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Subwavelength resonant lattices offer a wide range of fascinating spectral phenomena under broadside illumination. The resonance mechanism relies on the generation of lateral Bloch modes that are phase matched to evanescent diffraction orders. The spectral properties and the total number of resonance states are governed by the structure of leaky modes and the mode count. This study investigates the effect of interface modifications on the band dynamics and bound-state transitions in guided-mode resonant lattices. We provide photonic lattices comprising rectangular Si3N4 rods with a liquid film with an adjustable boundary. The band structures and band flips are examined through numerical simulations using the rigorous coupled-wave analysis (RCWA) method and analyzing the zero-order spectral reflectance as a function of the incident angle. The band structures and band flips are examined through numerical simulations, and the influences of the refractive index and the thickness of the oil layer on the band dynamics are investigated. The results reveal distinct resonance linewidths corresponding to different refractive indices of the oil layer. Furthermore, the effect of the oil thickness on the band dynamics is explored, demonstrating precise control over the number of propagating modes within the lattice structure. Theoretical simulations and experimental results are presented for a subwavelength silicon-nitride lattice combined with a liquid film featuring an adjustable boundary. The presence of a relatively thick liquid waveguiding region enables the emergence of additional modes, including the first four transverse-electric (TE) leaky modes, which produce observable resonance signatures. Through experimental manipulation of the basic lattice's duty cycle, the four bands undergo quantifiable band transitions and closures. The experimental results obtained within the 1400–1600 nm spectral range exhibit reasonable agreement with the numerical analysis. These findings underscore the significant role played by the interface in shaping the band dynamics of the lattice structure, providing valuable insights into the design and optimization of photonic lattices with adjustable interfaces. [ABSTRACT FROM AUTHOR]

The properties of topological edge states of resonant photonic lattices are reported. The canonical 1D lattice embodies all chief qualities necessary for a complete comprehension of the variety of fundamental physical processes at play. Radiating topological edge states are understood in terms of leaky‐mode resonance stimulated by counter‐propagating Bloch modes. As a free‐space electromagnetic wave illuminates the junction between band‐flipped photonic lattices, quasi‐leaky resonant light is localized at the interface, which embodies the characteristics of the closed‐band state of the composite lattice. Rigorous numerical examples with Ge/ZnSe‐based lattices with a finite number of periods and having homogeneous sublayers illustrate the resonance properties of the constituent lattices, the band‐closed lattice, and the composite lattice hosting the radiant edge state. The topological interface is seen to radiate effectively near the wavelength where the band closes. With the insight gained from the 1D analysis, a representative 2D lattice is similarly treated. As orthogonal leaky modes are supported by 2D lattices, the interface‐bound energy flow picture is more intriguing. Thus, lateral TE and TM modes can be excited to run along the topological interface or normal to it. Versatile power flow, energy density, and radiation characteristics are then available at the 2D topological interface. [ABSTRACT FROM AUTHOR]

We treat fundamental resonance effects in hybridized metal-dielectric elements that may find applications in absorption, sensing, and displays. The hybrid structures support guided-mode resonance (GMR) and surface plasmon resonance (SPR) operating independently or in unison. Numerical simulations of periodic resonant films coated in gold that effectively combine principles of both resonance effects show viability of absorbers with equalized spectra and hybrid waveguides. The experimentally measured spectra show qualitative agreement with theoretical models. We introduce a hybrid GMR/SPR refractive-index sensor consisting of a thin aluminum film integrated with a subwavelength silicon-dioxide grating. The sensor operates between the Rayleigh wavelengths of the cover and the substrate. A GMR is excited by TE-polarized light and is subsequently attenuated by the Rayleigh anomaly as the cover index increases. In transverse-magnetic-polarized light, it operates as a Rayleigh sensor with sharp spectral features that would be easily monitored with a spectrum analyzer. As a final device example, we present simulation results pertaining to a one-dimensional color filter utilizing SPR, GMR, and the Rayleigh anomaly and convert it into a polarization insensitive two-dimensional device. With dual periods along orthogonal directions, two resonant peaks are induced within the visible spectrum for unpolarized input light rendering a colormixing effect. The output color of the dual pixel is tunable with the input polarization state. [ABSTRACT FROM AUTHOR]

Discusses Canada's policy of supporting the Kyoto Protocol in its current form. Highlights of the Kyoto Protocol; Technical problems and concerns on emission trading program; Danger for Canada of combining international emission trading and foreign business ownership; Negative economic implications of the protocol trading provisions.

