Table of contents

Preface

Introduction:

Owing to the unique optical properties of nanometre-scale systems, Nanophotonics has become a very efficient tool to control light-matter interaction beyond the limit of diffraction. Recent developments in this field have shown the immense potential of Nanophotonics to contribute to a wide spectrum of scientific disciplines, ranging from fundamental physics to optical engineering, and from biology to clean energies.

This second edition of the NANOP conference focuses on the transversal nature of Nanophotonics, by offering an international forum on the latest advances in the field from basic to applied research.

NANOP 2017 was held in Barcelona and hosted 215 delegates from 40 different countries.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

We investigate an architecture where a plasmonic vortex excited in a gold surface propagates on an adiabatically tapered magnetic tip and detaches to the far-field while carrying a well-defined optical angular momentum. We analyze the out-coming light and show that, despite generally high losses of flat magnetic surface, our 3D structure exhibits high energy throughput. Moreover, we show that once a magneto-optical activity is activated inside the magnetic tip a modulation of the total power transmittance is possible.

Surface gratings with periodicity of 2 μm and amplitude in the range of 175 and 240 nm were fabricated in a plasticized polyvinylchloride doped with a metalloporphyrin (ZnTPP), via a single laser pulse holographic ablation process. The effect of the laser pulse energy on the profiles of the fabricated surface structure was investigated. The sensing capabilities of the fabricated diffractive structures towards amines (triethylamine, diethylamine) and pyridine vapours were then explored; the holographic structures were exposed to the analyte vapours and changes in the intensity of the diffracted light were monitored in real time at 473 nm. It was demonstrated that surface structures, fabricated in a polymer doped with a metalloporphyrin which acts as analyte receptor, have a potential in sensing application.

Optical absorption (OA) and photoluminescence (PL) spectra of InP/ZnS core/shell nanocrystals with 2.3 nm average size were investigated in the temperature range of 6.5–296 K. Using second derivative spectrophotometry technique energies of the OA transitions at 296 K in quantum dot (QD) solutions and films are evaluated to be E₁ = 2.37, E₂ = 4.10 and E₃ = 4.68 eV. Temperature shifts of the E₁ and E₂ levels are found to result from interaction with effective phonons of 59 and 37 meV energies, respectively. Herewith the 370 meV half-width of the first exciton absorption peak remains constant due to the dominance of inhomogeneous broadening effects caused by QD parameters distribution. Measured PL spectra have a complex structure and can be described in 6.5–296 K range by two independent Gaussian components associated with exciton and defect-related states. In addition, Stokes shift of 320 meV is observed to decrease at T > 200 K. PL thermal quenching analysis in frame of Mott mechanism points to presence of non-radiative relaxation channel with an activation energy of 74 meV.

A dielectric lens placed on a metal-dielectric interface can be used for in-plane focusing of surface plasmon (SP) modes. The propagation behind the lens is usually studied using scalar diffraction theory which is not accurate in nanometer regime and cannot explain the propagation and energy flow of SP modes. Here, we have used vectorial derivation of Huygens- Fresnel principal to calculate the diffracted fields behind the lens in order to study the energy flow of SP modes in a focusing system using the concept of higher order modes.

We determine the microscopic transport parameters that are necessary to describe the diffusion process of the atomic gas in optical speckle. We use the self-consistent theory to calculate the self-energy of the atomic gas. We compute the spectral function numerically by an average over disorder realizations in terms of the Greens function. We focus mainly on the behaviour of the energy distribution of the atoms to estimate a correction to the mobility edge. Our results show that the energy distribution of the atoms locates the mobility edge position under the disorder amplitude. This behaviour changes for each disorder parameter. We conclude that the disorder amplitude potential induced modification of the energy distribution of the atoms that plays a major role for the prediction of the mobility edge.

A bidirectional time wavelength division multiplexing-passive optical network (TWDM-PON) with a centralized light source (CLS) is designed and evaluated. TWDM-PON is the promising solution for PON future expansion and migration. The most important issue that limits optical fiber transmission length is the interferometric noise caused by Rayleigh backscattering (RB). In this study, we demonstrate a TWDM-PON architecture with subcarrier at the remote node (RN) to mitigate the RB effect. A successful transmission with 8 optical channels is achieved using wavelength division multiplexing (WDM). Each optical channel is splitted into 8 time slots to achieve TWDM. The proposed scheme is operated over 20 km bidirectional single mode fiber (SMF). The proposed system has the advantage of expanding the downstream (DS) capacity to be 160 Gb/s (8 channels×20 Gb/s) and 20 Gb/s (8 channels×2.5 Gb/s) for the upstream (US) transmission capacity. This is accomplished by a remarkable bit error rate (BER) and low complexity.

We study the properties of luminescent diamond particles of different sizes (up to ~1.5 μm) containing multiple NV-centers. We theoretically predict that the average liftetime in such particles is decreased by several times as compared to optically small subwavelength nanodiamonds. In our experiments, samples were obtained by milling the plasma-enhanced chemical vapor deposited diamond film, and characterized by Raman spectroscopy and dark- field spectroscopy methods. Time-resolved luminescence measurements of the excited state of NV-centers showed that their average lifetime varies from 10 to 17 ns in different samples. By comparing this data to the values of the lifetime of the NV-centers in optically small nanodiamonds, known from literature, we confirm a severalfold decrease of the lifetime in resonant particles.

