N. Papanikolaou

National Center for Scientific Research Demokritos | ncsr · Institute of Nanoscience and Nanotechnology

Metamaterials are a fascinating class of photonic materials since they allow us to control optical responses (largely) at will. Besides being an intellectual challenge, adding time variations into spatial metamaterials increases the degrees of freedom to tune their effective response, which motivates their exploration. However, to exploit such mate...

A proper generalization of the extended boundary condition method to calculate the transition matrix, T , for electromagnetic scattering from a homogeneous and isotropic body of arbitrary shape, characterized by a periodically time-varying electric permittivity, is presented. The application of the method on a specific example of a spheroidal diele...

Early diagnosis and monitoring are essential for the effective treatment and survival of patients with different types of malignancy. To this end, the accurate and sensitive determination of substances in human biological fluids related to cancer diagnosis and/or prognosis, i.e., cancer biomarkers, is of ultimate importance. Advancements in the fie...

Citation: Geka, G.; Kanioura, A.; Kochylas, I.; Likodimos, V.; Gardelis, S.; Chatzantonaki, K.; Charvalos, E.; Dimitriou, A.; Papanikolaou, N.; Economou, A.; et al. Immunosensing Cancer Markers through Surface-Enhanced Photoluminescence on Nanostructured Silver Substrates. Eng. Proc. 2023, 35, 7. https:// Abstract: Noble metal nanostructured substr...

An extension of the photonic layer multiple scattering methodology to dynamic spherical scatterers, which exhibit a periodic time‐varying response, is presented. The applicability of the method is demonstrated on specific examples of single‐ and bi‐layers of periodically modulated high‐refractive‐index spherical particles arranged on a square latti...

Glutathione and malondialdehyde are two compounds commonly used to evaluate the oxidative stress status of an organism. Although their determination is usually performed in blood serum, saliva is gaining ground as the biological fluid of choice for oxidative stress determination at the point of need. For this purpose, surface-enhanced Raman spectro...

Citation: Kochylas, I.; Dimitriou, A.; Apostolaki, M.-A.; Skoulikidou, M.-C.; Likodimos, V.; Gardelis, S.; Papanikolaou, N. Enhanced Abstract: In this study, we developed active substrates consisting of Ag-decorated silicon nanowires on a Si substrate using a single-step Metal Assisted Chemical Etching (MACE) process, and evaluated their performanc...

This work reports on light scattering by a homogeneous dielectric sphere with a periodically time-varying radius. The off-shell inelastic scattering T matrix, which describes the dynamically changing particle, is evaluated using the Floquet method, and some remarkable phenomena, emerging in the strong- and weak-coupling regimes, are discussed. In p...

A novel optical label-free biosensing approach is introduced aiming to remove the current limitations of optical biosensors in their application of on-site food analysis. The proposed methodology (GRADual thin film IntErferometry, GRADE) is based on light interferometry employing an illumination source of a few nm spectral width and a 3D micro-patt...

We study magnon-mediated optical transitions in micrometer-sized axially symmetric yttrium iron garnet (YIG) particles, which act as optomagnonic cavities, by means of electromagnetic calculations, treating the magneto-optical coupling to first order in perturbation theory, in the framework of a fully dynamic approach. Such particles with engineere...

In this chapter, we focus our attention on the optical properties of statically and dynamically magnetized spherical dielectric resonators in the visible/near-infrared part of the spectrum. First, we elaborate on essential definitions and mathematical tools for dealing with the electromagnetic response of a homogeneous unmagnetized sphere. Next, we...

Flexible barrier films that resist to gas permeation have a wide range of applications in various industrial sectors, from food packaging to electronics and aerospace. Especially for the latter, it is important to use lightweight materials that demonstrate sufficient diffusion resistance. Thermoplastic Polyurethane (TPU) films are widely used in th...

A thorough theoretical study of the optical properties of periodic Si nanosphere arrays is undertaken, placing a particular emphasis on the synergy between multipolar, electric and magnetic, Mie resonances, which occur in high-refractive-index nanoparticles and can lead to a rich variety of phenomena ranging from perfect reflection to controlled di...

The optimization of the development conditions in a lithography process is crucial for the overall lithographic performance while the study of the development step provides useful information regarding the properties of the lithographic material. In this work, high resolution e-beam resists are studied through in-situ monitoring of resist thickness...