In this paper, a frequency-selective structure based on guided-mode resonance effects in all-dielectric waveguide gratings is demonstrated theoretically and verified experimentally. Reflection (band-stop) filters with high efficiency, extended low-sideband reflection, and symmetric line shapes are designed by embedding gratings in layered antireflection structures. Reflection filter examples employing common dielectric materials illustrate linewidth control by grating modulation. An additional mechanism for linewidth control is demonstrated with phase-shifted gratings. Double-line reflection filters are obtained in structures containing two gratings with different grating periods. High-efficiency transmission (bandpass) filters are demonstrated using multilayer waveguide gratings in a high-reflectance thin-film configuration with a single grating in the center layer bordered by dielectric mirrors composed of high/low quarter-wave layers. Single-layer and multilayer waveguide gratings operating as reflection and transmission filters, respectively, were built and tested in the 4-20-GHz frequency range. The presence of guided-mode resonance notches and peaks is clearly established by the experimental results, and their spectral location and line shape is found to be in excellent agreement with the theoretical predictions [ABSTRACT FROM PUBLISHER]

The Stockholm bypass (E4 Förbifart Stockholm) is being built by the Swedish Transport Administration (Trafikverket) – the office responsible for transport infrastructure in Sweden. The project aims to improve connections between the regional town centres and reduce congestion on the main urban roads. The route, which runs mainly underground, employs numerous contractors and has a planned construction period of 14 years, preceded by a 10‐year planning phase. This article looks at three projects: the FSE 61 Akalla Interchange, the FSE 309 Lovön Interchange and in particular, the FSE 613 Akalla Tunnel. The Akalla Tunnel is driven as a conventional full‐face excavation with pre‐grouting and supported with rock bolts and steel‐fibre‐reinforced shotcrete. The tunnel excavation is followed by the interior work comprising precast concrete walls, a suspended membrane reinforced with shotcrete, ceiling foundations and the carriageway structure. [ABSTRACT FROM AUTHOR]

Properties of photonic devices fashioned with dual‐grating metamaterials are reported. Enclosed by dual periodic regions, laterally propagating Bloch modes undergo radiative scattering and leaky‐mode resonance whose properties differ markedly from those with single periodicity. The resonance signatures are sensitively controlled by the relative parameters of the periodic regions. In particular, if they are physically identical and separated by a half‐wavelength, there ensues a bound state in the continuum (BIC) with extremely narrow resonance linewidth. On varying the separation between the periodic layers, the linewidth and corresponding Q can be tuned. This is confirmed experimentally via nanoimprinted dual‐grating membranes. The experimental spectra agree well with rigorously computed spectra as well with an analytical model due to Avrutsky. At grating‐depth and thickness values satisfying this model, three different types of BICs are supported by a single metamembrane. Two BICs appear at normal incidence at the Γ point with one being a quasi‐BIC on one band edge while a true symmetry‐protected BIC resides on the other edge. Moreover, a quasi‐BIC state away from the Γ point in the same device is demonstrated. Whereas these results are based on a simple model with 1D periodicity, the primary properties will carry over to general 2D/3D photonic lattices. [ABSTRACT FROM AUTHOR]

2D resonant gratings enable dual angular tunability by controlling the plane of incidence (POI) under linear polarization. If the POI is set to be perpendicular to the electric field vector (s‐polarization or transverse electric (TE) polarization), an excited TE mode provides spectral tuning. The orthogonally propagating transverse magnetic (TM) mode is robust in angle. Conversely, if the POI is set for p‐polarization, an excited TM mode provides the tuning. Detailed explanations of the underlying physical processes are set forth by decomposing the 2D lattice into equivalent 1D gratings using second‐order effective‐medium theory. This is shown to work extremely well even for a strongly modulated lattice with refractive‐index contrast of 3. With proper design and corresponding experiments, a widely tunable notch filter covering long‐wave infrared bands is demonstrated. Experimentally varying the incidence angle up to 16° under p‐polarization, a notch channel in TM mode tunes across a band exceeding 0.5 µm with the TE channel remaining at a constant wavelength. The interesting appearance of a resonance channel originating in diagonally propagating leaky modes is briefly examined. The analysis and experiments presented can be useful for realizing diverse 2D tunable filters while furnishing methodology for detailed understanding of the attendant near fields and mode structure. [ABSTRACT FROM AUTHOR]

