This PDF file contains the front matter associated with SPIE Proceedings Volume 9371 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Progress in understanding resonant subwavelength structures has fueled an explosion of interest in fundamental processes and nanophotonic devices. The carrier density and optical properties of photonic nanostructures are typically fixed at the time of fabrication, but field effect tuning of the potential and carrier density enables the photonic dispersion to be altered, yielding new approaches to energy conversion and tunable radiative emission. Electrochemical in metals yields tunable resonances and reveals the plasmoelectric effect, a newly-discovered photoelectrochemical potential. Finally, while plasmons are usually described in a classical electromagnetic theory context, under single photon excitation quantum coherent states emerge. We demonstrate entanglement or coherent superposition states of single plasmons using two plasmon-quantum interference in chip-based plasmon waveguide directional couplers.

Single-photon sources based on solid-state emitters, like quantum dots, molecules or defect centers in diamond, are one of the key components for an integrated quantum technology. Here, we will show different strategies used in order to integrate single-photon emitters. Among others, we introduce an hybrid approach using photon emission from defect centers in diamond and laser-written photonic structures. Waveguides, microresonators, and optical antennas can be fabricated and oriented with respect to the single emitters. We describe our general approach before we specifically address the problem of efficient single-photon collection through optical antennas. We discuss the limitations of the method, its potential for scalability as well as its extension towards optical sensing applications.

A spatially-variant photonic crystal (SVPC) that can control the spatial propagation of electromagnetic waves in three dimensions with high polarization sensitivity was fabricated and characterized. The geometric attributes of the SVPC lattice were spatially varied to make use of the directional phenomena of self-collimation to tightly bend an unguided beam coherently through a 90 degree angle. Both the lattice spacing and the fill factor of the SVPC were maintained to be nearly constant throughout the structure. A finite-difference frequency-domain computational method confirms that the SVPC can self-collimate and bend light without significant diffuse scatter caused by the bend. The SVPC was fabricated using multi-photon direct laser writing in the photo-polymer SU-8. Mid-infrared light having a vacuum wavelength of λ0 = 2.94 μm was used to experimentally characterize the SVPCs by scanning the sides of the structure with optical fibers and measuring the intensity of light emanating from each face. Results show that the SVPC is capable of directing power flow of one polarization through a 90-degree turn, confirming the self-collimating and polarization selective light-guiding properties of the structures.

Structurally chiral materials exhibit the circular Bragg phenomenon (CBP). These materials preferentially reflect circularly polarized light of the same handedness while transmitting circularly polarized light of the opposite handedness within a range of wavelengths called the circular Bragg regime. The CBP has been extensively investigated experimentally for normal incidence, but not for oblique incidence. After fabricating a 20-periodthick chiral sculptured thin film, we measured all of its circular remittances over a 60◦ range of the angle of incidence and a 300-nm range of the free-space wavelength. Provided the incidence is not very oblique, the obtained dependencies of the center wavelength and the bandwidth of the CBP on the angle of incidence match theoretical estimates.

We demonstrate a facile method for fabrication of colloidal crystals containing a planar defect by using PS@SiO₂ core-shell spheres as building blocks. A monolayer of solid spheres was embedded in core-shell colloidal crystals serving as the defect layer, which formed by means of self-assembly at the air/water interface. Compared with previous methods, this fabrication method results in pronounced passbands in the band gaps of the colloidal photonic crystal. The FWHM of the obtained passband is only ~16nm, which is narrower than the previously reported results. The influence of the defect layer thickness on the optical properties of these sandwiched structures was also investigated. No high-cost processes or specific equipment is needed in our approach. Inverse opals with planar defects can be obtained via calcination of the PS cores, without the need of infiltration. The experimental results are in good agreement with simulations performed using the FDTD method.

The design of metasurfaces able to efficiently control the polarization state of an electromagnetic wave is of importance for various applications. We demonstrate both theoretically and experimentally that plasmonic planar L-shaped antennas can induce a 90° -rotation of the linear polarization of light with a nearly total efficiency in the infrared (3-5 µm). The influence of the in-plane geometry of the nanoantenna is investigated, and it is shown that it can be engineered so that the polarization conversion occurs over a 1 µm-wide spectral band ([3.25-4.25] µm) with a mean polarization conversion efficiency of 95%. These results are experimentally confirmed on two samples with distinctive geometries.

