This PDF file contains the front matter associated with SPIE Proceedings Volume 10356, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Enhancing the optical fields near metal nanostructures is of high importance for sensing, energy harvesting and improving the efficiency of optoelectronic devices. Surface enhanced spectroscopies such as Raman scattering (SERS), fluorescence (SEF) and infrared absorption (SEIRA) are enhanced significantly thus allowing lower detection limit and suprresolved imaging. Solar energy harvesting can be improved by designing structures that enhance the local optical field over wide spectral and angular ranges covering the whole solar spectrum. Detectors for the short wave and mid-IR ranges with higher efficiencies started to appear following an optimum designs incorporating plasmonic nanostructures. During the last few years we have been investigating several plasmonic nanostructured thin films for improved biosensors and lately for energy harvesting devices using variety of configurations: standard Kretchmann-Raether configuration, grating coupling, free space excitation of localized plasmons (LSPs) from nanosculptured thin films, and lately excitation of LSPs via extended surface plasmons (ESPs). The later configuration was shown both theoretically and experimentally (using SEF and SERS) to reveal extraordinary enhancement when the matching conditions between the ESP and the LSP are met. Several configurations for improved SPR biosensors and ultrahigh enhancement of local optical fields will be presented with the potential applications in sensing, solar energy harvesting and optoelectronic devices. Acknowledgments: This research was conducted partially by NTU-HUJ-BGU Nanomaterials for Energy and Water Management Programme under the Campus for Research Excellence and Technological Enterprise (CREATE), that is supported by the National Research Foundation, Prime Minister’s Office, Singapore. References 1. Atef Shalabney, C. Khare, Jens Bauer, B. Rauschenbach, and I. Abdulhalim, J. Nanophoton. 6 (1), 061605 (2012). 2. Alina Karabchevsky, Chinmay Khare, Bernd Rauschenbach, and I. Abdulhalim, J. NanoPhotonics 6, 061508-1, 12pp (2012). 3. I. Abdulhalim, Small 10, 3499-3514 (2014). 4. S.K. Srivastava, A. Shalabney, I. Khalaila, C. Grüner, B. Rauschenbach, and I. Abdulhalim, Small 10, 3579-3587 (2014). 5. Sachin K. Srivastava, H. Ben Hamo, A. Kushmaro, R. S. Marks, C. Gruner, B. Rauschenbach and I. Abdulhalim, Analyst, 140, 3201-3209 (2015). 6. Sachin K. Srivastava, C. Grüner, D. Hirsch, B. Rauschenbach, and I. Abdulhalim, Opt. Exp., Accepted (2017). 7. Anran Li, Sivan Isaacs, Ibrahim Abdulhalim, Shuzhou Li, J. Phys. Chem. C 119, 19382-9 (2015). 8. Anran Li, Sachin Srivastava, Ibrahim Abdulhalim, Shuzhou Li, Nanoscale 8, 15658-664 (2016). 9. Sachin K. Srivastava, Anran Li, Shuzhou Li, Ibrahim Abdulhalim, J. Phys. Chem. C 120, 28735-42 (2016).

Sculptured porous Bragg Microcavities (BMs) formed by the successive stacking of columnar SiO₂ and TiO₂ thin films with zig-zag columnar microstructure are prepared by glancing angle deposition. These BMs act as wavelength dependent optical retarders. This optical behavior is attributed to a self-structuration mechanism involving a fence-bundling association of nanocolumns as observed by Focused Ion Beam Scanning Electron Microscopy. The retardance of these optically active BMs can be modulated by dynamic infiltration of their open porosity with vapors, liquids or solutions with different refractive indices. The tunable birefringence of these nanostructured photonic systems have been successfully simulated with a simple model that assumes that each layer within the BMs stack has uniaxial birefringence. This type of self-associated nanostructures has been incorporated to microfluidic chips for free label vapor and liquid sensing. Several examples of the detection performance of these chips, working either in reflection or transmission configuration, for the optical characterization of vapor and liquids of different refractive index and aqueous solutions of glucose flowing through the microfluidic chips are described.

