1,720,984 research outputs found
Investigation of Terahertz and Mid-Infrared Metamaterials
No full textIn this work metamaterial devices for the terahertz (THz) and mid-infrared (Mid-IR) spectral range have been simulated, fabricated by electron beam lithography and experimentally investigated by Fourier Transform Infrared Spectroscopy. We could implement active devices for the THz range, based on high temperature superconductors, exhibiting a tunable resonant response driven by temperature. Moreover we designed and studied plasmonic devices for the mid-IR range with optimized electric field profile and performance for high sensitivity surface plasmon-based environmental sensors
Midinfrared surface plasmon sensor based on a substrateless metal mesh
No full textA midinfrared mass sensor based on high quality factor surface plasmon modes was designed, fabricated, and tested by infrared spectroscopy for the detection of nanometric layers of dielectric materials. Substrate removal below a metal mesh with period of 2 mu m results in the coupling between degenerate surface plasmon modes on the two surfaces, resulting in a quality factor up to 33 for the antisymmetric mode. The presented substrateless metal mesh integrates mass sensing capability together with midinfrared spectroscopy, and is therefore of potential interest for substance-selective environmental and biomedical sensing applications (C) 2011 American Institute of Physics. [doi:10.1063/1.3559616
Field distribution and quality factor of surface plasmon resonances of metal meshes for mid-infrared sensing
No full textWe studied surface plasmon sensors based on micrometric metal meshes by optical transmission spectroscopy as a function of the angle of incidence. The mesh period was set to 2 mu m for operation at mid-infrared wavelengths. Metal meshes on dielectric substrates were compared to suspended meshes obtained with a lift-off-free fabrication process, which reduces plasmon damping and increases the quality factor up to 25. We have numerically calculated the electric field distribution of "dark" quadrupole-like modes and found that the suspended mesh provides an enhanced interaction volume extending up to hundreds of nanometers in free space. Our sensors have been experimentally tested and they exhibited a sensitivity up to 1.4 center dot 10(-3)nm(-1), at least 1 order of magnitude better than standard mid-infrared absorption spectroscopy
Present and perspectives of the sparc thz source
No full textThe development of radiation sources in the Terahertz (THz) spectral region has become more and more interesting because of the peculiar characteristics of this radiation: it is non ionizing, it penetrates dielectrics, it is highly absorbed by polar liquids, highly reflected by metals and reveals specific "fingerprint" absorption spectra arising from fundamentals physical processes. The THz source at SPARC is a linac-based source for both longitudinal beam diagnostics and research investigations. Its measured peak power is of the order of 108 W, very competitive with respect to other present sources. The status of the THz radiation source, in particular its generation and properties, is presented and future perspectives are discussed. Copyright © 2011 by IPAC'11/EPS-AG
Substrateless micrometric metal mesh for mid-infrared plasmonic sensors
No full textWe report on the fabrication and optical properties of thin metal films periodically patterned with square hole arrays of 2 micron pitch, which behave as substrateless plasmonic devices at mid-infrared frequencies. Large (3x3 mm(2)) meshes were fabricated by metallizing a patterned silicon nitride membrane. The mid-infrared spectra display resonant absorption lines with a Q-factor up to 22 in both transmission and reflection, due to the interaction of the radiation with surface plasmon modes on both faces of the film, allowed by substrate removal. The devices can be used to fabricate surface plasmon-based chemical sensors employing mid-infrared radiation
Dark and bright surface plasmon resonances of metal meshes for mid-infrared sensing at the nanoscale
No full textThin metal films with subwavelength hole arrays (meshes) have been fabricated for operation as optical sensors. Mid-infrared spectroscopy and electromagnetic simulations demonstrate that free-standing meshes are particularly suitable for sensing solid nanopollutants. © 2012 IEEE
Optical Properties of the Cu O Plane in the Bi2Sr2 xLaxCuO6 Family
No full textThe ab plane optical conductivity of seven single crystals, belonging to the family Bi2Sr2 amp; 8722;xLaxCuO6, has been measured for hole concentrations per Cu site 0.03 amp; 8804; p amp; 8804; 0.18, and for 6 K amp; 8804; T amp; 8804; 300 K 500 K for p 0.16 . At low doping, ten phonon lines are detected, which are due to the removal of the degeneracy of five Eu modes out of the predicted six . They are superimposed to a far infrared band, which as doping increases, closes the insulating gap thus building up the Drude term. The insulator to metal transition occurs between p 0.7 and p 0.10 consistently with a Mott mechanism. In the metallic phase, a multiband analysis identifies a Drude term plus a mid infrared band, which weakly depends on temperature and softens as p increases, like in other cuprates. The optical response of the crystal at optimum doping has been analyzed also in the superconducting phase. The Ferrel Glover Tinkham sum rule requires an integration up to amp; 937; gt; gt; 6 amp; 916; and the penetration depth is 290 nm. The bosonic spectral function includes a strong peak around 50 meV, which survives up to 500 K and, therefore, might be assigned to an electron phonon interactio
Optical properties of V2 O3 in its whole phase diagram
Full text linkVanadium sesquioxide V2O3 is considered a textbook example of Mott-Hubbard physics. In this paper, we present an extended optical study of its whole temperature/doping phase diagram as obtained by doping the pure material with M=Cr or Ti atoms (V1−xMx)2O3. We reveal that its thermodynamically stable metallic and insulating phases, although macroscopically equivalent, show very different low-energy electrodynamics. The Cr and Ti doping drastically change both the antiferromagnetic gap and the paramagnetic metallic properties. A slight chromium content induces a mesoscopic electronic phase separation, while the pure compound is characterized by short-lived quasiparticles at high temperature. This study thus provides a new comprehensive scenario of the Mott-Hubbard physics in the prototype compound V2O3
Mid-Infrared Surface Plasmon Polariton Sensors Resonant with the Vibrational Modes of Phospholipid Layers
No full textWe present an experimental study of subwavelength hole arrays in thin metal films employed as surface-enhanced optical sensors operating in the mid-infrared. The extremely narrow surface plasmon polariton spectral resonances are fitted to an analytical Fano interference model in the wavelength range 2-10 mu m. In general, the resonance frequency shifts after deposition of few-molecule layers (3.2-24 nm thickness) according to electrodynamic polarization models, hence allowing for label-free sensing. The absolute value of the shift is shown to depend on the overlap between the electric field distribution of the specific surface plasmon mode and the molecular layer, as verified by electromagnetic simulations. Biochemical sensor application is finally demonstrated by determining, from a single mid-infrared measurement, both the thickness and the absorption spectrum of phospholipid monolayers and trilayers, obtained by liposome adsorption.We present an experimental study of subwavelength
hole arrays in thin metal films employed as surface-enhanced optical
sensors operating in the mid-infrared. The extremely narrow surface
plasmon polariton spectral resonances are fitted to an analytical Fano
interference model in the wavelength range 2−10 μm. In general, the
resonance frequency shifts after deposition of few-molecule layers
(3.2−24 nm thickness) according to electrodynamic polarization
models, hence allowing for label-free sensing. The absolute value of
the shift is shown to depend on the overlap between the electric field
distribution of the specific surface plasmon mode and the molecular
layer, as verified by electromagnetic simulations. Biochemical sensor
application is finally demonstrated by determining, from a single midinfrared
measurement, both the thickness and the absorption
spectrum of phospholipid monolayers and trilayers, obtained by
liposome adsorption
- …
