Fényemisszió plazmonikus erősítése

Light emission from nanoscopic sources is used in many fields of fundamental and applied research, such as nanophotonics, quantum information technology and medical diagnostics. Diamond color centers are photostable single-photon sources with optically tailorable and readable spin of long coherence time at room temperature. Nitrogen (NV) and silicon (SiV) vacancy are widely studied representatives of color centers. For effective quantum information applications, their luminosity and polarization contrast need to be increased and their lifetime need to be reduced. The emission properties of single-photon sources are affected by their environment. Localized surface plasmons are electron plasma oscillations, which can be resonantly excited on a nanoparticles smaller than or comparable to the operation wavelength. The nanophotonic environment can be modified by placing a properly designed individual plasmonic nanoresonator near the emitter. The resonance frequency and impact including the intense near-field enhancement, lifetime reduction via Purcell phenomenon and quantum efficiency increase by radiative decay fraction modification depend on the size, shape, and material properties of the nanoresonator. In the PhD thesis, I have modified and improved the numerical environment based on a finite element method to determine the optical response, namely the enhancement of excitation and spontaneous (non-cooperative) emission of a NV or SiV color center coupled to an arbitrary individual nanoresonator. Integrated with a robust optimization algorithm, GLOBAL, the method is suitable for maximizing the fluorescence enhancement of color centers through geometry tuning under desired conditions, by simultaneously improving the excitation and emission processes in demand. The in-house developed numerical method has been applied to optimize the geometry and configuration of nanorod and core-shell monomer or dimer coupled color center systems and to maximize their fluorescence. The optical response of the optimized systems has been a subject of a detailed analysis by determining the Purcell factor, quantum efficiency, radiative enhancement spectra, as well as the charge, near-field and far-field distributions to identify and analyze the properties of the contributing plasmonic modes

Active Individual Nanoresonators Optimized for Lasing and Spasing Operation

Plasmonic nanoresonators consisting of a gold nanorod and a spherical silica core and gold shell, both coated with a gain layer, were optimized to maximize the stimulated emission in the near‐field (NF‐c‐type) and the outcoupling into the far‐field (FF‐c‐type) and to enter into the spasing operation region (NF‐c*‐type). It was shown that in the case of a moderate dye concentra-tion, the nanorod has more advantages: smaller lasing threshold and larger slope efficiency and larger achieved intensities in the near‐field in addition to FF‐c‐type systems’ smaller gain and out-flow threshold, earlier dip‐to‐peak switching in the spectrum and slightly larger far‐field outcou-pling efficiency. However, the near‐field (far‐field) bandwidth is smaller for NF‐c‐type (FF‐c‐type) core–shell nanoresonators. In the case of a larger dye concentration (NF‐c*‐type), although the slope efficiency and near‐field intensity remain larger for the nanorod, the core–shell nanoresonator is more advantageous, considering the smaller lasing, outflow, absorption and extinction cross‐section thresholds and near‐field bandwidth as well as the significantly larger internal and external quantum efficiencies. It was also shown that the strong‐coupling of time‐competing plasmonic modes accompanies the transition from lasing to spasing occurring, when the extinction cross‐section crosses zero. As a result of the most efficient enhancement in the forward direction, the most uni-form far‐field distribution was achieved. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Szimmetria és Csoporthatások az Algebrai Topológiában = Symmetry and Group Actions in Algebraic Topology

Pályázatunk három, lazán összefüggő problémakört érint. Több kiemelkedő eredményt értünk el a Thom polinomok, és általánosabban, az ekvivariáns obstrukciók elméletében. A Thom sorok bevezetése és a Morin szingularitások Thom polinomjainak kiszámítása a terület legfontosabb eredményei az utóbbi években. A geometriai oldalon, komoly előrehaladást értünk el a hiperkahler modulusterek geometriájának leírásában, és sikerült bebizonyítanunk a Batyrev-Materov tükör reziduum sejtést tórikus orbifoldokra. Végezetül, projektünk algebrai eredményei között megemlítjük új 2-karakterisztikai jelenségek felfedezését az ortogonális csoport reprezentációelméletében, és a Zamolodcsikov periodicitási sejtés bizonyítását Y-rendszerekre. Ezenkívül, új algebrai egyenlőtlenségeket találtunk szemidefinit mátrixokra, és ezeket felhasználva megjavítottuk a legjobb ismert alsó becslést valós lineáris funkcionálok szorzatára. | The project deals with three loosely interconnected areas of mathematics. We obtained a number of outstanding results in the theory of Thom polynomials, and more generally, in equivariant obstruction theory. In particular, the introduction of Thom series, and the calculation of the Thom polynomials of Morin singularities are the most important advances in the subject in the last few years. On the more geometric side, we made serious progress in the description of the geometry of hyperkahler moduli spaces, and proved the Batyrev-Materov mirror residue conjecture for toric orbifolds. Finally, the more algebraic results of our project include discovering new characteristic-2 phenomena in the representation theory of the orthogonal group, and proving the Zamolodchikov periodicity conjecture for Y-systems. We also found new algebraic inequalities for semidefinite matrices, and using these, improved the best known lower bound on products of real linear functionals

