scholarly journals Bifunctional Metamaterials Using Spatial Phase Gradient Architectures: Generalized Reflection and Refraction Considerations

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2201
Author(s):  
Octavian Danila ◽  
Doina Manaila-Maximean
Keyword(s):  
Wave Front ◽  
Negative Refraction ◽  
Phase Distribution ◽  
Normal Incidence ◽  
Polarization Measurement ◽  
Phase Gradient ◽  
Spatial Phase ◽  
Spatially Resolved ◽  
Reflection And Refraction ◽  
Polarization Converters

We report the possibility of achieving normal-incidence transmission at non-normal incidence angles using thin interfaces made of metasurface structures with an appropriately-designed positive spatial phase distributions. The reported effect represents a consequence of generalized reflection and refraction, which, although having been studied for discovering exotic effects such as negative refraction, to the best of our knowledge fails to address normal incidence conditions in positive phase distribution and its underlying consequences. Normal-incidence conditions can be angle-tuned by modifying the vales of the phase distribution gradients. Furthermore, for configurations around the normal-incidence angles, the metasurface will exhibit a bifunctional behavior—either divergent or convergent. All these properties are essential for applications such as optical guiding in integrated optics, wave front sensing devices, polarization controllers, wave front-to-polarization converters, holographic sensors, and spatially-resolved polarization measurement.

Broadband Optical Negative Refraction Based on Dielectric Phase Gradient Metagratings

2021 ◽  
Author(s):  
Qiannan Wu ◽  
HaoHao Chen ◽  
YanYan Cao ◽  
Shan Zhu ◽  
Baoyin Sun ◽  
...  
Keyword(s):  
Negative Refraction ◽  
Phase Gradient ◽  
Dielectric Phase

scholarly journals An organic crystalline state in ageing atmospheric aerosol proxies: spatially resolved structural changes in levitated fatty acid particles

2021 ◽  
Author(s):  
Adam Milsom ◽  
Adam M. Squires ◽  
Jacob A. Boswell ◽  
Nicholas J. Terrill ◽  
Andrew D. Ward ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Air Quality ◽  
Liquid Crystalline ◽  
Structural Changes ◽  
Unsaturated Fatty Acids ◽  
Organic Aerosols ◽  
Cloud Formation ◽  
Phase Gradient ◽  
Spatially Resolved ◽  
Surface Active

Abstract. Organic aerosols are key components of the Earth’s atmospheric system. The phase state of organic aerosols is known to be a significant factor in determining aerosol reactivity, water uptake and atmospheric lifetime – with wide implications for cloud formation, climate, air quality and human health. Unsaturated fatty acids contribute to urban cooking emissions and sea spray aerosols. These compounds, exemplified by oleic acid and its sodium salt, are surface active and have been shown to self-assemble into a variety of liquid-crystalline phases upon addition of water. Here we observe a crystalline acid–soap complex in acoustically levitated oleic acid–sodium oleate particles. We developed a synchrotron-based simultaneous Small-Angle & Wide-Angle X-ray Scattering (SAXS/WAXS)/Raman microscopy system to probe physical and chemical changes in the proxy during exposure to humidity and the atmospheric oxidant ozone. We present a spatially resolved structural picture of a levitated particle during humidification, revealing a phase gradient consisting of a disordered liquid crystalline shell and crystalline core. Ozonolysis is significantly slower in the crystalline phase compared with the liquid phase and a significant portion (34 ± 8 %) of unreacted material remains after extensive oxidation. We present experimental evidence of inert surface layer formation during ozonolysis, taking advantage of spatially resolved simultaneous SAXS/WAXS experiments. These observations suggest atmospheric lifetimes of surface-active organic species in aerosols are highly phase dependent, potentially impacting on climate, urban air quality and long-range transport of pollutants such as Polycyclic Aromatic Hydrocarbons (PAHs).