We investigate negative index of refraction in plasmonic metamaterials with an emphasis on distinguishing and isolating contributions to negative refraction from spatial dispersion, as a function of metamaterial dimensions on the scale of the wavelength. We explain the design approach using genetic algorithm and provide sample applications including negative refraction.

Metamaterials are artificial structures with exotic electromagnetic response: negative refraction, sub-wavelength focusing, and so on. Although characteristics of metamaterials are almost determined by unit cell structure, coupling effects among unit cells also have an important role in engineering electromagnetic response of metamaterials. In this study, we investigated Q-factors of Fano resonance in optical metamaterials having alternate arrangement of inversed asymmetric double bars (ADBs) to study effects of neighboring unit cell. An ADB is a pair of metal bars with slightly different bar lengths. Fano resonance with a high Q-factor was excited because of small asymmetry of an ADB. Alternate arrangement of inversed unit cells, in which the positions of the long bar and the short bar in neighboring unit cells were interchanged each other, was introduced into ADB metamaterials and its effect on the Q-factor was investigated. ADB metamaterials were fabricated by a lift-off method and optical spectra were measured. The Q-factors of Fano resonance around a wavelength of 1500 nm were estimated from absorption peaks, and dependence of a degree of asymmetry was studied. The Q-factor had strong dependence of asymmetry. Moreover, the Q-factors for alternate arrangement of inversed unit cells were higher than that for normally periodic arrangement. The enhancement is qualitatively expressed by interaction of magnetic dipoles among neighboring unit cells.

Epsilon-near-zero metamaterial samples, composed of five alternating bi-layers of silica and silver, are fabricated using the electron-beam evaporator. Nonlinear properties of samples are measured using a pulsed Ti:sapphire laser by the z-scan technique. It is observed that the real part of the nonlinear Kerr index is one order of magnitude higher than the values expected from a naive averaging of the corresponding coefficients of metal and dielectric layers (the correct averaging should be performed with respect to the nonlinear susceptibility), so that its value is actually of the same order of magnitude as that of a single silver layer. At the same time, the transmission of our samples is remarkably higher than that of a single silver layer of the same thickness. These characteristics have a great impact on the amount of optical energy which can be pumped into the structure, thus allowing its nonlinear properties to be accumulated over long propagation distance along the sample. This property is very promising for applications, which are based on the modulation of phase, amplitude or frequency of light, especially those which require low-power operations, such as all-optical switching and memory elements.

Flexible metamaterials (FMMs) at optical frequencies can conform to a wide range of target geometries whilst allowing their optical properties to be tuned post-fabrication. Here we discuss this potential by presenting our recent and preliminary results, obtained for FMMs at visible frequencies for sensing, filtering and imaging applications.

Despite much interest and progress in optical spatial cloaking, a three-dimensional (3D), transmitting, continuously multidirectional cloak in the visible regime has not yet been demonstrated. Here we experimentally demonstrate such a cloak using ray optics, albeit with some edge effects. Our device requires no new materials, uses isotropic off-the-shelf optics, scales easily to cloak arbitrarily large objects, and is as broadband as the choice of optical material, all of which have been challenges for current cloaking schemes. In addition, we provide a concise formalism that quantifies and produces perfect optical cloaks in the small-angle (`paraxial') limit.

In this work, we study how the Orbital Angular Momentum of a Plasmonic Vortex (an SPP carrying OAM) can be probed by the LSPR of nanoantennae conveniently integrated inside a Plasmonic Vortex Lens. We show that the turning “on” or “off” of the antennae acts as a fingerprint of the OAM of the PV and we discuss a particularly meaningful case. The integrated structure is fabricated and experimentally characterized in the near field. The results are in good agreement with the simulations and seem to prove the capability to transfer OAM properties control at the nanoscale.

Tailoring the properties of an optical beam incident on a one dimensional metallic grating can attain a substantial control over the excited surface plasmon polariton wave. In this work we derive the complete analytical relations between the optical angles of incidence and the resulting surface plasmon propagation angle. These relations are demonstrated both numerically and experimentally. Following we show that there is an optimal grating that can excite any surface plasmon propagation angle between ±82.46 degrees and efficient polarization schemes which lead to negligible losses. Finally we introduce a formalism that relates general surface plasmon beams to corresponding incident optical beams and using it we demonstrate numerically a varying position surface plasmon hotspot generation.