A multilayer that comprises ultra-thin metal and dielectric films has been investigated and applied as a layered metamaterial. By arranging metal and dielectric films alternatively and symmetrically, the equivalent admittance and refractive index can be tailored separately. The tailored admittance and refractive index enable us to design optical filters with more flexibility. The admittance matching is achieved via the admittance tracing in the normalized admittance diagram. In this work, an ultra-thin light absorber is designed as a multilayer composed of one or several cells. Each cell is a seven-layered film stack here. The design concept is to have the extinction as large as possible under the condition of admittance matching. For a seven-layered symmetrical film stack arranged as Ta₂O₅ (45 nm)/ a-Si (17 nm)/ Cr (30 nm)/ Al (30 nm)/ Cr (30 nm)/ a-Si (17 nm)/ Ta₂O₅ (45 nm), its mean equivalent admittance and extinction coefficient over the visible regime is 1.4+0.2i and 2.15, respectively. The unit cell on a transparent BK7 glass substrate absorbs 99% of normally incident light energy for the incident medium is glass. On the other hand, a transmission-induced metal-dielectric film stack is investigated by using the admittance matching method. The equivalent anisotropic property of the metal-dielectric multilayer varied with wavelength and nanostructure are investigated here.

Non-linear optical behavior can be obtained in materials exposed to laser radiation. There are no much results of these properties as function of the structure of the samples. In our case we prepared SiO₂;DR1 amorphous samples by sol-gel method, and mesostructured ones by using cethylmethyamonium bromide (CTAB). The hexagonal structure was evidenced by X-ray diffraction. The transmittance of a focused Helium-Neon 394nm laser light was studied in these samples when moving around the focal point. With the results and using the Sheik-Bahae model the third order nonlinear optical absorption coefficient β and refractive index n₂ were obtained. The dependence of β as function of the laser power can be fit with an exponential curve that reaches saturation. It is clear the hexagonal structured helps to increase the sensitivity of the sample. In the case of the refractive index as function of the laser power the response is similar, but in this case the mesostructure does not give a strong difference.

Epsilon-near-zero (ENZ) metamaterials have been studied in various research areas such as wavefront engineering, supercoupling effect, strong coupling, nonlinear optics, and perfect absorption. An ideal ENZ material of ε=0 is highly omnireflective at any angle of incidence. For a real ENZ material of Re(ε)≈0 the imaginary part Im(ε) is not zero from the causality principle. At an ENZ wavelength at Re(ε)≈0, the normal electric field (E_z ) in an ENZ thin film with a very small Im(ε) becomes very strong and the group velocity slows down; E_z is inversely proportional to the thickness of the film and the imaginary part of ε, resulting in a large light absorption in a low optical loss ENZ thin film. We investigate the tunable ENZ wavelength of indium tin oxide (ITO) thin films in the NIR wavelength regime which are controlled by the film growth conditions and demonstrate the broadband perfect absorption (PA) using the ITO multilayers of different ENZ wavelengths. Coherent perfect absorption (CPA) is an optical phenomenon occurring in an absorbing thin film by the interaction of two counter-propagating coherent waves. We propose a new broadband CPA scheme based on ENZ multilayer films and investigate the multi-wavelength optical switching, indicating that the on- and off-states can be controlled by the phase shift and wavelength of the two incident waves. In this lecture we provide design principles and fabrication guidelines for thin film ENZ devices for PA and CPA, which can find various applications in optical switches, modulators, filters, sensors, and energy harvesting devices.

A novel nanostructured end cap for a truncated conical apex of optical fiber has been studied experimental and numerically. The peculiar cap is composed of asymmetric metal-insulator-metal (MIM) structure coupled with subwavelength holes. The MIM structure may act as reflective band cut filter or generator of surface plasmon polariton (SPP). And nano holes in the thicker metal layer could extract the SPP from the MIM structure and lead it to outer surface of the metal layer. For the purpose, the author has started to create the asymmetric MIM structure with TiN and AlN by pulsed laser deposition (PLD). The resultant structure was diagnosed by spectroscopic analyses.

Cermet coatings based on nanoparticles of Au or Ag in a stable dielectric matrix provide a combination of spectral-selectivity and microstructural stability at elevated temperatures. The nanoparticles provide an absorption peak due to their localized surface plasmon resonance and the dielectric matrix provides red-shifting and intrinsic absorption from defects. The matrix and two separated cermet layers combined add mechanical support, greater thermal stability and extra absorptance. The coatings may be prepared by magnetron sputtering. They have solar absorptance ranging between 91% and 97% with low thermal emittance making them suitable for application in solar thermal conversion installations.

