5,174 research outputs found
Deep sub-wavelength nanofocusing of UV-visible light by hyperbolic metamaterials
Confining light into a sub-wavelength area has been challenging due to the natural phenomenon of diffraction. In this paper, we report deep sub-wavelength focusing via dispersion engineering based on hyperbolic metamaterials. Hyperbolic metamaterials, which can be realized by alternating layers of metal and dielectric, are materials showing opposite signs of effective permittivity along the radial and the tangential direction. They can be designed to exhibit a nearly-flat open isofrequency curve originated from the large-negative permittivity in the radial direction and small-positive one in the tangential direction. Thanks to the ultraflat dispersion relation and curved geometry of the multilayer stack, hyperlens can magnify or demagnify an incident beam without diffraction depending on the incident direction. We numerically show that hyperlens-based nanofocusing device can compress a Gaussian beam down to tens-of-nanometers of spot size in the ultraviolet (UV) and visible frequency range. We also report four types of hyperlenses using different material combinations to span the entire range of visible frequencies. The nanofocusing device based on the hyperlens, unlike conventional lithography, works under ordinary light source without complex optics system, giving rise to practical applications including truly nanoscale lithography and deep sub-wavelength scale confinement.1165Nsciescopu
Towards all-dielectric metamaterials and nanophotonics
We review a new, rapidly developing field of all-dielectric nanophotonics
which allows to control both magnetic and electric response of structured
matter by engineering the Mie resonances in high-index dielectric
nanoparticles. We discuss optical properties of such dielectric nanoparticles,
methods of their fabrication, and also recent advances in all-dielectric
metadevices including couple-resonator dielectric waveguides, nanoantennas, and
metasurfaces
Doubly resonant second-harmonic generation of a vortex beam from a bound state in the continuum
Second harmonic generation in nonlinear materials can be greatly enhanced by
realizing doubly-resonant cavities with high quality factors. However,
fulfilling such doubly resonant condition in photonic crystal (PhC) cavities is
a long-standing challenge, because of the difficulty in engineering photonic
bandgaps around both frequencies. Here, by implementing a second-harmonic bound
state in the continuum (BIC) and confining it with a heterostructure design, we
show the first doubly-resonant PhC slab cavity with W
conversion efficiency under continuous wave excitation. We also report the
confirmation of highly normal-direction concentrated far-field emission pattern
with radial polarization at the second harmonic frequency. These results
represent a solid verification of previous theoretical predictions and a
cornerstone achievement, not only for nonlinear frequency conversion but also
for vortex beam generation and prospective nonclassical sources of radiation.Comment: revtex4-2, 7 pages, 5 figures, conference CLE
Invisibility and Cloaking: Origins, Present, and Future Perspectives
The development of metamaterials, i.e., artificially structured materials that interact with waves in unconventional ways, has revolutionized our ability to manipulate the propagation of electromagnetic waves and their interaction with matter. One of the most exciting applications of metamaterial science is related to the possibility of totally suppressing the scattering of an object using an invisibility cloak. Here, we review the available methods to make an object undetectable to electromagnetic waves, and we highlight the outstanding challenges that need to be addressed in order to obtain a fully functional coating capable of suppressing the total scattering of an object. Our outlook discusses how, while passive linear cloaks are fundamentally limited in terms of bandwidth of operation and overall scattering suppression, active and/or nonlinear cloaks hold the promise to overcome, at least partially, some of these limitations.AFOSR Award FA9550-13-1-0204NSF CAREER Award ECCS-0953311DTRA YIP Award HDTRA1-12-1-0022Electrical and Computer Engineerin
Subwavelength Surface Plasmons Based on Novel Structures and Metamaterials
With the rapid development of nanofabrication technology and powerful computational tools over the last decade, nanophotonics has enjoyed tremendous innovation and found wide applications in ultrahigh-speed data transmission, sensitive optical detection, manipulation of ultra-small objects, and visualization of nanoscale patterns. Surface plasmon-based photonics (or plasmonics) merges electronics and photonics at the nanoscale, creating the ability to combine the superior technical advantages of photonics and electronics on the same chip. Plasmonics focuses on the innovation of photonic devices by exploiting the optical property of metals. In particular, the oscillation of free electrons, when properly driven by electromagnetic waves, would form plasmon-polaritons in the vicinity of a metal surface and potentially result in extreme light confinement, which may beat the diffraction limit faced by conventional photonic devices and enable greatly enhanced light-matter interactions at the deep subwavelength scale. The objective of this dissertation is to develop subwavelength or deep subwavelength plasmonic waveguides and explore their integration on conventional dielectric platforms for multiple applications. Three novel structures (or mechanisms) are employed to develop and integrate nanoplasmonic waveguides; each consists of one part of the dissertation. The first part of this dissertation covers the design, fabrication, and demonstration of two-dimensional and three-dimensional metal-insulator-metal plasmonic couplers for mode transformation between photonic and nanoplasmonic domains on the silicon-on-insulator platform. In particular, deep subwavelength plasmonic modes under 100-nm are achieved via end-fire coupling and adiabatic mode transformation at telecom wavelengths. The second part studies metallic gratings as spoof plasmonic waveguides hosting deep subwavelength surface propagation modes. Metallic gratings under different dielectric coatings are numerically investigated for terahertz and gigahertz regions. The third part proposes, explores, and experimentally demonstrates the metametal for super surface wave excitation based on multilayered metal-insulator stacks, where the dispersion of the supported surface modes can be engineered by insulator dopant films in a given metal. The final part discusses the potential applications of active plasmonics for optical sensing, modulation and photovoltaics