We report a thorough theoretical investigation of magnon-assisted photon transitions in magnetic garnet micron-sized spheres, which operate as optomagnonic resonators. In this case, matching the intraband splitting of optical Mie modes, induced by particle magnetization, to the eigenfrequency of the uniform-precession spin wave, high-efficiency tri...

A thorough theoretical study of the optical properties of periodic Si nanosphere arrays is undertaken, placing particular emphasis on the synergy between electric and magnetic Mie resonances, which occur in high-refractive-index nanoparticles and can lead to a rich variety of phenomena ranging from perfect reflection to controlled diffraction. By m...

In polymer coated planar Inter Digitated Electrodes (IDEs), the gas sensing sensitivity is much lower than the sensitivity of parallel plate capacitors. Here, we introduce a simple patterning step for the modification of the geometry of the dielectric substrate of the planar IDEs, and increase of the contribution of the sensitive layer to the outpu...

We report on judiciously designed strati ed periodic structures of magnetic dielectric materials with a localized defect layer, which are able to concurrently confine light and spin waves in the same ultra-small defect region for a long time period, thus resulting in enhanced photon-magnon interaction and large dynamic optical frequency shift. Our...

We report on periodic structures of dielectric magnetic layers with a localized defect that confines light and spin waves, resulting in enhanced interaction and dynamical optical frequency shift through multi-magnon absorption/emission processes.

The interaction of visible and near-infrared light with spin waves in appropriately designed dual nanocavities, for both photons and magnons, is investigated by means of rigorous calculations, correct to arbitrary order in the magneto-optical coupling parameter. It is shown that the concurrent localization of the interacting photon and magnon field...

The magneto-optical response of a Faraday-active Fabry-Pérot etalon with birefringent mirrors is studied by means of electrodynamic simulations using the finite-element and the scattering-matrix methods. The specific structure under consideration consists of a magnetic garnet film sandwiched between two metallic layers, patterned with periodically...

We developed an extension of the layer-multiple-scattering method to photonic crystals comprising homogeneous layers of magneto-optical materials. The applicability of the method is demonstrated on a specific architecture of a magnetic garnet thin film coated with a square array of silver nanodisks, supported by a silica substrate. It is shown that...

In this paper we present a theoretical study of dielectric nanostructures capable for localizing light in subwavelength volumes. These are arrays of Si nanoparticles on top of reflecting substrates, which can be properly designed to sustain resonances that confine light outside the particle, near the surface, resulting in increased sensitivity of t...

We report on the influence of elastic waves on the optical response and light emission in simultaneously photonic and phononic resonant cavities. Elastic waves couple with light through the acousto-optic interaction. Concurrent control of both light and sound through simultaneously photonic-phononic, often called phoxonic, band-gap structures is in...

We present a comparative theoretical study of the optical response of metallic Ag and dielectric Si sphere arrays on top of reflecting substrates. The interaction of particle modes with guided modes of the substrate leads to a rich optical spectrum. We design structures that sustain highly concentrated electromagnetic fields around periodic arrays...

Composite magnetoplasmonic nanoparticles with a core-shell morphology exhibit intriguing optical properties and offer impressive opportunities for tailoring in a controllable manner the light-matter interaction at subwavelength dimensions. These properties are usually analyzed in the framework of the quasi-static approximation, which, however, is o...

One-dimensional polymeric photonic crystal (PC) arrays with tuned bandgap properties are designed and fabricated on the same substrate by employing mainstream micropatterning technologies and appropriate photopatternable materials. The two photopatternable materials are based on poly (2-hydroxy ethyl methacrylate) and epoxy polymers with the additi...

In this work we investigate both experimentally and theoretically the optical properties of aligned, perpendicular to the substrate, high aspect ratio (AR), plasma etched Si nanowires (SiNWs) with controlled variability. We focus on the role of imperfections in fabrication, which manifest themselves as dimensional variability of SiNW, lattice defec...

We report on the design, fabrication and characterization of PhC cavities in Si3N4 suspended nanowires. Electromagnetic simulations indicate that the structures are promising to achieve strong light localization in visible and near infrared region.

