Rotatum of Light

Vortices are ubiquitous in nature and can be observed in fluids, condensed matter, and even in the formation of galaxies. Light, too, can evolve like a vortex. Optical vortices are exploited in light-matter interaction, free-space communications, and imaging. Here, we introduce optical rotatum; a new degree-of-freedom of light in which an optical vortex experiences a quadratic chirp in its orbital angular momentum along the optical path. We show that such an adiabatic deformation of topology is associated with the accumulation of a Berry phase factor which in turn perturbs the propagation constant (spatial frequency) of the beam. Remarkably, the spatial structure of optical rotatum follows a logarithmic spiral; a signature that is commonly seen in the pattern formation of seashells and galaxies. Our work expands previous literature on structured light, offers new modalities for light-matter interaction, communications, and sensing, and hints to analogous effects in condensed matter physics and Bose-Einstein condensates.Comment: 24 Pages, 4 Main Figures, 2 Extended Figure

Experimental Demonstration Of Attenuation Resistant Frozen Waves

We present an experimental demonstration of a class of beams, namely Frozen Waves, that can carry predetermined longitudinal intensity profiles in the presence of modeled loss. These waveforms consist of a superposition of equal frequency Bessel beams with different transverse and longitudinal wavenumbers, and are generated using a programmable spatial light modulator addressed by computer-generated hologram. Attenuation-resistant Frozen Waves can address challenges associated with light-matter interaction in absorbing media encountered in imaging, remote sensing, and particle micro-manipulation, to name a few.9893Conference on Laser Sources and Applications IIIAPR 04-05, 2016Brussels, BELGIU

Modeling and Control PV-Wind Hybrid System Based On Fuzzy Logic Control Technique

As energy demands around the world increase, the need for a renewable energy sources that will not harm the environment is increased. The overall objective of renewable energy systems is to obtain electricity with competitive cost and even benefit with respect to other energy sources. The optimal design of renewable energy system can significantly improve the economical and technical performance of power supply. This paper presents the power management control using fuzzy logic control technique. Also, a complete mathematical modeling and MATLAB/Simulink model for the proposed the electrical part of an aquaculture system is implemented to track the system performance. The simulation results show the feasibility of control technique

A New Control and Design of PEM Fuel Cell Powered Air Diffused Aeration System

Aeration of water by using PEM fuel cell power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. This paper presents a new design and control of PEM fuel cell powered by diffused air aeration system for a shrimp farm in Mersa Matruh in Egypt. Also Artificial intelligence (AI) techniques control is used to control the fuel cell output power by controlling input gases flow rate. Moreover the mathematical modeling and simulation of PEM fuel cell is introduced. A comparison study is applied between the performance of fuzzy logic control (FLC) and neural network control (NNC). The results show the effectiveness of NNC over FLC

Introducing Berry phase gradients along the optical path via propagation-dependent polarization transformations

Abstract As a classical or quantum system undergoes a cyclic evolution governed by slow change in its parameter space, it acquires a topological phase factor known as the geometric or Berry phase. One popular manifestation of this phenomenon is the Gouy phase which arises when the radius of curvature of the wavefront changes adiabatically in a cyclic manner, for e.g., when focused by a lens. Here, we report on a new manifestation of the Berry phase in 3D structured light which arises when its polarization state adiabatically evolves along the optical path. We show that such a peculiar evolution of angular momentum, which occurs under free space propagation, is accompanied by an accumulated phase shift that elegantly coincides with Berry's prediction. Unlike the conventional dynamic phase, which accumulates monotonically with propagation, the Berry phase observed here can be engineered on demand, thereby enabling new possibilities; such as spin-dependent spatial frequency shifts, and modified phase matching in resonators and nonlinear interactions. Our findings expand the laws of wave propagation and can be applied in optics and beyond

Do bilayer metasurfaces behave as a stack of decoupled single-layer metasurfaces?

Flat optics or metasurfaces have opened new frontiers in wavefront shaping and its applications. Polarization optics is one prominent area which has greatly benefited from the shape-birefringence of metasurfaces. However, flat optics comprising a single layer of meta-atoms can only perform a subset of polarization transformations, constrained by a symmetric Jones matrix. This limitation can be tackled using metasurfaces composed of bilayer meta-atoms but exhausting all possible combinations of geometries to build a bilayer metasurface library is a very daunting task. Consequently, bilayer metasurfaces have been widely treated as a cascade (product) of two decoupled single-layer metasurfaces. Here, we test the validity of this assumption by considering a metasurface made of TiO2 on fused silica substrate at a design wavelength of 532 nm. We explore regions in the design space where the coupling between the top and bottom layers can be neglected, i.e., producing a far-field response which approximates that of two decoupled single-layer metasurfaces. We complement this picture with the near-field analysis to explore the underlying physics in regions where both layers are strongly coupled. Our analysis is general and it allows the designer to efficiently build a multi-layer metasurface, either in transmission or reflection, by only running one full-wave simulation for a single-layer metasurface.Comment: 26 pages, 12 figure

Point singularity array with metasurfaces

Phase singularities are loci of darkness surrounded by monochromatic light in a scalar field, with applications in optical trapping, super-resolution imaging, and structured light-matter interactions. Although 1D singular structures, such as optical vortices, are the most common due to their robust topological properties, uncommon 0D (point) and 2D (sheet) singular structures can be generated by wavefront-shaping devices such as metasurfaces. Here, using the design flexibility of metasurfaces, we deterministically position ten identical point singularities in a cylindrically symmetric field generated by a single illumination source. The phasefront is inverse-designed using phase gradient maximization with an automatically-differentiable propagator. This process produces tight longitudinal intensity confinement. The singularity array is experimentally realized with a 1 mm diameter TiO2 metasurface. One possible application is blue-detuned neutral atom trap arrays, for which this light field would enforce 3D confinement and a potential depth around 0.22 mK per watt of incident trapping laser power. Metasurface-enabled point singularity engineering may significantly simplify and miniaturize the optical architecture required to produce super-resolution microscopes and dark traps