Light management is a key issue for highly efficient liquid-phase crystallized silicon (LPC-Si) thin-film solar cells and can be achieved with periodic nanotextures. They are fabricated with nanoimprint lithography and situated between the glass superstrate and the silicon absorber. To combine excellent optical performance and LPC-Si material quality leading to open circuit voltages exceeding 640 mV, the nanotextures must be smooth. Optical simulations of these solar cells can be performed with the finite element method (FEM). Accurately simulating the optics of such layer stacks requires not only to consider the nanotextured glass-silicon interface, but also to adequately account for the air-glass interface on top of this stack. When using rigorous Maxwell solvers like the finite element method (FEM), the air-glass interface has to be taken into account a posteriori, because the solar cells are prepared on thick glass superstrates, in which light is to be treated incoherently. In this contribution we discuss two different incoherent a posteriori corrections, which we test for nanotextures between glass and silicon. A comparison with experimental data reveals that a first-order correction can predict the measured reflectivity of the samples much better than an often-applied zeroth-order correction.

Metasurfaces are the bidimensional analog of metamaterials. There are made of resonant elements deposited on a thin film. They have been shown to allow for the control of polarization of light, in particular through topological effects and to make possible the transmission of a light beam under generalized refraction laws. In the present work, metasurfaces whose period is made of several resonant elements with both electric and magnetic dipoles are considered. A general theory of diffraction is developed and the possibility of optimization towards designing a predefined wavefront are investigated. To do so, we use multiple scattering theory as well as a singular perturbation approach that allows us to obtain a simple setting of the scattering problem in terms of a generalized impedance operator. This formulation is then used within an optimization algorithm in order to investigate the range of parameters over which a fine control of the transmitted beam can be obtained.

Three numerical studies were undertaken involving the interactions of plane waves with topological insulators. In each study, the topologically insulating surface states of the topological insulator were represented through a surface admittance. Canonical boundary-value problems were solved for the following cases: (i) Dyakonov surface-wave propagation guided by the planar interface of a columnar thin film and an isotropic dielectric topological insulator; (ii) Dyakonov–Tamm surface-wave propagation guided by the planar interface of a structurally chiral material and an isotropic dielectric topological insulator; and (iii) reflection and transmission due to the planar interface of a topologically insulating columnar thin film and vacuum. The nonzero surface admittance resulted in asymmetries in the wave speeds and decay constants of the surface waves in studies (i) and (ii). The nonzero surface admittance resulted in asymmetries in the reflectances and transmittances in study (iii).

The rigorous coupled-wave approach (RCWA) was used to calculate the optical absorption in a dielectric material deposited over a two-dimensional (2D) metallic surface-relief grating. The dielectric material was taken to be nonhomogeneous in the direction normal to the mean plane of the grating. The grating was chosen to comprise hillocks on a square grid. On illumination by a monochromatic plane waves, the chosen structure should support the excitation of two types of guided-wave modes: surface-plasmon-polariton (SPP) waves and waveguide modes (WGMs). Two cases were considered: (i) a 1D photonic crystal made from layers of silicon oxynitrides of differing composition, and (ii) a tandem solar cell comprising three amorphous-silicon p-i-n junctions. Optical absorption was studied in relation to the direction of propagation, polarization state, and the free-space wavelength of the incident plane wave. Several but not all absorptance peaks were correlated with the excitations of SPP-wave modes and WGMs predicted by the solutions of the underlying canonical boundary-value problems for guided-wave propagation. Some peaks of useful absorptances in the solar cell were also predicted by solutions of the canonical problems.

Laser resistance of optical elements is one of the major topics in photonics. Various routes have been taken to improve optical coatings, including, but not limited by, materials engineering and optimisation of electric field distribution in multilayers. During the decades of research, it was found, that high band-gap materials, such as silica, are highly resistant to laser light. Unfortunately, only the production of anti-reflection coatings of all-silica materials are presented to this day. A novel route will be presented in materials engineering, capable to manufacture high reflection optical elements using only SiO₂ material and GLancing Angle Deposition (GLAD) method. The technique involves the deposition of columnar structure and tailoring the refractive index of silica material throughout the coating thickness. A numerous analysis indicate the superior properties of GLAD coatings when compared with standard methods for Bragg mirrors production. Several groups of optical components are presented including anti-reflection coatings and Bragg mirrors. Structural and optical characterisation of the method have been performed and compared with standard methods. All researches indicate the possibility of new generation coatings for high power laser systems.

