to the giants of the high-tech industry, as allows us to propose an improvement in existing technologies for processing optical signals and increasing the resolution of the microscope.