Photonic multiline filters exhibiting periodic resonance lines on a dense spectral grid in a broad wavelength range are demonstrated. We design the filters using rigorous numerical methods and then proceed with experimental verification by patterning, etching, and collecting spectral data. We use standard double-side-polished 300-µm-thick silicon wafers for the experiments. On one side of the wafer, we place a shallow grating whereas the other side has a quarter-wave antireflection layer. An example filter with a ~200-nm-deep TiO2 grating on the wafer yields 12 narrow resonance peaks within a 10-nm wavelength range centered at 1550 nm. The spectral width of each filter peak is ~0.1 nm with a free spectral range of ~0.8 nm. Peak efficiency approaches 80% with low sidebands between the resonant filter lines. We discuss briefly design of polarization-independent periodic filters and the concept of Brewster-angle filters. Possible applications include spectral sam. pling and wavelength discretization as used, e.g., in sensing gas species and quantifying toxic gas concentrations. [ABSTRACT FROM AUTHOR]

We propose a mechanism of ultrahigh-Q metallic nanocavity resonances that involves an efficient loss-compensation scheme favorable for room-temperature operation. We theoretically show that surface plasmon-polaritons excited on the entrance and exit interfaces of a metallic nanocavity array efficiently transfer external optical gain to the cavity modes by inducing resonantly-amplified intracavity feedback. Surprisingly, the modal gain in the nanocavity with the externally amplified feedback is inversely proportional to the cavity length as opposed to conventional optical cavity amplifiers requiring longer cavities for higher optical gain. Utilizing this effect, we numerically demonstrate room-temperature nanocavity resonance Q-factor exceeding 104 in a 25-nm-wide silver nanoslit array. The proposed mechanism provides a highly efficient plasmonic amplification process particularly for subwavelength plasmonic cavities which are essential components in active nanoplasmonic devices. [ABSTRACT FROM AUTHOR]

Abstract: Rapid thermal annealing is applied to induce crystallization of sputtered amorphous silicon deposited on thermally grown oxide layers. The influence of annealing temperatures in the range of 600°C–980°C is systematically investigated. Using scanning-electron microscopy, ellipsometry and X-ray diffraction techniques, the structural and optical properties of the films are determined. An order-of-magnitude reduction of the extinction coefficient is achieved. We show that the optical constants can be tuned for different design requirements by controlling the process parameters. For example, we obtain a refractive index of ~3.66 and an extinction coefficient of ~0.0012 at the 1550-nm wavelength as suitable for a particular optical filter application where a high refractive index and low extinction coefficient is desired. [Copyright &y& Elsevier]

We treat wideband subwavelength guided-mode resonant gratings with grating-depth dependent duty cycles. By rigorous numerical computations, we visualize Bloch modal evolution while transforming the grating profile from trapezoid to triangle. Parametric optimization is achieved using the coordinate transformation method of Chandezon. With the increase of the profile base angle, the higher mixed resonant modes TM1 , 1 & 2 attract and combine and interact with the modes at both sides, forming wide reflection bands. This modal combination and interaction are the key determinant of broadband reflectivity spectral location and width. The optimized structure exhibits 99% reflectivity across a 613-nm spectral range, spanning a 1438- to 2051-nm wavelength range with a fractional bandwidth of ∼35 %. It is shown that gratings with trapezoidal profiles possess a good tolerance to groove depth variation, thus being easier to fabricate with a diamond-tip than triangular profile-based gratings. [ABSTRACT FROM AUTHOR]

We demonstrate a long-range surface plasmon-polaritons (LRSPP) refractive-index sensor using an asymmetric double-electrode LRSPP waveguide configuration. The LRSPP sensor is inherently self-referencing by virtue of two Bragg wavelengths in the transmission spectrum generated by a Bragg grating. The measured sensitivity is about 130 nm/RIU and 27 pm/K, which means a sensing resolution of ∼10-6 RIU and a temperature determination with an inaccuracy of 0.04 K under measurement accuracy of the Bragg wavelength of 1 pm. The sensor dimensions of 1.95 mm in total length and submicrometer in fluidic-channel thickness may be desirable for highly integrated sensors based on LRSPP. [ABSTRACT FROM AUTHOR]