We report on the design, fabrication and characterization of PhC cavities in Si3N4 suspended nanowires. Electromagnetic simulations indicate that the structures are promising to achieve strong light localization in visible and near infrared region.

The limits of validity of the linear photoelastic model are investigated in a one-dimensional dual photonic-phononic cavity, formed by alternating layers of a chalcogenide glass and a polymer homogeneous and isotropic material, which supports both optical and acoustic resonant modes localized in the same region. It is shown that the linear-response...

The interaction of light and sound waves at the micro and nanoscale has attracted considerable interest in recent years. The main reason is that this interaction is responsible for a wide variety of intriguing physical phenomena, ranging from the laser-induced cooling of a micromechanical resonator down to its ground state to the management of the...

We show that a relatively sparse photonic crystal of high-permittivity magnetic garnet particles can induce a giant Faraday rotation of light transmitted through a finite slab of it. The underlying mechanism resides in wave propagation through collective Bloch modes, which are strongly localized in the particles.

In the present study, a one dimensional polymeric photonic crystal is designed, fabricated and evaluated as a humidity sensor. The polymeric photonic crystal is consisted of a multilayer stack of sequential hydrophobic and hydrophilic layers applied using conventional photolithographic steps: spin-coating and DUV exposure. During exposure in a humi...

By means of full electrodynamic simulations, we investigate structures that can totally absorb light minimizing all reflections. Such efficient absorbers of visible and infrared light are useful in photovoltaic and sensor applications. Our study provides a simple and transparent analysis of the optical properties of structures comprising a resonant...

We study, by means of full-electrodynamic calculations using the layer-multiple-scattering method, the effect of diffractive coupling on the enhancement of the local electromagnetic field in periodic arrays of nanolenses consisting of three silver spheres with progressively decreasing sizes and separations. The interaction between the hot-spot mode...

The modulation of spontaneous light emission of active centers through elastic waves in Si/SiO2 multilayer phoxonic structures that support dual photonic-phononic localized modes, in the bulk or at the surface, is studied by means of rigorous full electrodynamic and elastodynamic calculations. Our results show that strong dynamic modulation of the...

A systematic study, by means of full electrodynamic calculations, of the optical activity of layer-by-layer chiral crystals of finite silver nanorods is presented. The nature of the eigenmodes of the electromagnetic field and the formation of partial gaps for a specific circular polarization in these crystals are analyzed by reference to the hybrid...

Light control through elastic waves is a well established and mature technology. The underlying mechanism is the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately designed structur...

We report on the optical properties of a layer-by-layer structure of silver nanorods, with their axes aligned perpendicular to the z direction and mutually twisted through an angle of 60° from layer to layer, by means of rigorous full electrodynamic calculations using the layer-multiple-scattering method, properly extended to describe axis-symmetri...

Light control through elastic waves is a well established and mature technology. The underlying mechanism is the scattering of light due to the dynamic modulation of the refractive index and the material interfaces caused by an elastic wave, the so-called acousto-optic interaction. This interaction can be enhanced in appropriately designed structur...

We report on the occurrence of strong nonlinear acousto-optic interactions in phoxonic structures, that support, simultaneously, acoustic and optical localized resonant modes, under the influence of acoustic losses. Deploy-ing a detailed theoretical investigation of the acousto-optic coupling in the specific case of a one-dimensional phoxonic cavit...

One dimensional (1D) Photonic crystals (PC) are the simplest form of PC consisting of alternative layers of materials having different refractive indices. This periodic structure has very interesting optical properties allowing manipulation and control of light reflectance wavelength. Polymers have already been used as optical components in several...

We discuss theoretically the simultaneous existence of phoxonic, i.e., dual phononic and photonic, band gaps in a periodic silicon strip waveguide. The unit-cell of this one-dimensional waveguide contains a hole in the middle and two symmetric stubs on the sides. Indeed, stubs and holes are respectively favorable for creating a phononic and a photo...

The fabrication of a power-free, reversible, color-indicator sensor of the relative humidity in the environment has numerous applications and is considered a challenging task. The device to be developed should be able of color changing according to the degree of humidity change and have a number of characteristics, i.e., reversibility, fast respons...