Angled columnar structures produced by oblique angle deposition possess useful optical polarization effects. It is well known that this is due to structural anisotropy but the relative contributions of factors affecting this anisotropy are not fully understood in all cases. Serial bideposited films where the azimuth is changed during deposition can have greater birefringence if the azimuths are directly opposed. In contrast, in this article the properties of perpendicular azimuth films are studied: silicon films at tilt angles 50-80° were deposited and analyzed. Electron microscopy confirmed that the silicon nanostructures were formed off-axis, meaning they did not develop along the deposition axes but followed the averaged azimuth. Optical measurements confirm that the maximum birefringence occurs closer to glancing angles, and optical modelling demonstrates that in contrast to fixed azimuth films the birefringence in these perpendicular azimuth films is primarily modulated by depolarization factors.

A promising fabrication method for graphene is the reduction of graphene oxide (GO), this can be achieved photochemically by laser irradiation. In this study, we examine the results of latter method by a femtosecond fiber laser (1030 nm, 280 fs). The chemical properties of the irradiated areas were analyzed by Raman and X-ray photoelectron spectroscopy (XPS) and electrical properties were evaluated using sheet resistance measurements. We found that, within a wide range of fluences (8.5 mJ/cm² to 57.8 mJ/cm²) at high overlapping rates (>99.45 %), photochemical oxygen reduction can be achieved. However, hybridization transition of sp³ to sp² graphene-like structures only takes place at upper fluences of the mentioned range.

We review properties of 1D and 2D resonant silicon metasurfaces based on fundamental electromagnetic resonance effects in thin periodic films. The spectral response upon transition from zero-contrast to high-contrast grating interfaces is explored. We discuss design and optimization with rigorous mathematical methods and review typical fabrication processes. New theoretical and experimental results for numerous devices are furnished. These include wideband reflectors and flat-top bandpass filters with multi-module resonant structures. The guided-mode resonance concept applies in all spectral regions, from the visible band to the microwave domain, with available low-loss materials.

Protective nitrogen doped Si-C multilayer coatings on carbon, used to improve the oxidation resistance of carbon, were obtained by Thermionic Vacuum Arc (TVA) method. The initial carbon layer having a thickness of 100nm has been deposed on a silicon substrate in the absence of nitrogen, and then a 3nm Si thin film to cover carbon layer was deposed. Further, seven Si and C layers were alternatively deposed in the presence of nitrogen ions, each having a thickness of 40nm. In order to form silicon carbide at the interface between silicon and carbon layers, all carbon, silicon and nitrogen ions energy has increased up to 150eV . The characterization of microstructure and electrical properties of as-prepared N-Si-C multilayer structures were done using Transmission Electron Microscopy (TEM, STEM) techniques, Thermal Desorption Spectroscopy (TDS) and electrical measurements. Oxidation protection of carbon is based on the reaction between oxygen and silicon carbide, resulting in SiO₂, SiO and CO₂, and also by reaction involving N, O and Si, resulting in silicon oxynitride (SiN_xO_y) with a continuously variable composition, and on the other hand, since nitrogen acts as a trapping barrier for oxygen. To perform electrical measurements, 80% silver filled two-component epoxy-based glue ohmic contacts were attached on the N-Si-C samples. Electrical conductivity was measured in constant current mode. The experimental data show the increase of conductivity with the increase of the nitrogen content. To explain the temperature behavior of electrical conductivity we assumed a thermally activated electric transport mechanism.

