The Experts below are selected from a list of 20709 Experts worldwide ranked by ideXlab platform
Ayman F Abouraddy - One of the best experts on this subject based on the ideXlab platform.
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diffraction free pulsed optical beams via space time correlations
Optics Express, 2016Co-Authors: Esat H Kondakci, Ayman F AbouraddyAbstract:Diffraction places a fundamental limitation on the distance an optical beam propagates before its size increases and spatial details blur. We show here that imposing a judicious correlation between spatial and spectral degrees of freedom of a pulsed beam can render its transverse spatial profile independent of location along the Propagation Axis, thereby arresting the spread of the time-averaged beam. Such correlation introduced into a beam with arbitrary spatial profile enables spatio-temporal dispersion to compensate for purely spatial dispersion that underlies diffraction. As a result, the spatio-temporal profile in the local time-frame of the pulsed beam remains invariant at all positions along the Propagation Axis. One-dimensional diffraction-free space-time beams are described – including non-accelerating Airy beams, despite the well-known fact that cosine waves and accelerating Airy beams are the only one-dimensional diffraction-free solutions to the monochromatic Helmholtz equation.
Esat H Kondakci - One of the best experts on this subject based on the ideXlab platform.
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diffraction free pulsed optical beams via space time correlations
Optics Express, 2016Co-Authors: Esat H Kondakci, Ayman F AbouraddyAbstract:Diffraction places a fundamental limitation on the distance an optical beam propagates before its size increases and spatial details blur. We show here that imposing a judicious correlation between spatial and spectral degrees of freedom of a pulsed beam can render its transverse spatial profile independent of location along the Propagation Axis, thereby arresting the spread of the time-averaged beam. Such correlation introduced into a beam with arbitrary spatial profile enables spatio-temporal dispersion to compensate for purely spatial dispersion that underlies diffraction. As a result, the spatio-temporal profile in the local time-frame of the pulsed beam remains invariant at all positions along the Propagation Axis. One-dimensional diffraction-free space-time beams are described – including non-accelerating Airy beams, despite the well-known fact that cosine waves and accelerating Airy beams are the only one-dimensional diffraction-free solutions to the monochromatic Helmholtz equation.
Kishan Dholakia - One of the best experts on this subject based on the ideXlab platform.
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experimental observation of modulation instability and optical spatial soliton arrays in soft condensed matter
Physical Review Letters, 2007Co-Authors: Peter J Reece, Ewan M Wright, Kishan DholakiaAbstract:: In this Letter we report observations of optically induced self-organization of colloidal arrays in the presence of unpatterned counterpropagating evanescent waves. The colloidal arrays formed along the laser Propagation Axis are shown to be linked to the breakup of the incident field into optical spatial solitons, the lateral spacing of the arrays being related to modulation instability of the soft condensed matter system.
Guoquan Zhou - One of the best experts on this subject based on the ideXlab platform.
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Structural properties of a vector hollow Gaussian beam in the far-field
Journal of Optics, 2011Co-Authors: Guoquan ZhouAbstract:The accurate description of the vector hollow Gaussian beam (HGB) in the far-field is a sum of two orthogonal terms: the TE and TM terms. The TE term denotes the electric field transverse to the Propagation Axis, and the TM term the associated magnetic field transverse to the Propagation Axis. The structural properties of a vector HGB, which are related to the energy flux distributions of the HGB and its TE and TM terms, are investigated in the far-field. The analytical expressions for the ratios of the powers of the TE and TM terms to that of the HGB are presented without any approximation. The contributions of the powers of the TE and TM terms to the power of the HGB are determined by the f-parameter and the beam order. The analytical formulae of the far-field divergence angles of the TE term, the TM term, and the HGB, which are defined by the second-order moment of the energy flux, are derived. The divergence angles depend on the f-parameter and the beam order. A relation among the divergence angles of the TE term, the TM term, and the HGB are also presented. The influences of the f-parameter and the beam order on the structural properties of a vector HGB are numerically examined in the far-field.
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Vectorial structure of helical hollow Gaussian beams in the far field
Optics Communications, 2009Co-Authors: Huiqin Tang, Guoquan Zhou, Kaicheng ZhuAbstract:Abstract The analytical vectorial structure of helical hollow Gaussian beam (HHGB) is investigated in the far field based on the vector plane wave spectrum and the method of stationary phase. The energy flux distributions of HHGB in the far-field, which is composed of TE term with the electric field transverse to the Propagation Axis, and TM term with the magnetic field transverse to the Propagation Axis, are demonstrated. The physics pictures of HHGB is illustrated from the vectorial structure, which is important to understand the theoretical aspects of both scalar and vector HHGB Propagation.
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The analytical vectorial structure of a nonparaxial Gaussian beam close to the source
Optics Express, 2008Co-Authors: Guoquan ZhouAbstract:The description of a nonparaxial Gaussian beam is made directly staring with the Maxwell’s equations. The vector angular spectrum method is used to resolve the Maxwell’s equations. As the vector angular spectrum can be decomposed into the two terms in the frequency domain, the nonparaxial Gaussian beam is also expressed as a sum of two terms. One term is the electric field transverse to the Propagation Axis, and the other term is the associated magnetic field transverse to the Propagation Axis. By means of mathematical techniques, the analytical expressions for the two terms in the source region have been derived without any approximation. The influence of the evanescent plane wave on the vectorial structure is also investigated. The results are analyzed with numerical example. This research is useful to the optical trapping and the optical manipulation.
Peter J Reece - One of the best experts on this subject based on the ideXlab platform.
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Using light scattering to resolve Brownian rotation dynamics of optically trapped Au nanorods
Journal of Applied Physics, 2018Co-Authors: Ana Andres-arroyo, Peter J ReeceAbstract:Optically trapped Au nanorods are known to adopt a preferential orientation when trapped in three dimensions at the focus of linearly polarised optical tweezers. Trapped nanorods experience both translational and rotational perturbations due to Brownian motion that are governed by the strength of the trap and associated shape-dependent hydrodynamic properties. In this study, we make use of the strong angular dependent light scattering of the localised surface plasmon resonances to interrogate the rotational dynamics of trapped nanorods principally aligned along the Propagation Axis of the trapping laser. Our measurements reveal that significant rotational dynamics can be observed whilst maintaining stable translational trapping at low powers.Optically trapped Au nanorods are known to adopt a preferential orientation when trapped in three dimensions at the focus of linearly polarised optical tweezers. Trapped nanorods experience both translational and rotational perturbations due to Brownian motion that are governed by the strength of the trap and associated shape-dependent hydrodynamic properties. In this study, we make use of the strong angular dependent light scattering of the localised surface plasmon resonances to interrogate the rotational dynamics of trapped nanorods principally aligned along the Propagation Axis of the trapping laser. Our measurements reveal that significant rotational dynamics can be observed whilst maintaining stable translational trapping at low powers.
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experimental observation of modulation instability and optical spatial soliton arrays in soft condensed matter
Physical Review Letters, 2007Co-Authors: Peter J Reece, Ewan M Wright, Kishan DholakiaAbstract:: In this Letter we report observations of optically induced self-organization of colloidal arrays in the presence of unpatterned counterpropagating evanescent waves. The colloidal arrays formed along the laser Propagation Axis are shown to be linked to the breakup of the incident field into optical spatial solitons, the lateral spacing of the arrays being related to modulation instability of the soft condensed matter system.