Aimed to improve the flexibility of optical network-on-a-chip topologies, unguided optical interconnects using plasmonic nanoantennas or dielectric phased arrays have been proposed. However, the bulky footprints of the latter, and both the low directivity figures and high losses of the former, together with complicated excitation schemes, limit their use for on-chip optical interconnects. Here, we introduce a novel concept of on-chip CMOS-compatible wireless optical system based on the use of smartly-engineered broadband easily-fed antennas, which not only overcomes the aforementioned drawbacks but also opens a wide range of applications in several fields. To illustrate its potential, several unprecedented on-chip wireless applications are outlined and experimentally demonstrated. This includes the verification of broadband highly-directive wireless data transmission at speeds as high as 160 Gbit·s⁻¹ over mm-scale links, the realization of fully-reconfigurable wireless beam steering device and the validation of an ultra-compact integrated contactless microflow cytometer.

The formation of complex defects (gallium, arsenic and aluminium vacancies with corresponding interstitial atoms) present at the GaAs/Al_0.3Ga_0.7As heterointerface as well as passivation of the defects by silicon impurities are discussed in the report. We used the density functional theory calculations, with the hybrid functionals B3LYP with Hay-Wadt effective core potentials for all the heavy atoms, in combination with Hay-Wadt valence basis. We present the energy characteristics (formation energy) and geometry of the defects (spatial distribution of the atoms and its charge near the interface defect).

The backlight unit spectrum of liquid crystal displays (LCD) directly affects the colour gamut. With the invention of GaN based blue light emitting diodes (LED), phosphors and quantum dots (QD) have gained considerable scientific interest due to their broad range of applications especially in lighting and display technologies. These phosphors and QDs are used to convert the blue light of the LEDs into white in general lighting. On the other hand, in display systems, they are used to generate red and green bands. There are different application methods such as on-chip and remote configurations. In this study, we concentrate on remote phosphor and QD backlight configurations where the light conversion is done away from the chips. In our display designs, we used GaN based blue LED lateral chips as an excitation source, on the other hand, light conversion layers were placed in backlight units as a thin film for the emission of green and red bands. The mixing ratios of these composite layers were arranged to match the emission spectrum of the blue LEDs and the light conversion layer to the colour filters of the LCD, so that the green, blue, and red bands efficiently widens the colour space. The results were also compared with the on-chip phosphor arrangements.

Double-pulse laser excitation of the eosin and silver nanoparticles embedded into polymer media is known to be a method of electronic-vibrational energy deactivation kinetic process information obtaining and polymer thermal dynamics investigation. We have studied the vibrational relaxation processes in dye molecules (eosin) and nanoparticles in polyvinyl alcohol after two time-shifted laser pulses with fast and delayed fluorescence kinetics study. In order to simulate thermal and photophysical processes caused by double photon excitation, we solved heat transfer and energy deactivation differential equations numerically. The simulation allowed us to obtain the value of heat conductivity coefficient of polymer matrix.

We investigate the changes in the energy spectrum of the graphene monolayer subjected to linear polarised laser beam and external periodically modulated static field (electric and magnetic). Floquet theory and the resonance approximation are used to analyse the energy spectrum and, in particular, the creation and the destruction of the Dirac-Weyl points. We found that at certain conditions the graphene is transformed into the two-dimensional Weyl metals, where each of the two original graphene Dirac cones is split into pairs of the Weyl cones. We also show that altering the laser's beam incidence(tilting) angle may lead to appearing and disappearing of the pairs of Weyl points, the opening gap in the spectrum, and its efficient manipulation.

The comparison and correlation of morphological, optical and crystallographic properties of ultra-thin Au films obtained using field-emission scanning electron microscopy (FESEM), x-ray reflectivity (XRR), UV-visible transmission, and grazing incidence x-ray diffraction (GIXRD) are presented. The Au thin films of different thickness are grown on the glass substrate using the sputtering technique. The particle size, number density and the covered area fraction of Au thin film are obtained from FESEM images. The XRR technique is used to determine the film thickness and surface roughness. The localized surface plasmon resonance (LSPR) response of Au thin films is obtained using UV-Vis transmission spectroscopy. The LSPR peak position and its strength are correlated with film morphology and thickness. Finally, it is shown that LSPR based spectroscopy techniques can provide much better information about morphology and thickness of the Au films up to a resolution of ~1 nm.

Silicon oxycarbide thin films deposited with rf reactive magnetron sputtering a SiC target are exploited to demonstrate photonic waveguides with a high refractive index of 1.82 yielding an index contrast of 18% with silica glass. The propagation losses of the photonic waveguides are measured at the telecom wavelength of 1.55 μm by cut-back technique. The results demonstrate the potential of silicon oxycarbide for photonic applications.