Optical elements for polarization control are one of the main parts in advanced laser systems. The state and intensity of polarized light is typically controlled by optical elements, namely waveplates. Polymers, solid or liquid crystals and other materials with anisotropic refractive index can be used for production of waveplates. Unfortunately, most of aforementioned materials are fragile, unstable when environmental conditions changes, difficult to apply in microsystems and has low resistance to laser radiation. Retarders, fabricated by evaporation process, do not consist any of these drawbacks. In order to manufacture such optical components with high quality, characterisation of deposition parameters are essential. A serial bi-deposition method was employed to coat anisotropic layers for polarisation control. Such waveplate can be deposited on micro optics or other optical elements, essentially improving compact optical systems. The range of available materials is limited by absorption losses for waveplates in UV spectral region. Therefore, the investigation was accomplished with four eligible candidates – TiO₂, LaF₃, Al₂O₃ and SiO₂. Structural (XPS, XRD) and optical (spectrophotometry, ellipsometry) analysis have shown Al₂O₃ and SiO₂ as the most applicable materials for UV spectral region.

The main purpose of this study is to develop a batch producible hot embossing 3D nanostructured surface-enhanced Raman chip technology for high sensitivity label-free plasticizer detection. This study utilizing the AAO self-assembled uniform nano-hemispherical array barrier layer as a template to create a durable nanostructured nickel mold. With the hot embossing technique and the durable nanostructured nickel mold, we are able to batch produce the 3D Nanostructured Surface-enhanced Raman Scattering Chip with consistent quality. In addition, because of our SERS chip can be fabricated by batch processing, the fabrication cost is low. Therefore, the developed method is very promising to be widespread and extensively used in rapid chemical and biomolecular detection applications.

For the sol-gel method, it is still challenging to achieve excellent spectral performance when preparing antireflection (AR) coating by this way. The difficulty lies in controlling the film thickness accurately. To correct the thickness error of sol-gel coating, a hybrid approach that combined conventional sol-gel process with ion-beam etching technology was proposed in this work. The etching rate was carefully adjusted and calibrated to a relatively low value for removing the redundant material. Using atomic force microscope (AFM), it has been demonstrated that film surface morphology will not be changed in this process. After correcting the thickness error, an AR coating working at 1064 nm was prepared with transmittance higher than 99.5%.

Temperature-induced changes in the propagation of electromagnetic surface waves guided by the planar interface of a temperature-sensitive isotropic material (namely, InSb) and a temperature-insensitive anisotropic material were investigated theoretically in the terahertz frequency regime. Two types of anisotropic partnering material were considered: (i) a homogeneous material and (ii) a periodically nonhomogeneous material. As the temperature increases, the isotropic partnering material is transformed from a weakly dissipative dielectric material to a plasmonic material. As a consequence, the surface waves change from Dyakonov surface waves to surface-plasmon-polariton waves for case (i), and change from Dyakonov–Tamm surface waves to surfaceplasmon-polariton waves for case (ii). Numerical investigations demonstrated that dramatic changes in the numbers of propagating Dyakonov or Dyakonov–Tamm surface waves, their angular existence domains, their propagation constants, and their decay constants, could arise from modest changes in temperature.

The unit cell of a chevronic sculptured thin film (ChevSTF) comprises two identical columnar thin films (CTFs) except that the nanocolumns of the first are oriented at an angle Χ and nanocolumns of the second are oriented at an angle π − χ with respect to the interface of the two CTFs. A ChevSTF containing 10 unit cells was fabricated and its planewave reflectance and transmittance spectrums of this ChevSTF were measured. Despite its structural periodicity, the ChevSTF did not exhibit the Bragg phenomenon. Theoretical calculations with the CTFs modeled as biaxial dielectric materials indicated that the Bragg phenomenon would not be manifested for normal and near-normal incidence, but vestigial manifestation was possible for sufficiently oblique incidence.

An ideal light-absorbing surface is able to collect light energy from wide ranges of wavelengths and angles of incidence. It has been reported that photonic structures can manipulate and couple light on the nanoscale surface. These photonic nanostructures can enhance light absorption and improve solar energy conversion also have been expected. In this article, we will describe how to calculate the optical properties of photonic nanostructures, especially for the biomimetic antireflecting structures on semiconductor substrates. The optical properties of biomimetic nanostructures were been analyzed using finite difference time domain (FDTD) calculations. Our FDTD simulation results show that the antireflecting structures utilize design parameters of spacing/wavelength and length/spacing, which could be expected exhibiting ∼99% optical absorption over wavelength from UV-vis region and angle of incidence up to 60° in high-index semiconductor materials.