The Experts below are selected from a list of 9411 Experts worldwide ranked by ideXlab platform
Masahiro Tanaka - One of the best experts on this subject based on the ideXlab platform.
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simulation of confined and enhanced optical near fields for a long narrow aperture in a pyramidal structure on a thick metallic screen
Journal of The Optical Society of America A-optics Image Science and Vision, 2004Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:A new type of long narrow aperture in a pyramidal structure on a thick metallic screen is proposed, and optical wave scattering by this structure is simulated. This aperture structure provides high emission intensity and Small Spot Size simultaneously through excitation of the surface plasmon polaritons on the sidewalls of the pyramidal structure. Scattering of optical waves by this structure in the thick metallic screen is solved numerically with a volume integral equation by generalized conjugate residual iteration and fast Fourier transformation. The basic characteristics of the near-field intensities of the aperture are investigated in detail.
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simulation of confined and enhanced optical near fields for an i shaped aperture in a pyramidal structure on a thick metallic screen
Journal of Applied Physics, 2004Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:A modification of the I-shaped aperture proposed previously by the authors—that is, an I-shaped aperture in a pyramidal structure on a thick metallic screen—is proposed and simulated. This structure is useful in the application of the I-shaped aperture to practical near-field optical systems. Scattering of optical waves by this structure in a thick metallic screen is solved numerically using a volume integral equation by generalized conjugate residual iteration and fast Fourier transformation. It is shown that this aperture structure simultaneously provides high emission intensity and Small Spot Size through excitation of the surface plasmon polariton on the sidewalls of the aperture in the pyramid structure.
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simulation of an aperture in the thick metallic screen that gives high intensity and Small Spot Size using surface plasmon polariton
Journal of Microscopy, 2003Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:The optical wave behaviour around a subwavelength aperture in a thick metallic screen is examined through three-dimensional computer simulation. Treating the metallic screen as a dielectric slab with complex-valued permittivity, it is possible to design an aperture that simultaneously provides high intensity and Small Spot Size through the excitation of surface plasmon polaritons on the side walls of the aperture.
David Dietz - One of the best experts on this subject based on the ideXlab platform.
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electromagnetic radiation from the photoelectron plasma induced by an arbitrary photon pulse incident on a planar emitting surface in vacuum
Physics of Plasmas, 1994Co-Authors: David DietzAbstract:The electromagnetic radiation field produced by the cloud of accelerating electrons induced at a planar photoelectron emitting surface in vacuum by a photon pulse of an arbitrary time profile incident upon that surface is derived analytically in the nonrelativistic, Small‐Spot‐Size regime, this derivation providing scaling relations for the radiated fields explicit in the pulse and surface parameters. Electron cloud dynamics is discussed and integral expressions for the electric and magnetic fields at large but finite (i.e., ‘‘finitely remote’’) distances from the cloud are derived. The fields are calculated by directly summing contributions over individual electron trajectories, using exact Small‐Spot retarded times, rather than by the usual technique of first forming the electron charge and current densities and integrating them. The resulting integral representations of the finitely remote fields are correct to first order in v/c, and are valid for all time and for somewhat spatially extended charge cl...
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radiation electrodynamics of the photo electron cloud produced by an arbitrary photon pulse incident on a planar emitting surface in vacuum
Final Report, 1994Co-Authors: David DietzAbstract:Abstract : The electromagnetic radiation field produced by the cloud of accelerating electrons induced at a planar photoelectron emitting surface in vacuum by a photon pulse of arbitrary time profile incident upon that surface is derived analytically in the nonrelativistic, Small-Spot-Size regime. This derivation provides scaling relations for the radiated fields explicit in the pulse and surface parameters. Electron cloud dynamics are discussed and integral expressions for the electric and magnetic fields at large but finite (i.e., 'finitely-remote') distances from the cloud are derived. The fields are calculated by directly summing contributions over individual electron trajectories, using exact Small-Spot retarded times, rather than by the usual technique of first forming the electron charge and current densities and integrating them. The resulting integral representation of the finitely-remote fields are correct to first order in v/c and are valid for all time and for somewhat spatially extended charge clouds. These finitely-remote fields are then used to compute asymptotic radiation fields in the limit of the field point going to infinity in a suitable fashion. From these asymptotic radiation quantities in which all the integrations have been fully carried out are then derived. Illustrations of the general results for some sample pulses (constant, linear ramp, triangular, parabolic, and sq sin) are provided.
Kazuo Tanaka - One of the best experts on this subject based on the ideXlab platform.
