Diffraction limited photonic hook via scattering and diffraction of dual-dielectric structures

Photonic hooks have demonstrated to be great candidates for multiple applications ranging from sensing up to optical trapping. In this work, we propose a mechanism to produce such bent structured light beams by exploiting the diffraction and scattering generated by a pair of dielectric rectangles immersed in free space. It is shown how the photonic hooks are generated away from the output surface of the dielectrics by correctly engineering each individual dielectric structure to generate minimum diffraction and maximum scattering along the propagation axis. Different scenarios are studied such as dual-dielectric structures having different lateral dimensions and refractive index as well as cases when both dielectrics have the same lateral dimensions. The results are evaluated both numerically and theoretically demonstrating an excellent agreement between them. These results may open new avenues for optical trapping, focusing and sensing devices via compact and simple dual-dielectric structures.

Ranking Algorithms for Word Ordering in Surface Realization

In natural language generation, word ordering is the task of putting the words composing the output surface form in the correct grammatical order. In this paper, we propose to apply general learning-to-rank algorithms to the task of word ordering in the broader context of surface realization. The major contributions of this paper are: (i) the design of three deep neural architectures implementing pointwise, pairwise, and listwise approaches for ranking; (ii) the testing of these neural architectures on a surface realization benchmark in five natural languages belonging to different typological families. The results of our experiments show promising results, in particular highlighting the performance of the pairwise approach, paving the way for a more transparent surface realization from arbitrary tree- and graph-like structures.

Optical force acting on a particle in the presence of a backward energy flow near the focus of a gradient lens

We show that a 70-nm dielectric nanoparticle placed on the optical axis near the surface (at a distance less than 100 nm) of a high-NA gradient microlens made of silicon, which is illuminated by a laser beam of 1.55 μm wavelength, is attracted to the lens surface with a piconewton force. The profile of the lens refractive index is described by a hyperbolic secant function. If a cut-out is made in the lens output surface, then the nanoparticle will be pulled into this cut-out, producing a kind of 'optical magnet'. If a reverse energy flow is to be generated on the optical axis near the output surface of such a gradient lens, this will lead to an absorbing dielectric nanoparticle being pulled toward the surface with a greater force than a similar non-absorbing particle. In the absence of a reverse flow, both absorbing and non-absorbing particles will be attracted to the surface with an equal force. The electromagnetic fields involved are calculated using a finite difference time domain (FDTD) method and the acting forces are calculated using a Maxwell stress tensor.

Energy flux of a vortex field focused using a secant gradient lens

In this paper we simulated the focusing of left circular polarized beam with a second order phase vortex and a second-order cylindrical vector beam by a gradient index Mikaelian lens. It was shown numerically, that there is an area with a negative Poynting vector projection on Z axis, that can be called an area with backward energy flow. Using a cylindrical hole in the output surface of the lens and optimizing it one can obtain a negative flow, which will be situated in the maximum intensity region, unlike to previous papers, in which such backward energy flow regions were situated in a shadow area. Thereby, this lens will work as an “optical magnet”, it will attract Rayleigh particles (with diameter about 1/20 of the wavelength) to its surface.

Injection-Seeded Terahertz Parametric Oscillator with a Ring-Cavity Configuration

This paper reports the characteristics of an injection-seeded terahertz parametric oscillator (TPO) with a ring-cavity configuration based on the MgO:LiNbO3 crystal. The ring cavity is constituted of three mirrors and the THz wave output surface where the pump and Stokes beams are totally reflected. The THz pulse energies and the Stokes pulse energies as functions of the pump pulse energy for different seed powers of 47.5 mW, 150.7 mW, and 312.8 mW were investigated. The experimental results showed that the injection-seeded ring cavity TPO exhibited the benefits of lower pump thresholds and higher output energies for the Stokes and THz waves. The smaller the pump pulse energy, the more obvious the effect of the seed injection. The reasons for the laser performance improvement were analyzed.

Analysis of the Thermal Environment in Pedestrian Space Using 3D Thermal Imaging

Pedestrian space is an important place for people’s outdoor activities. Its thermal environment affects pedestrian walking experience, route selection and physical health. This study presents a 3D thermography-based method to analyze and evaluate the spatial distribution of thermal comfort. The proposed 3D thermal image was generated using 3D city models captured by an unmanned aerial vehicle (UAV) and thermal images gathered by an infrared camera. It can visualize construction elements, but also simply output surface temperatures at selected points. This paper described the process of using 3D thermal images to analyze the built environment, and selected two pedestrian spaces as case study objects. Their thermal images and mean radiant temperatures (MRT) were obtained from field measurement data collected by a drone and infrared camera. The following findings were obtained: (a) the MRT difference in the pedestrian space between sunlit and shaded areas was more than 3 °C; (b) the MRT values at the measurement points near vegetation were lower; (c) when the ratio of street height to width (H/W) was larger, the MRT values at all measurement points varied slightly. These findings can be used for the designers to evaluate and improve the thermal environment in pedestrian space.

Focusing a second-order cylindrical vector beam with a gradient index Mikaelian lens

In this paper, we numerically simulate the focusing of a second-order cylindrical vector beam with a gradient index Mikaelian lens. It is shown that the lens forms a region of the reverse energy flow near its output surface. If the lens has an on-axis micropit, the region of the direct energy flow can be confined within the lens material, whereas that of the reverse energy flow is put out in free space.

Hybrid Neuro-Fuzzy Classification Algorithm for Social Network

People tend to build and maintain their friendship relying on SNS nowadays. Thus, the problem of how to organize the social network accurately and automatically. In this paper, a hybrid neuro-fuzzy approach is used. . Many aspect impact the error values like input/output, membership functions, the training data arrays, and the number of epochs needed to train the model. This paper is based on hybrid Neuro-Fuzzy concept for testing the link prediction for facebook data. We use Matlab to calculate average testing Error, View Generation Rule, Output Surface.