Background. The injured anterior cruciate ligament (ACL) has a limited healing capacity leading to persisting instability. Hypothesis/Purpose. To study if the application of a brace, producing a dynamic posterior drawer force, after acute ACL injury reduces initial instability. Study Design. Cohort study. Methods. Patients treated with the ACL-Jack brace were compared to controls treated with primary ACL reconstruction und controls treated nonsurgically with functional rehabilitation. Measurements included anterior laxity (Rolimeter), clinical scores (Lysholm, Tegner, and IKDC), and MRI evaluation. Patients were followed up to 24 months. Results. Patients treated with the ACL-Jack brace showed a significant improvement of anterior knee laxity comparable to patients treated with ACL reconstruction, whereas laxity persisted after nonsurgical functional rehabilitation. The failure risk (secondary reconstruction necessary) of the ACL-Jack group was however 21% (18 of 86) within 24 months. Clinical scores were similar in all treatment groups. Conclusion. Treatment of acute ACL tears with the ACL-Jack brace leads to improved anterior knee laxity compared to nonsurgical treatment with functional rehabilitation. [ABSTRACT FROM AUTHOR]

Metal-catalysed etching (MCE) is a simple and versatile method for fabrication of silicon nanowires, of high structural quality. When combined with laser interference lithography (LIL), large areas of periodic structures can be generated in only few steps. The aspect ratio of such periodic structure is however commonly not higher than several decades or very few hundred. Here, a combined MCE and LIL techniques were applied to fabricate dense (4 × 10 cm), periodic arrays of vertically aligned silicon nanowires with aspect ratio of up to 10. This is a considerable higher number than previously reported on for periodic silicon wire arrays prepared with top-down approaches. The wires were slightly tapered, with top and bottom diameters ranging from 370 to 195 nm and length of up to 200 μm. A potential use of the nanowires as light absorber is demonstrated by measuring reflection in integrating sphere. An average total absorption of ~97 % was observed for 200-μm-long wires in the spectral range of 450-1000 nm. A comparison to simulated absorption spectra is given. [ABSTRACT FROM AUTHOR]

Photonic resonance in lossy films with 1D periodicity is generally associated with narrow spectral, angular, and polarization‐selective absorption. Contrarily, in this paper a 1D amorphous Si grating structure is demonstrated that efficiently absorbs fully hemispherical unpolarized light in the entire visible spectral domain. The absorber provides a broad spectral continuum of densely populated resonant photonic states as well as a cooperating wide‐angular antireflection effect, resulting in the observed broadband, omnidirectional, and polarization‐insensitive light absorption. The absorber performance is experimentally verified with precise fabrication and conical input beam spectral analysis. The absorber's fundamental mechanisms, explained in detail, are applicable to other semiconducting materials including GaAs, Ge, and SiC. These materials provide the absorber design with potential impact on practical device applications including near/mid/long infrared detectors and stray background rejection surfaces for imaging and spectroscopy. [ABSTRACT FROM AUTHOR]

We propose a semiconductor metasurface that simultaneously performs two independent functions: focusing and polarization filtering. The wavefronts of the reflected and transmitted light distributions are precisely manipulated by spatial parametric variation of a subwavelength thin-film Si grating, which inherently possesses polarization filtering properties. We design a 12-μm-wide metasurface containing only nineteen Si grating ridges. Under a 10-μm-wide unpolarized Gaussian beam incidence at wavelength of 1.55 μm, the resulting device shows promising theoretical performance with high power efficiency exceeding 80% and polarization extinction ratio of ~10 dB with focal spot diameters near 1-2 μm. [ABSTRACT FROM AUTHOR]

We present spectral and angular transmission filters based on the guided-mode resonance (GMR) effect cooperating with the Rayleigh anomaly in a subwavelength nanograting. We theoretically and experimentally show that the onset of higher diffraction orders at the Rayleigh anomaly dramatically sharpens a GMR transmission peak in both spectral and angular domains. This unique transmission spectrum is tightly delimited in angle and wavelength as experimentally demonstrated with a precisely fabricated device. [ABSTRACT FROM AUTHOR]

We demonstrate the plasmonic analogue of a coherent photonic effect known as coherent perfect absorption. A periodically nanopatterned metal film perfectly absorbs multiple coherent light beams coupling to a single surface plasmon mode. The perfect absorbing state can be switched to a nearly perfect scattering state by tuning the phase difference between the incident beams. We theoretically explain the plasmonic coherent perfect absorption by considering time-reversal symmetry of surface plasmon amplification by stimulated emission of radiation. We experimentally demonstrate coherent control of the plasmonic absorption in good agreement with a coupled-mode theory of dissipative resonances. Associated potential applications include absorption-based plasmonic switches, modulators, and light-electricity transducers. [ABSTRACT FROM AUTHOR]

A facile procedure to fabricate large arrays of highly ordered metal nanocups, 250 nm in diameter, is reported. The nanostructure is generated from periodic photoresist templates created by holographic laser interference lithography. A subsequent gold deposition and a peeling-off step respectively results in a large area of hemispherical nano-indentations or nanocups. A wide range of coating materials can be used, and the dimensions and periodicity of the structure are easily controlled. The structure's ability to support localized surface plasmon polaritons was manifested by reflectance spectroscopy. A good correlation between experimental data and calculated data was observed. [ABSTRACT FROM AUTHOR]

We present the design, fabrication, and characterization of a guided-mode resonance polarizer operating in the telecommunication band. This polarizer consists of a single one-dimensional silicon grating layer and a glass substrate. The device is designed using inverse mathematical methods and fabricated by thin-film deposition, holographic-interference patterning, and etching. The fabricated polarizer has high transmittance for transverse-magnetic polarization and low transmittance for transverse-electric polarization over a ∼200 nm wavelength range. Its experimental extinction ratio is ∼670:1 at a central wavelength λc=1563 nm. Experimental and theoretical results are in good agreement. [ABSTRACT FROM AUTHOR]

Assessing levels of neuropeptide Y (NPY) in the human body has many medical uses. Accordingly, we report the quantitative detection of NPY biomarkers applying guided-mode resonance (GMR) biosensor methodology. The label-free sensor operates in the near-infrared spectral region exhibiting distinctive resonance signatures. The interaction of NPY with bioselective molecules on the sensor surface causes spectral shifts that directly identify the binding event without additional processing. In the experiments described here, NPY antibodies are attached to the sensor surface to impart specificity during operation. For the low concentrations of NPY of interest, we apply a sandwich NPY assay in which the sensor-linked anti-NPY molecule binds with NPY that subsequently binds with anti-NPY to close the sandwich. The sandwich assay achieves a detection limit of ~0.1 pM NPY. The photonic sensor methodology applied here enables expeditious high-throughput data acquisition with high sensitivity and specificity. The entire bioreaction is recorded as a function of time, in contrast to label-based methods with single-point detection. The convenient methodology and results reported are significant, as the NPY detection range of 0.1–10 pM demonstrated is useful in important medical circumstances. [ABSTRACT FROM AUTHOR]

Fabrication and sensor application of a simple plasmonic structure is described in this paper. The sensor element consists of nano-patterned gold film brought about from two-dimensional periodic photoresist templates created by holographic laser interference lithography. Reflectance spectroscopy revealed that the sensor exhibits significant refractive index sensitivity. A linear relationship between shifts in plasmonic resonances and changes in the refractive index were demonstrated. The sensor has a bulk sensitivity (SB) of 880 nm/refractive index unit and work under normal incidence conditions. This sensitivity exceeded that of many common types of plasmonic sensors with more intricate structures. A modeled spectral response was used to study the effect of its geometrical dimensions on plasmonic behavior. A qualitative agreement between the experimental spectra and modeled ones was obtained. [ABSTRACT FROM AUTHOR]

We propose a free-space electro-optic transmission modulator based on multiple p-n-junction semiconductor subwavelength gratings. The proposed device operates with a high-Q guided-mode resonance undergoing electro-optic resonance shift due to direct electrical control. Using rigorous electrical and optical modeling methods, we theoretically demonstrate a modulation depth of 84%, on-state efficiency 85%, and on-off extinction ratio of 19 dB at 1,550 nm wavelength under electrical control signals within a favorably low bias voltage range from −4 V to +1 V. This functionality operates in the transmission mode and sustainable in the high-speed operation regime up to a 10-GHz-scale modulation bandwidth in principle. The theoretical performance prediction is remarkably advantageous over plasmonic tunable metasurfaces in the power-efficiency and absolute modulation-depth aspects. Therefore, further experimental study is of great interest for creating practical-level metasurface components in various application areas. [ABSTRACT FROM AUTHOR]