162 research outputs found
Engineered Optical Nonlocality in Nanostructured Metamaterials
We analyze dispersion properties of metal-dielectric nanostructured
metamaterials. We demonstrate that, in a sharp contrast to the results for the
corresponding effective medium, the structure demonstrates strong optical
nonlocality due to excitation of surface plasmon polaritons that can be
engineered by changing a ratio between the thicknesses of metal and dielectric
layers. In particular, this nonlocality allows the existence of an additional
extraordinary wave that manifests itself in the splitting of the TM-polarized
beam scattered at an air-metamaterial interface
Scattering Suppression from Arbitrary Objects in Spatially-Dispersive Layered Metamaterials
Concealing objects by making them invisible to an external electromagnetic
probe is coined by the term cloaking. Cloaking devices, having numerous
potential applications, are still face challenges in realization, especially in
the visible spectral range. In particular, inherent losses and extreme
parameters of metamaterials required for the cloak implementation are the
limiting factors. Here, we numerically demonstrate nearly perfect suppression
of scattering from arbitrary shaped objects in spatially dispersive
metamaterial acting as an alignment-free concealing cover. We consider a
realization of a metamaterial as a metal-dielectric multilayer and demonstrate
suppression of scattering from an arbitrary object in forward and backward
directions with perfectly preserved wavefronts and less than 10% absolute
intensity change, despite spatial dispersion effects present in the composite
metamaterial. Beyond the usual scattering suppression applications, the
proposed configuration may serve as a simple realisation of scattering-free
detectors and sensors
Interface modes in nanostructured metal-dielectric metamaterials
We study surface modes at an interface separating two different layered metal-dielectric metamaterials. We demonstrate that, in a sharp contrast to the effective-medium approach predicting a single interface mode with the surface-plasmon dispersion, the transfer-matrix method reveals the existence of three types of localized interface modes, including a backward interface mode. These results confirm that metal-dielectric nanostructured metamaterials can demonstrate strong optical nonlocality due to the excitation of surface plasmon polaritons.The authors acknowledge the support from a mega-grant
of the Ministry of Education and Science of Russian Federation
(Russia), EPSRC (UK), Dynasty Foundation, and Australian
Research Council through the Discovery and Center
of Excellence Programs (Australia)
АNALYSIS OF OPTICAL METHODS FOR MONITORING THE WORKING SURFACE STATE OF THE GRINDING WHEEL
The article describes an analysis of non-contact optical methods for monitoring linear wear and the working surface condition of the grinding wheel during dry grinding. The presented methods are based on computer processing of photo and video materials, 3D models surface construction of the grinding wheel, the machine vision and using of the optical equipment. The advantages and disadvantages of this methods were analyzed. As a result of the conducted research, it was concluded that the usable area of the considered methods depends on the circle material, cutting parameters, control objectives, including the requirement for on-line control, and also the available material and technical equipment
Nonlocal effective parameters of multilayered metal-dielectric metamaterials
We consider multilayered metal-dielectric metamaterials composed of alternating nanolayers of two types and calculate the components of their effective dielectric permittivity tensors as functions of both frequency and wave vector. We demonstrate that such structures can be described as strongly nonlocal uniaxial effective media, and we analyze how the nonlocal permittivity tensor components are related to other manifestations of strong spatial dispersion in such structures, and how the resonance of permittivity depends on the propagation direction
Vector Beams with Parabolic and Elliptic Cross-Sections for Laser Material Processing Applications
Beam profile engineering, where a desired optical intensity distribution can
be generated by an array of phase shifting (or amplitude changing) elements is
a promising approach in laser material processing. For example, a spatial light
modulator (SLM) is a dynamic diffractive optical element allowing for
experimental implementations of controllable beam profile. Scalar Mathieu beams
have elliptical intensity distribution perceivable as optical knives in the
transverse plane and scalar Weber beams have a parabolic distribution, which
enables us to call them optical shovels. Here, we introduce vector versions of
scalar Mathieu and Weber beams and use those vector beams as a basis to
construct controllable on-axis phase and amplitude distributions with
polarization control. Further, we generate individual components of optical
knife and shovel beams experimentally using SLMs as a toy model and report on
our achievements in the control over the beam shape, dimensions and
polarization along the propagation axis
Nonlocal effective medium model for multilayered metal-dielectric metamaterials
We study layered metal-dielectric structures, which can be considered as a simple example of nanostructured metamaterials. We analyze the dispersion properties of such structures and demonstrate that they show strong optical nonlocality due to excitatio
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