Search results for "Optical fields"

showing 3 items of 3 documents

Apertureless scanning near-field optical microscopy: a comparison between homodyne and heterodyne approaches

2006

International audience; In coherent homodyne apertureless scanning near-field optical microscopy (ASNOM) the background field cannot be fully suppressed because of the interference between the different collected fields, making the images difficult to interpret. We show that implementing the heterodyne version of ASNOM allows one to overcome this issue. We present a comparison between homodyne and heterodyne ASNOM through near-field analysis of gold nanowells, integrated waveguides, and a single evanescent wave generated by total internal reflection. The heterodyne approach allows for the control of the interferometric effect with the background light. In particular, the undesirable backgro…

HeterodyneImage formationPhase (waves)Near and far fieldOptical fields02 engineering and technologyInterference (wave propagation)Total internal reflection01 natural sciencesDestructive interference010309 opticsOptics0103 physical sciences[SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/MicroelectronicsPhysicsTotal internal reflectionNear field opticsbusiness.industryTapered fibersNear-field opticsScanning microscopyStatistical and Nonlinear Physics021001 nanoscience & nanotechnologyAtomic and Molecular Physics and OpticsInterferometryImage formation theory[SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic0210 nano-technologybusinessScanning electron microscopy
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Accelerating wide-angle converging waves in the near field

2014

We show that a wide-angle converging wave may be transformed into a shape-preserving accelerating beam having a beam-width near the diffraction limit. For that purpose, we followed a strategy that is particularly conceived for the acceleration of nonparaxial laser beams, in contrast to the well-known method by Siviloglou et al (2007 Phys. Rev. Lett. 99 213901). The concept of optical near-field shaping is applied to the design of non-flat ultra-narrow diffractive optical elements. The engineered curvilinear caustic can be set up by the beam emerging from a dynamic assembly of elementary gratings, the latter enabling to modify the effective refractive index of the metamaterial as it is arran…

DiffractionPhysicsCurvilinear coordinatesbusiness.industryPhysics::OpticsMetamaterialNear and far fieldInvariant optical fieldsAtomic and Molecular Physics and OpticsElectronic Optical and Magnetic MaterialsAccelerationArtificially engineered materialsOpticsDiffraction theoryBroadbandCaustic (optics)businessBeam (structure)ÓpticaJournal of Optics
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Highly localized accelerating beams using nano-scale metallic gratings

2015

Spatially accelerating beams are non-diffracting beams whose intensity is localized along curvilinear trajectories, also incomplete circular trajectories, before diffraction broadening governs their propagation. In this paper we report on numerical simulations showing the conversion of a high-numerical-aperture focused beam into a nonparaxial shape-preserving accelerating beam having a beam-width near the diffraction limit. Beam shaping is induced near the focal region by a diffractive optical element that consists of a non-planar subwavelength grating enabling a Bessel signature. This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2011-29120…

PhysicsDiffractionCurvilinear coordinatesWave propagationWave propagationbusiness.industryPhysics::OpticsGratingInvariant optical fieldsAtomic and Molecular Physics and OpticsElectronic Optical and Magnetic Materialssymbols.namesakeOpticsDiffraction theorysymbolsPhysics::Accelerator PhysicsElectrical and Electronic EngineeringPhysical and Theoretical ChemistrybusinessNanoscopic scaleIntensity (heat transfer)Beam (structure)Bessel functionÓpticaOptics Communications
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