Plasmonic nanoresonator distributions for uniform energy deposition in active targets

Active targets implanted with core-shell-composition (CS) and nanorod-shaped (NR) plasmonic nanoresonators and doped with dyes were designed to ensure uniform energy deposition during illumination by two-counter propagating short laser pulses. The near-field enhancement, optical responses, and cross-sections were mapped above the concentration-Epump parameter-plane to inspect two different regions (I and II) with the potential to improve light-matter interaction phenomena. The distribution of steady-state absorption, as well as of the power-loss and power-loss density integrated until the complete overlap of the two short pulses was determined. The uniform distribution was adjusted to constrain standard deviations of the integrated power-loss distributions in the order of ∼10%. Dye doping of target-I/II implanted with uniform CS (NR) nanoresonator distributions results in larger absorption with increased standard deviation, larger power-loss, and power-loss density with decreased (decreased / increased) standard deviation. The adjustment allows larger absorption in CS-II and larger power-loss and power-loss density in CS-implanted targets, smaller standard deviation in targets-I for absorption, and in all targets for power-loss and its density. Larger dye concentration makes it possible to achieve larger absorption (except in adjusted NR-II), larger power-loss and power-loss density in all CS and in adjusted NR distributions, with decreased standard deviation in CS-implanted targets for all quantities and in NR-implanted targets for absorption. CS implantation results in larger absorption with a larger standard deviation, moreover allows larger power-loss in adjusted distributions and smaller standard deviation in power-loss quantities for larger concentration in both distributions and the same standard deviation for smaller concentration in adjusted distribution. Based on these results, adjusted CS distributions in targets doped with a dye of higher concentration are proposed.publishedVersio

Superradiant diamond color center arrays coupled to concave plasmonic nanoresonators

Superradiantly enhanced emission of SiV diamond color centers was achieved via numerically optimized concave plasmonic nanoresonators. Advantages of different numbers of SiV color centers, diamond-silver (bare) and diamond-silver-diamond (coated) core-shell nanoresonator types, spherical and ellipsoidal geometries were compared. Indistinguishable superradiance is reached via four color centers, which is accompanied by line-width narrowing except in a coated ellipsoidal nanoresonator that outperforms its bare counterpart in superradiance. Seeding of both spherical and bare ellipsoidal nano-resonators with six color centers results in larger fluorescence enhancement and better overridden superradiance thresholds simultaneously. Both phenomena are the best optimized in a six color centers seeded ellipsoidal bare nanoresonator according to the pronounced bad-cavity characteristics. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Superradiant diamond color center arrays coupled to concave plasmonic nanoresonators

Superradiantly enhanced emission of SiV diamond color centers was achieved via numerically optimized concave plasmonic nanoresonators. Advantages of different numbers of SiV color centers, diamond-silver (bare) and diamond-silver-diamond (coated) core-shell nanoresonator types, spherical and ellipsoidal geometries were compared. Indistinguishable superradiance is reached via four color centers, which is accompanied by line-width narrowing except in a coated ellipsoidal nanoresonator that outperforms its bare counterpart in superradiance. Seeding of both spherical and bare ellipsoidal nano-resonators with six color centers results in larger fluorescence enhancement and better overridden superradiance thresholds simultaneously. Both phenomena are the best optimized in a six color centers seeded ellipsoidal bare nanoresonator according to the pronounced bad-cavity characteristics. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen