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We study the coupling of a finite number of Bloch Surface Waves (BSWs) propagating in different directions at the surface of a dielectric multilayer. These surface waves arise from a set of diffraction orders associated to a grating on the bottom surface of the substrate that is illuminated by a normally incident beam. Simultaneous excitation of multiple BSWs is possible with a set of diffraction orders having the same radial spatial frequency. Using rigorous electromagnetic theory, we design gratings for simultaneous excitation of two, four and six BSWs propagating in directions separated by π, π/2 and π/3 azimuthal intervals, respectively.

We present an experimental realization of a novel layered metamaterial we label enhanced epsilon-near-zero (eENZ). The structure is a stack of alternating thin films made of ENZ– and dielectric material and it can be designed for desired refractive/reflective properties by appropriately tuning the film thicknesses. The structure supports thin film resonances, guided modes and Ferrel-Berreman plasmon modes and the performance of the structure shows a large improvement to many currently available bulk ENZ materials. Additionally, we recently demonstrated the possible use of eENZ for coherence switching in lasers [1]. We demonstrate the design, fabrication and characterization of the optical properties of the eENZ stack and compare the measured transmission properties with transfer matrix method (TMM) simulations.

We present optical systems, which transform isodiffracting nonstationary beams into fields obeying either cross-spectral purity or spectral invariance. The designs are hybrid refractive-diffractive imaging systems, which are able to perform the desired transformations over a broad spectral bandwidth and irrespective of the state of spatial coherence of the input beam.

Subwavelength dielectric gratings are examined in total-internal-reflection configuration. It is demonstrated experimentally that such elements, fabricated in TiO2, can perform full polarization conversion from incident TE to TM with nearly 100% efficiency. The dependence of the polarization conversion on the angle of incidence is analyzed. Rigorous diffraction theory is used to cross check the experimental results.

This paper presents a novel method to recognize inharmonic and transient bird sounds efficiently. The recognition algorithm consists of feature extraction using wavelet decomposition and recognition using either supervised or unsupervised classifier. The proposed method was tested on sounds of eight bird species of which five species have inharmonic sounds and three reference species have harmonic sounds. Inharmonic sounds are not well matched to the conventional spectral analysis methods, because the spectral domain does not include any visible trajectories that computer can track and identify. Thus, the wavelet analysis was selected due to its ability to preserve both frequency and temporal information, and its ability to analyze signals which contain discontinuities and sharp spikes. The shift invariant feature vectors calculated from the wavelet coefficients were used as inputs of two neural networks: the unsupervised self-organizing map (SOM) and the supervised multilayer perceptron (MLP). The results were encouraging: the SOM network recognized 78% and the MLP network 96% of the test sounds correctly.

Digitized wind-farm design and modeling is a demanding task in terms of the size of the data sets involved and limited computer processing power capabilities. The outcome must be as realistic as possible and show the windmills at the right scale to be an effective tool for visualization and use at presentations such as public hearings. In this paper, we present a framework for wind-farm modeling and visualization using a semi-automated approach. We divided the modeling task into subtasks and developed computer methods and algorithms to implement the subtasks. The framework uses various types of software: processing-intensive tasks are performed mostly using the MATLAB computation environment and Python scripts, the model is compiled in the Esri ArcScene environment, Autodesk 3ds Max software is used for editing three-dimensional (3D) objects, and FFmpeg software is used for compiling presentation videos from still images. The data sets employed in our approach include remotely sensed aerial images and LiDAR data, as well as 3D models of various objects such as windmills, trees, and buildings. We have modeled 11 wind-farm areas in Western Finland using the approach described in this paper. The presentation materials produced using this approach are freely available on the Internet. [ABSTRACT FROM AUTHOR]

Abstract: We investigate optical second-harmonic generation from metamaterials that consist of two-dimensional arrays of lithographically designed T-shaped gold nanodimers, where the horizontal and vertical bars of the T are separated by a nanogap. The response is shown to depend in a nontrivial way on the gap size and to exhibit an unexpected dependence on the polarizations of the fundamental and second-harmonic light. The experimental results are explained by extensive calculations of the polarized local fields at the fundamental and second-harmonic frequencies. Due to the noncentrosymmetry requirement of second-order nonlinear processes, strong local fields in the gap region alone are not sufficient to drive the response efficiently. Instead, polarization properties of the local field and its asymmetric distribution around the dimer perimeters play the key role and enable efficient interaction with the surface nonlinearity of the metal. A small slant in the relative orientations of the vertical and horizontal bars of the dimer gives rise to second-harmonic signals that are forbidden for the ideal dimer with no slant. These signals are also explained by the local-field distributions, now modified by the slant. [Copyright &y& Elsevier]