1,721,001 research outputs found
New Propagation Effects in Semiconductors in the UV Range: Inhibition of Absorption, Negative Refraction, Anomalous Momentum States, Sub-Wavelength Imaging, and Non-Plasmonic Nanometer-size Guided Waves
No full textSecond Harmonic Generation from Nanoslits in Metal Substrates: Applications to Palladium based H2 Sensor
No full textWe conducted a theoretical investigation of second harmonic generation and other nonlinear features that result from the magnetic Lorentz force, when a single aperture is cut on a thick, opaque palladium substrate. We studied the dependences of linear pump transmission and second harmonic generation near resonance conditions, and explored the different physical mechanisms and their dependences, for example, geometrical features. We found that it is possible to exploit field localization and surface plasmon generation to enhance second harmonic generation in the regime of extraordinary transmittance of the pump field. Both transmitted and backward second harmonic generation conversion efficiencies were investigated. The results reveal that it may be possible to access several potential new applications. In particular, we demonstrated that the exploitation of a combination of nonlinear effects and enhanced transmission makes possible a palladium-based device suitable for H-2-leak-detection
New Propagation Effects in Semiconductors in the UV Range: Inhibition of Absorption, Negative Refraction, Anomalous Momentum States, and Sub-Wavelength Imaging
No full text
Enhanced and suppressed transmission through metal gratings at the plasmonic band edges
No full textExtraordinary optical transmission through metallic gratings is mediated by Fabry-Perot cavity modes inside the apertures and surface waves propagating along the grating. Anomalous features arise in the grating transmission spectrum when the optical period for the surface wave is equal to the grating pitch. The surface waves can be plasmonic in nature or due to diffracted orders propagating parallel to the surface. At optical frequencies, plasmonic effects are well separated from Wood-Rayleigh anomalies. The plasmonic band gap properties were determined with COMSOL by propagating a plasmon on a smooth Ag surface followed with a section containing a series of air gaps. The reflection spectrum for the plasmons shows a well defined frequency gap for plasmon propagation. The COMSOL simulations for light transmitted through the grating reveal anomalies in the vicinity of the plasmonic band gap. At the center frequency of the gap where surface waves are forbidden, the transmission through the grating is very low and the reflection is 98%. Standing waves are formed at the band edges and the fields become localized. At the high energy band edge the electric field localizes in the low index medium and the magnetic field in the high index medium. The field localization reverses at the low energy band edge. As a result of the localization at the band edges, the surface plasmons couple strongly to the Fabry-Perot cavity modes at the high energy band edge leading to enhanced transmission through the grating with the opposite properties for the low energy band edge. © 2011 SPIE
The role of a discontinuous free-electron density in harmonic generation from metal surfaces
No full textWe discuss a dynamical model of harmonic generation that arises from surfaces that demarcate regions of discontinuous free electron densities. These circumstances can arise from a simple metal mirror, to more complex structures such as layered structures composed of different metals or a metal and a conducting oxide. Using a modified hydrodynamic model we examine the simple case of a metal mirror, assuming the surface is characterized by an electron cloud that spills out into vacuum and shields the internal portions of the remaining medium. We also assess the relative importance of additional nonlinear sources that arise when a free electron discontinuity is present, and show that under the right circumstances both second and third harmonic generation can be very sensitive to the nature, density and thickness of the free electron cloud. Our findings suggest the possibility to control surface harmonic generation through surface charge engineering
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Negative refraction and sub-wavelength resolution below the diffraction limit usinga a semiconductor based superlens
No full textInvestigation on the interaction of Surface Plasmons (SP) with an Electro Optiic Polymer and Development of SP Optical Devices
No full textWe are designing and fabricating arrays of subwavelength SP structures in metal films and combining these structures with EO polymers to understand the interaction of the EO polymer with the enhanced electric fields of the plasmons. We have designed and modeled resonance structures to maximize extraordinary transmittance. We are making a systematic study of SP structure shapes by studying circular holes, elliptical holes and slits. Initially we have fabricated and begun optical evaluation of subwavelength slits in gold films. Slits with 32 nm width and 120nm width have been fabricated by a focused ion beam system. Preliminary optical transmittance measurements in the visible and NIR are underway and will be compared to theoretical modeling. © 2008 IEEE
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