An investigation has been performed of the low order guided modes in TiN 2D hollow metallic waveguide. The dispersion characteristics of the TiN 2D hollow metallic waveguides key guided modes are identified and analyzed. Dispersion manipulating is proposed by changing the material of the cladding region. The dispersion analysis of 2D plasmonic waveguide using TiN has been investigated for the first time and compared to that of silver. A study has been conducted on the effect of varying the material on the cutoff in the modes dispersion. The effect of changing the plasmonic material on the dispersion curve key characteristics is also identified. Finally the effect of shifting the cutoff on the enhanced transmission phenomena is investigated.

We present numerical studies, nano-fabrication and optical characterization of bowtie nanoantennas demonstrating their superior performance with respect to the electric field enhancement as compared to other Au nanoparticle shapes. For optimized parameters, we found mean intensity enhancement factors >2300x in the feed-gap of the antenna, decreasing to 1300 x when introducing a 5nm titanium adhesion layer. Using electron beam lithography we fabricated gold bowties on various substrates with feed-gaps and tip radii as small as 10 nm. In polarization resolved measurement we experimentally observed a blue shift of the surface plasmon resonance from 1.72 eV to 1.35 eV combined with a strong modification of the electric field enhancement in the feed-gap. Under excitation with a 100 fs pulsed laser source, we observed non-linear light emission arising from two-photon photoluminescence and second harmonic generation from the gold. The bowtie nanoantenna shows a high potential for outstanding conversion efficiencies and the enhancement of other optical effects which could be exploited in future nanophotonic devices.

Surface-plasmon waves have been utilized in many applications such as biological and chemical sensing and trapping, sub-wavelength optics, nonlinear optics, optical communication and more. Controlling the shape and trajectory of these waves is a key feature in enabling all of the above applications, and a challenging task. The fundamental challenges resides in the different wave properties of surface plasmon waves, with comparison to free-space waves: First, coupling a surface plasmon wave from a free-space wave requires a compensation for the missing momentum between the two wave-vectors. Second, owing to the limited propagation length of surface plasmons and the limited measurement range of their characterization tools, the resulting beams should be formed directly in the near-field. Third, unlike planar phase plates, surface plasmons are excited over a finite propagation distance and therefore their phase cannot be simply defined at a specific one-dimensional plane. Fourth, dynamic tools for controlling the wavefront of free-space beams, like spatial-light-modulators, do not exist for surface plasmons. Here we demonstrate, both numerically and experimentally, a robust holographic scheme that provides complete control over the amplitude and phase of surface-plasmons, thereby enabling the engineering of any desired plasmonic light beam. We show how all of the above challenges can be overcome by introducing a new class of binary plasmonic holograms, which are designed specifically for the near -filed. We demonstrate a large variety of plasmonic beams, such as ”self-similar”, “non-diffracting", "self-accelerating", “selfhealing”, paraxial and non-paraxial plasmonic beams, and also the dynamic generation of plasmonic bottle-beams for micromanipulation of particles.

Enhancement of localized electric field near metal (plasmonic) nanostructures can have various interesting applications in sensing, imaging, photovoltage generation etc., for which significant efforts are aimed towards developing plasmonic systems with well designed and large electromagnetic response. In this paper, we discuss the wafer scale fabrication and optical characterization of a unique three dimensional plasmonic material. The near field enhancement in the visible range of the electromagnetic spectrum obtained in these structures (order of 10⁶), is close to the fundamental limit that can be obtained in this and similar EM field enhancement schemes. The large near field enhancement has been reflected in a huge Raman signal of graphene layer in close proximity to the plasmonic system, which has been validated with FEM simulations. We have integrated graphene photodetectors with this material to obtain record photovoltage generation, with responsivity as high as A/W. As far as we know, this is the highest sensitivity obtained in any plasmonic-graphene hybrid photodetection system till date.

We review the influence of the magnetoelastic coupling with surface acoustic waves (SAWs) on the dynamic magnetic response of a periodic nanomagnet array. In addition to exciting the magnetization precession, an ultrafast laser pulse generates multiple SAW modes whose frequencies are determined by the array pitch. As a result, strong pinning of the magnetization precession frequency at the crossover points with the SAWs is observed over an extended field range. The complex spin wave spectrum can be analyzed in frequency and momentum spaces using finite element analysis emulating generation of SAWs. The magnetic response of the nanomagnets was then correctly reproduced with micromagnetic simulations taking into account additional magnetoelastic energy terms. This finding demonstrates control of the nanomagnet dynamics with the array geometry via magnetoelastic coupling, even when the magnetostatic interaction between the magnets is negligible.