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simulation of confined and enhanced optical near fields for a long narrow aperture in a pyramidal structure on a thick metallic screen
Journal of The Optical Society of America A-optics Image Science and Vision, 2004Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:A new type of long narrow aperture in a pyramidal structure on a thick metallic screen is proposed, and optical wave scattering by this structure is simulated. This aperture structure provides high emission intensity and Small Spot Size simultaneously through excitation of the surface plasmon polaritons on the sidewalls of the pyramidal structure. Scattering of optical waves by this structure in the thick metallic screen is solved numerically with a volume integral equation by generalized conjugate residual iteration and fast Fourier transformation. The basic characteristics of the near-field intensities of the aperture are investigated in detail.
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simulation of confined and enhanced optical near fields for an i shaped aperture in a pyramidal structure on a thick metallic screen
Journal of Applied Physics, 2004Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:A modification of the I-shaped aperture proposed previously by the authors—that is, an I-shaped aperture in a pyramidal structure on a thick metallic screen—is proposed and simulated. This structure is useful in the application of the I-shaped aperture to practical near-field optical systems. Scattering of optical waves by this structure in a thick metallic screen is solved numerically using a volume integral equation by generalized conjugate residual iteration and fast Fourier transformation. It is shown that this aperture structure simultaneously provides high emission intensity and Small Spot Size through excitation of the surface plasmon polariton on the sidewalls of the aperture in the pyramid structure.
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simulation of an aperture in the thick metallic screen that gives high intensity and Small Spot Size using surface plasmon polariton
Journal of Microscopy, 2003Co-Authors: Kazuo Tanaka, Masahiro TanakaAbstract:The optical wave behaviour around a subwavelength aperture in a thick metallic screen is examined through three-dimensional computer simulation. Treating the metallic screen as a dielectric slab with complex-valued permittivity, it is possible to design an aperture that simultaneously provides high intensity and Small Spot Size through the excitation of surface plasmon polaritons on the side walls of the aperture.
H Paganetti - One of the best experts on this subject based on the ideXlab platform.
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assessing the radiation induced second cancer risk in proton therapy for pediatric brain tumors the impact of employing a patient specific aperture in pencil beam scanning
Physics in Medicine and Biology, 2016Co-Authors: Changran Geng, M Moteabbed, Yunhe Xie, Jan Schuemann, Torunn I Yock, H PaganettiAbstract:The purpose of this study was to compare the radiation-induced second cancer risks for in-field and out-of-field organs and tissues for pencil beam scanning (PBS) and passive scattering proton therapy (PPT) and assess the impact of adding patient-specific apertures to sharpen the penumbra in pencil beam scanning for pediatric brain tumor patients. Five proton therapy plans were created for each of three pediatric patients using PPT as well as PBS with two Spot Sizes (average sigma of ~17 mm and ~8 mm at isocenter) and choice of patient-specific apertures. The lifetime attributable second malignancy risks for both in-field and out-of-field tissues and organs were compared among five delivery techniques. The risk for in-field tissues was calculated using the organ equivalent dose, which is determined by the dose volume histogram. For out-of-field organs, the organ-specific dose equivalent from secondary neutrons was calculated using Monte Carlo and anthropomorphic pediatric phantoms. We find that either for Small Spot Size PBS or for large Spot Size PBS, a patient-specific aperture reduces the in-field cancer risk to values lower than that for PPT. The reduction for large Spot Sizes (on average 43%) is larger than for Small Spot Sizes (on average 21%). For out-of-field organs, the risk varies only marginally by employing a patient-specific aperture (on average from -2% to 16% with increasing distance from the tumor), but is still one to two orders of magnitude lower than that for PPT. In conclusion, when pencil beam Spot Sizes are large, the addition of apertures to sharpen the penumbra decreases the in-field radiation-induced secondary cancer risk. There is a slight increase in out-of-field cancer risk as a result of neutron scatter from the aperture, but this risk is by far outweighed by the in-field risk benefit from using an aperture with a large PBS Spot Size. In general, the risk for developing a second malignancy in out-of-field organs for PBS remains much lower compared to PPT even if apertures are being applied.
Richard E Russo - One of the best experts on this subject based on the ideXlab platform.
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femtosecond laser ablation experimental study of the repetition rate influence on inductively coupled plasma mass spectrometry performance
Spectrochimica Acta Part B: Atomic Spectroscopy, 2008Co-Authors: Jhanis J. Gonzalez, Dayana Oropeza, Alberto Fernández, Richard E RussoAbstract:Abstract This paper demonstrates the feasibility of performing bulk chemical analysis based on laser ablation for good lateral resolution with only nominal mass ablated per pulse. The influence of repetition rate (1–1000 Hz) and scan speed (1–200 µm/s) using a low energy (30 µJ) and a Small Spot Size (~ 10 µm) UV-femtosecond laser beam was evaluated for chemical analysis of silica glass samples, based on laser ablation sampling and inductively coupled plasma mass spectrometry (ICP-MS). Accuracy to approximately 14% and precision of 6% relative standard deviation (RSD) were measured.