Integrated Spectroscopic Sensor fabricated in a novel Si3N4 platform
[ES] Esta tesis se ha centrado en el modelado, diseño y demostración experimental de un sensor espectroscópico integrado basado en un AWG (del inglés Arrayed Waveguide Grating). El dispositivo ha sido diseñado y fabricado en una nueva plataforma de nitruro de silico (Si3N4) en oxido de silico (SiO2) desarrollada en España. El trabajo realizado en esta tesis se puede dividir en dos secciones principalmente. En la primera parte, se describe el panorama general de las plataformas de Si3N4 existentes y su estado del arte, junto con la descripción de los procesos de fabricación y caracterización de nuestra plataforma de Si3N4 con 300 nm de altura en la capa de guiado. En la segunda parte, se presenta el dispositivo bautizado como Integrated Optical Spectroscopic Sensor (IOSS). El IOSS consiste en un AWG cuyo conjunto de guías de onda está dividido en dos subgupos diseñados para replicar los canales del AWG. Las guías de uno de los subgrupos contienen ventanas de sensado, que están definidas por secciones en las que el núcleo de las guías está al descubierto y, por tanto, en contacto con el medio que las rodea. De esta manera, el sensado se lleva a cabo mediante la interacción del campo evanescente con la muestra depositada. Las guías del segundo subconjunto permanecen inalteradas. Por lo tanto, el dispositivo proporciona al mismo tiempo los espectros
de sensado y de referencia. El modelo matemático del IOSS, su procedimiento de diseño y la prueba de concepto del sensor configurado para espectroscopía de absorción se describen en esta tesis.[CAT] La present tesi s'ha centrat en el modelatge, disseny i demostració experimental d'un sensor espectroscòpic integrat basat en un AWG (de l'anglès Arrayed Waveguide Grating). El dispositiu ha sigut dissenyat i fabricat en una nova plataforma de nitrur de silici (Si3N4) en òxid de silici (SiO2) desenvolupada a Espanya. El treball realitzat en aquesta tesi es pot dividir en dues seccions principalment. En la primera part, es descriu el panorama general de les plataformes de Si3N4 existents i el seu estat de l'art, juntament amb la descripció dels processos de fabricació i caracterització de la nostra plataforma de Si3N4 amb 300 nm d'altura en la capa de guiat. En la segona part, es presenta el dispositiu batejat com Integrated Optical Spectroscopic Sensor (IOSS). El IOSS consisteix en un AWG en el que el seu conjunt de guies d'ona està dividit en dos subgrups dissenyats per a replicar els canals del AWG. Les guies d'un dels subgrups conté finestres de detecció, que estan definides per seccions en les quals el nucli de les guies d'ona està al descobert i en contacte amb el mitjà que li envolta. D'aquesta manera, la detecció es duu a terme mitjançant la interacció del camp evanescent amb la mostra depositada. Les guies del segon subconjunt romanen inalterades. Per tant, el dispositiu proporciona al mateix temps els espectres de detecció de referència. El model matemàtic del IOSS, el seu procediment de disseny i la prova de concepte del sensor configurat per a espectroscopia d'absorció es descriuen en aquesta tesi.[EN] This thesis is focused on the model, design and experimental demonstration of an integrated spectroscopic sensor based on a modified Arrayed Waveguide Grating (AWG). The device has been designed and fabricated in a new silicon nitride (Si3N4) on silicon oxide (SiO2) platform developed in Spain. The work performed for this thesis can be then divided into two main sections. In the first part, an overview of the existing Si3N4 platforms and their state of art is described, alongside the report on the fabrication and characterization of our 300 nm guiding film height Si3N4 platform. On the second part, the device named Integrated Optical Spectroscopic Sensor (IOSS) is presented. The IOSS consists of an AWG which arrayed waveguides are divided into two sub-sets engineered to replicate the AWG channels. The waveguides of one of the sub-sets contain sensing windows, defined as waveguides sections which core is in contact with the surrounding media. Thus, the sensing is performed through evanescent field interaction with the sample deposited. The waveguides from the second sub-set remain isolated. Therefore, the device provides both sensing and reference spectra. The IOSS mathematical model, design procedure and proof of concept configured for absorption spectroscopy are reported in this thesis.Micó Cabanes, G. (2020). Integrated Spectroscopic Sensor fabricated in a novel Si3N4 platform [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159381TESI
The First Multichroic Receiver and Results from ACTPol.
The Cosmic Microwave Background (CMB) is a unique and powerful tool for the study of cosmology and fundamental physics. The next frontier of CMB research is to extract the wealth of cosmological information available from its polarization. Accurate measurement of this polarization signal will enable us to probe inflation, provide an alternative means to measure the neutrino mass sum and number of neutrino species; improve our understanding of dark energy; explore the reionization history of our Universe; probe the large scale structure through gravitational lensing; and enable a multitude of other astrophysical studies. The polarized signatures of the early universe are extremely weak, dominated by foregrounds, and its measurement is susceptible to instrumental effects. Extracting the information contained in these faint signals requires instruments with high sensitivity, excellent control over systematic errors, and careful data analysis.
The Atacama Cosmology Telescope Polarimeter (ACTPol) is a state-of-the-art experiment that measures CMB polarization over finer angular scales from the Atacama desert in Chile. In this thesis, I present an overview of this project and then describe my work on the project including development of a new polarization sensitive dichroic camera for ACTPol designed to increase the sensitivity of CMB telescopes and enable high precision measurements of CMB polarization; the development of novel metamaterial antireflection coatings for silicon lenses; diffraction from panel gaps; calibration of detector pass-bands; and a detailed description of my analysis of the polarization properties of extragalactic point sources discovered with the ACTPol data. I conclude with a discussion of the science of ACTPol, and the impact of my technical work on future CMB experiments.PHDPhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135767/1/dattar_1.pd
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