The plane wave expansion (PWM) technique applied to Maxwell’s wave equations provides researchers with a supply of information regarding the optical properties of dielectric structures. The technique is well suited for structures that display a linear periodicity. When the focus is directed towards optical resonators and structures that lack linear periodicity the eigen-process can easily exceed computational resources and time constraints. In the case of dielectric structures which display cylindrical or spherical symmetry, a coordinate system specific set of basis functions have been employed to cast Maxwell’s wave equations into an eigen-matrix formulation from which the resonator states associated with the dielectric profile can be obtained. As for PWM, the inverse of the dielectric and field components are expanded in the basis functions (Fourier-Fourier-Bessel, FFB, in cylindrical and Fourier- Bessel-Legendre, BLF, in spherical) and orthogonality is employed to form the matrix expressions. The theoretical development details will be presented indicating how certain mathematical complications in the process have been overcome and how the eigen-matrix can be tuned to a specific mode type. The similarities and differences in PWM, FFB and BLF are presented. In the case of structures possessing axial cylindrical symmetry, the inclusion of the z axis component of propagation constant makes the technique applicable to photonic crystal fibers and other waveguide structures. Computational results will be presented for a number of different dielectric geometries including Bragg ring resonators, cylindrical space slot channel waveguides and bottle resonators. Steps to further enhance the computation process will be reported.

For spherically symmetric dielectric structures, a basis set composed of Bessel, Legendre and Fourier functions, BLF, are used to cast Maxwell's wave equations into an eigenvalue problem from which the localized modes can be determined. The steps leading to the eigenmatrix are reviewed and techniques used to reduce the order of matrix and tune the computations for particular mode types are detailed. The BLF basis functions are used to expand the electric and magnetic fields as well as the inverse relative dielectric profile. Similar to the common plane wave expansion technique, the BLF matrix returns the eigen-frequencies and eigenvectors, but in BLF only steady states, non-propagated, are obtained. The technique is first applied to a air filled spherical structure with perfectly conducting outer surface and then to a spherical microsphere located in air. Results are compared published values were possible.

A polarization independent band-pass filter is created by combining a silicon cross-slot waveguide and a Bragg grating cavity. By theoretically investigating different types of cavities we show how the sensitivity to polarization of the device can vary, and how we can strongly confine light in a two-dimensional slot waveguide. This kind of structure, where a slot waveguide, a photonic crystal and a nanowire waveguide are merged together, may find applications in the field of sensing. Indeed, a slight variation in the surrounding refractive index breaks the device symmetry. One polarization can thus be used to monitor the fluctuation of the other one. We describe here the principle of a Bragg grating merged with a cross slot waveguide in which a cavity is placed. We discuss the advantage of using different geometries of cavity and how this choice may affect the response of the device.

Optical biosensors present themselves as an attractive solution for integration with the ever-trending lab-on-a-chip devices. This is due to their small size, CMOS compatibility, and invariance to electromagnetic interference. Despite their many benefits, typical optical biosensors rely on evanescent field detection, where only a small portion of the light interacts with the analyte. We propose to use a silicon nanowire ridge waveguide (SNRW) for optical biosensing. This structure is comprised of an array of silicon nanowires, with the envelope of a ridge, on an insulator substrate. The SNRW maximizes the overlap between the analyte and the incident light wave by introducing voids to the otherwise bulk structure, and strengthens the contribution of the material under test to the overall modal effective index will greatly augment the sensitivity. Additionally, the SNRW provides a fabrication convenience as it covers the entire substrate, ensuring that the etching process would not damage the substrate. FDTD simulations were conducted and showed that the percentage change in the effective index due to a 1% change in the surrounding environment was more than 170 times the amount of change perceived in an evanescent detection based bulk silicon ridge waveguide.