The interaction between acoustic breathing modes and optical Mie resonances in a spherical particle made of a chalcogenide glass material is investigated by means of rigorous calculations, correct to any order in the acousto-optic coupling parameter. Our results reveal the occurrence of strong effects beyond the linear-response approximation, which...

We report on the occurrence and properties of photonic surface states in fcc crystals of metallic nanoshells, by means of full-electrodynamic calculations using the layer-multiple-scattering method, properly extended. Detailed dispersion diagrams of the surface states associated with the (001) and (111) surfaces are calculated for such semi-infinit...

By employing the layer-multiple-scattering method, properly extended to periodic assemblies of arbitrarily oriented axis-symmetric particles, we investigate the optical response of a three-dimensional spiral-staircase structure of metallic nanorods. We show that the combination of plasmonic modes and helical arrangement of the nanorods results in t...

We have fabricated sub-quarter-micron-patterned Au templates with electron beam lithography, and studied their effect on the fluorescence intensity of immobilized, anti-rabbit IgG antibody labeled with AlexaFluor® 546. Varying the geometry of the structured surface, the plasmon resonances are tuned to match the fluorescence wavelengths and achieve...

We present an extension of the layer-multiple-scattering method to phononic crystals of nonspherical particles in a homogeneous host medium by employing the extended-boundary-condition technique for the description of the individual scatterers. The efficiency of the method is demonstrated on specific examples of two- and three-dimensional periodic...

We demonstrate theoretically that photons and acoustic phonons can be simultaneously guided and slowed down in specially designed nanostructures. Phoxonic crystal waveguides presenting simultaneous phononic and photonic band gaps were designed in perforated silicon membranes that can be conveniently obtained using silicon-on-insulator technology. G...

Periodic media offer impressive opportunities to manipulate the transport of classical waves namely light or sound. Elastic waves can scatter light through the so-called acousto-optic interaction which is widely used to control light in telecommunication systems and, additionally, the radiation pressure of light can generate elastic waves. Concurre...

We discuss the simultaneous existence of phoxonic, i.e., phononic and photonic, band gaps in a periodic array of holes drilled in a Si membrane. We investigate in detail both the square and the honeycomb lattices. We show that complete phoxonic band gaps can be obtained with the honeycomb lattice. Otherwise, both structures present the possibility...

By applying a homogenization method based on systematic full-electrodynamic complex-band-structure calculations, we deduce the effective permittivity tensor of a uniaxial photonic crystal consisting of consecutive hexagonal arrays of aligned metallic nanorods of finite length. The form of the obtained permittivity tensor over a relatively broad low...

We report on the occurrence of strong nonlinear acousto-optic interactions in a one-dimensional model phoxonic cavity that supports, simultaneously, photonic and phononic localized resonant modes, by means of rigorous electrodynamic and elastodynamic calculations. We show that these interactions can take place when photons and phonons of long lifet...

We study theoretically the simultaneous existence of phononic and photonic band gaps in a periodic array of silicon pillars deposited on a homogeneous thin silica plate. Several lattices, namely, square, triangular, and honeycomb are investigated for a wide range of geometrical parameters. We discuss the most suitable cases for dual phononic-photon...

We report on the effective optical response of single- and multilayer periodic structures of metallodielectric nanosandwiches on the basis of rigorous, full-electrodynamic calculations by the extended layer-multiple-scattering method. It is shown that the complex photonic band structure and the reflection coefficient of the infinite and semi-infini...

We apply the layer-multiple-scattering method to study the optical properties of different plasmonic architectures; namely two- and three-dimensional periodic arrays of metallic nanocylinders and of metallodielectric nanosandwiches. These structures exhibit various types of collective plasmonic resonances, tunable over a broad spectral range from i...

We discuss the simultaneous existence of phononic and photonic band gaps in a periodic array of holes drilled in a Si membrane. We investigate in detail both the centered square lattice and the boron nitride (BN) lattice with two atoms per unit cell which include the simple square, triangular and honeycomb lattices as particular cases. We show that...

By means of full electrodynamic and elastodynamic multiple-scattering calculations we study the optical and acoustic properties of three-dimensional lattices of metallic nanospheres implanted in a dielectric host. Our results show that such structures exhibit omnidirectional spectral gaps for both telecom infrared light and hypersound, with relativ...