1,721,181 research outputs found
Non-collinear counter-propagating beams in epsilon-near-zero films: Enhancement and inhibition of nonlinear optical processes
No full textNonlinear processes in one-dimensional photonic crystal with graphene-based defect
No full textWe investigate nonlinear properties of a one-dimensional photonic crystal with a graphene-based defect, and show that the field enhancement provided by the photonic crystal cavity enhances third harmonic generation and lowers the threshold of nonlinear processes
Absorption of harmonic light in plasmonic nanostructures
No full textSurface plasmons are known for their ability to provide large field enhancement at the interface between a metal and another medium. They can be observed in a variety of structures ranging from plain metallic films to nanoparticles and gratings. Thanks to their large electric field enhancement, surface plasmons have also been exploited for the enhancement of second and third harmonic generation. In fact, metals possess a relatively high third order susceptibility and, although dipole-allowed quadratic nonlinearities are not present in the bulk, they also display an effective second order response that arises from symmetry breaking at the surface, magnetic dipoles (Lorentz force), inner-core electrons, convective nonlinear sources, and electron gas pressure. While much attention has been devoted to achieve efficient excitation of surface plasmons to improve far-field harmonic generation, little or no attention has been paid to the dissipation of the generated harmonic light. Therefore, we undertake a discussion of both harmonic generation and absorption in simple metallic/dielectric interfaces with or without excitation of surface plasmons. We demonstrate that, despite the best efforts embarked upon to study plasmon excitation, the absorbed harmonic energy can far surpass the energy emitted in the far-field. These findings suggest that quantification of the absorbed harmonic light should be an important parameter in evaluating designs of plasmonic nanostructures for frequency mixing
Loss-compensation in 3D periodic arrays of nanoshells through quantum dots, and ε-near-zero metamaterials
No full textWe compensate for the losses in 3D arrays of nanoshells through quantum dots embedded in the nanoshells' cores, to achieve ε-near-zero metamaterials at optical frequencies. Results show loss-compensation or gain-capability in a narrow frequency band. © OSA 2012
ENZ materials and anisotropy: enhancing nonlinear optical interactions at the nanoscale
Full text linkOptical spectroscopy and microscopy of radiation-induced light-emitting point defects in lithium fluoride crystals and films
No full textBroad-band light-emitting radiation-induced F2 and F3+ electronic point defects, which are stable and laser-active at room temperature in lithium fluoride crystals and films, are used in dosimeters, tuneable color-center lasers, broad-band miniaturized light sources and novel radiation imaging detectors. A brief review of their photoemission properties is presented, and their behavior at liquid nitrogen temperatures is discussed. Some experimental data from optical spectroscopy and fluorescence microscopy of these radiation-induced point defects in LiF crystals and thin films are used to obtain information about the coloration curves, the efficiency of point defect formation, the effects of photo-bleaching processes, etc. Control of the local formation, stabilization, and transformation of radiation-induced light-emitting defect centers is crucial for the development of optically active micro-components and nanostructures. Some of the advantages of low temperature measurements for novel confocal laser scanning fluorescence microscopy techniques, widely used for spatial mapping of these point defects through the optical reading of their visible photoluminescence, are highlighted. © 2012 American Institute of Physics
Phase-Locked Second Harmonic Generation in Thin Films with Near-Zero Permittivity
No full textNonlinear processes are enhanced enormously in slabs of materials exhibiting resonant plasma features. We show the importance of phase-locked harmonic components in scenarios where absorption at the harmonic frequency is not negligible. © OSA 2013
Harmonic generation in anisotropic ENZ: Impact of nonlocalities and hot electrons
No full textWe analyze the impact of nonlocalities and hot electrons on second and third harmonic generation in anisotropic epsilon-near-zero nanostructures. Our results reveal that these contributions significantly modify both linear and nonlinear response
Versatile lithium fluoride thin-film solid-state detectors for nanoscale radiation imaging
Full text linkPoint defects in insulating materials are successfully used for radiation detectors. Among them, colour centres in lithium fluoride (LiF) are well known for application in dosimeters and in light-emitting devices and lasers. LiF
thin-film detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging application with laboratory radiation sources, e.g. laser-driven plasma sources and conventional X-ray tubes, as well as large-scale facilities, e.g. synchrotrons and free-electron lasers. Among the peculiarities of these detectors, noteworthy ones are the very high intrinsic spatial resolution ( 1 cm2) and the wide dynamic range. Moreover, they are insensitive to ambient light and no development process is needed. The latent images stored in the LiF thin layer can be read with fluorescence optical microscopy techniques.
These detectors prove to be highly versatile, as LiF is sensitive to almost any kind of radiation, including charged particles and neutrons, and can be grown in the form of polycrystalline thin films, whose photoluminescence response can be tailored trough the control of the growth conditions
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