Maxwell’s wave equations can be solved using different techniques in order to extract optical properties of a variety of dielectric structures. For structures that contain an extended axis which serve for the reference for cylindrical symmetry, we have shown that an expansion of the fields and inverse of the relative dielectric profile using a simplified and complete set of basis functions of Fourier-Bessel terms provide access to an eigenvalue formulation from which the eigen-states can be computed. We review the steps used to convert Maxwell’s equation into an eigenvalue formulation, and then proceed to discuss several applications of the technique. For cylindrically symmetric structures, the computational technique provides a significantly reduced matrix order to be populated. New target structure for the presentation consists of cylindrical space slot channel waveguide in which the channel extends in azimuthal (ϕ) direction. The channel is provided by considering the etching of external side walls of “Bragg fiber”. The configuration is similar to a structure that can support whispering-gallery modes, except that the modes highest field locations are within the ambient medium of the channel. Optical properties of this structure can be best examined through 􀜧􀯭 field component which is discontinuous by ratio of relative dielectric constants when passing air–Bragg interfaces. The ability to select Bragg dielectric properties and to introduce non-uniformities in Bragg plane spacing provides access to tuning slot channel waveguide properties and design several novel configurations.

Although it is known that the excitation of light emitters can be enhanced by surface plasmon polaritons, the corresponding rate has not yet been determined quantitatively. Here, we combine coupled mode theory and rate equation model to formulate the excitation rate in terms of measurable quantities and measure them systematically by using angle- and polarization-resolved reflectivity and photoluminescence spectroscopy. For CdSeTe quantum dots deposited on 2D Au nanohole array, we find the excitation increases by six times and the enhanced excitation rate is determined to be 8.52 meV. Our experimental results are consistent with finite-difference time-domain simulations.

Here, based on an analogy between acoustics and electromagnetism wave equations, we present an electromagnetic resonator analogous to the Helmholtz resonator in acoustics. This structure is made of a tiny slit above a box and exhibits appealing properties for applications such as thermal emission, bio-sensing or spectroscopy.

We study the dynamics of nonlinear propagation and interaction of two optical fields in arrays of dielectric subwavelength waveguides of circular cross section. Applying the finite-difference time-domain (FDTD) method, we numerically solve the Maxwell's equations considering real values for the constitutive relations. The arrays under study include a finite number of parallel waveguides with identical parameters. In our study, we focus on the light self-trapping conditions. For that, we define the properties of the incident optical fields: complex amplitude, wavelength, angle of incidence and phase difference values. As a result, we observe the strong dependence of the energy output to input critical parameters: phase difference and angle of incidence. We conclude about the possibility to generate a single output beam. The output signal position depends on the nonlinear interaction properties and is controlled by the selection of the system parameters. These results may contribute to the development of logic gates based on subwavelength waveguides.

A novel technique to fabricate metallic nanocrescents is presented. Their optical response is simulated using the finite difference time domain (FDTD) method and validated via experimental investigation and surface characterization. Nanocrescents support multiresonance extinction spectra, making them good candidates for sensing applications. In this work, silver nanocrescents are arrayed on a glass substrate. A silicon mold was used to imprint an array of polymer nanopillars that were coated using obliquely evaporated silver in order to introduce a wedge angle to the wall thickness around the pillars. The thin part of the silver wall and the inner pillars were then removed under a vertical hydrogen plasma shower and nanocrescents were formed. Scanning electron microscopy (SEM) was used to characterize the surface morphology, and the optical properties have been investigated by using spectroscopy. We then performed a FDTD analysis of the nanocrescent structures to investigate their plasmonic properties emphasizing the multiresonance behavior. A comparison between the measured and simulated extinction spectra for two different polarizations of the incident plane wave showed a slight redshift in the case of the simulated spectra in both polarization states. This slight discrepancy is attributed to the roughness of the fabricated nanostructures. The existence of multiple resonances was clearly seen in the case of measured spectra.

Hydrogen bonds and their fluctuations are one of the factors that determine the unique properties of water [1]. Building models of formation and rupture of hydrogen bonds due to non-eigen vibrations of a molecule of water is to a large extent determined by the availability of accurate information on the geometric structure of the water molecule. Geometric parameters of the water molecule have been well studied for the gaseous state. This was aided by the possibility of an experimental study of the regularities in the rotational spectra of molecules. However, some questions about the geometry of the water molecule in the liquid state remain unanswered. For example, many sources state that the valence angle of the water molecule decreases during the transition into the liquid state [2]. Based on the experimental data of molecular vibration spectra in D₂O and H₂O molecules [3], the authors have estimated valence angle of water in the liquid state. Consequently, the value of the valence angle of water in liquid state was determined to be (89 ±2)°. A question of determination of libration vibrations of water molecule, as well as the analysis of its consequent inversion doubling, based on the new information on the equilibrium angle of the water molecules in the liquid state, constitutes an interest and is discussed in the present paper.