Statistical properties of spatial phase distribution in developed speckle field

1993 ◽  
Author(s):  
Boris B. Gorbatenko ◽  
Igor S. Klimenko ◽  
Ludmila A. Maksimova ◽  
Vladimir P. Ryabukho
Keyword(s):  
Phase Distribution ◽  
Statistical Properties ◽  
Speckle Field ◽  
Spatial Phase

Spatial phase retrieval of vortex beam using convolutional neural network

2021 ◽  
Author(s):  
Ge Ding ◽  
Wenjie Xiong ◽  
Peipei Wang ◽  
Zebin Huang ◽  
Yanliang He ◽  
...  
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Phase Retrieval ◽  
Phase Distribution ◽  
Spherical Wave ◽  
Vortex Beam ◽  
Phase Front ◽  
Free Space Optical ◽  
Practical Applications ◽  
Spatial Phase

Abstract Vortex beam (VB) possessing spatially helical phase–front has attracted widespread attention in free-space optical communication, etc. However, the spiral phase of VB is susceptible to atmospheric turbulence, and effective retrieval of the distorted conjugate phase is crucial for its practical applications. Herein, a convolutional neural network (CNN) approach to retrieve the phase distribution of VB is experimentally demonstrated. We adopt a spherical wave to interfere with VB for converting its phase information into intensity changes, and construct a CNN model with excellent image processing capabilities to directly extract phase–front features from the interferogram. Since the interference intensity is correlated with the phase–front, the CNN model can effectively reconstruct the wavefront of conjugate VB carrying different initial phases from a single interferogram. The results show that the CNN-based phase retrieval method has a loss of 0.1418 in the simulation and a loss of 0.2344 for the experimental data, and remains robust even in turbulence environments. This approach can improve the information acquisition capability for recovering the distorted wavefront and reducing the reliance on traditional inverse retrieval algorithms, which may provide a promising tool to retrieve the spatial phase distributions of VBs.

scholarly journals Shifting beams at normal incidence via controlling momentum-space geometric phases

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jiajun Wang ◽  
Maoxiong Zhao ◽  
Wenzhe Liu ◽  
Fang Guan ◽  
Xiaohan Liu ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Momentum Space ◽  
Geometric Phase ◽  
Phase Distribution ◽  
Periodic Structures ◽  
Incident Beam ◽  
Normal Incidence ◽  
Large Shift ◽  
Practical Applications ◽  
Photonic Crystal Slab

AbstractWhen hitting interfaces between two different media, light beams may undergo small shifts. Such beam shifts cannot be described by the geometrical optics based on Snell’s law and their underlying physics has attracted much attention. Conventional beam shifts like Goos-Hänchen shifts and Imbert-Fedorov shifts not only require obliquely incident beams but also are mostly very small compared to the wavelength and waist size of the beams. Here we propose a method to realize large and controllable polarization-dependent lateral shifts for normally incident beams with photonic crystal slabs. As a proof of the concept, we engineer the momentum-space geometric phase distribution of a normally incident beam by controlling its interaction with a photonic crystal slab whose momentum-space polarization structure is designed on purpose. The engineered geometric phase distribution is designed to result in a large shift of the beam. We fabricate the designed photonic crystal slab and directly observe the beam shift, which is ~5 times the wavelength and approaches the waist radius. Based on periodic structures and only requiring simple manipulation of symmetry, our proposed method is an important step towards practical applications of beam shifting effects.

scholarly journals Vertical distribution of brine and volume structure thin one year ice Amur bay on base NMR and MRT dates

2019 ◽  
Vol 59 (5) ◽  
pp. 859-869
Author(s):  
N. A. Mel’nichenko ◽  
A. V. Tyuveev ◽  
A. Yu. Lazaryuk ◽  
V. E. Savchenko ◽  
E. V. Kustova
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Air Temperature ◽  
Phase Distribution ◽  
Solid Phase ◽  
Empirical Relation ◽  
Amur Bay ◽  
Spatial Phase ◽  
Arctic Ice ◽  
One Year

It was studying distribution of liquid and solid phases in pores one year sea ice on Amur Bay with using NMR and MRT methods in period 20132016. According to findings predominant factor in ice structure formation is snow cover. The patterns of brine content and solid phase distribution are considered in interdependence with air temperature and corresponding ice layer temperatures in compliance with preceding weather conditions. Differences in vertical profiles for temperature and salinity for winter and spring periods was marked. The main features of spatial phase dictribution in thin ice in comparision Arctic ice are presented. Just snow cover effects on ice parameters was demonstrated using data 20132016. The relationship of interlayings number in ice with its thickness, air temperature, and snow cover thickness is discussed. The main features of spatial phase dictribution in thin ice in comparision Arctic ice are presented. The empirical relation for calculations thin sea ice thickness was suggested.

Sign in / Sign up

Export Citation Format

Share Document