1,720,998 research outputs found
Fundamental study and analytical applications of nanoparticle-enhanced laser-induced breakdown spectroscopy (NELIBS) of metals, semiconductors and insulators
No full textNanoparticle-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) is a recently proposed method to efficiently increase the LIBS emission signal of metals up to 2 orders of magnitude, by depositing metal nanoparticles (NPs) on the sample surface (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Anal Chem 85). This considerable emission enhancement has been ascribed to two effects: (1) an improvement in the ablation effect, and (2) a more efficient production of seed electrons by field emission, in turn due to the enhancement of the laser electromagnetic field induced by the NPs themselves (De Giacomo A, Gaudiuso R, Koral C, Dell’Aglio M, De Pascale O Acta Part B, 98)
3-D printed THz q-plate with a fixed rate of change of the optical axis
No full textWe report the design and test of a THz dielectric q-plate realizing a fixed rate of change of the optical axis. The device consists of space-variant birefringent slabs manufactured by 3D printing using melt extruded ABS (Acrylonitrile Butadiene Styrene). The full position-dependent electric field of the THz beam propagating through the g-plate is obtained by measuring the THz time domain signal with a standard raster scan imaging routine. The E-field azimuthal and radial wave front patterns are successfully acquired from the realized q-plate
Geometrical Dependence on the Onset of Surface Plasmon Polaritons in THz Grid Metasurfaces
Full text linkThe transmission response of metallo-dielectric grid metasurfaces is experimentally investigated
through Terahertz Time Domain Spectroscopy and the corresponding effective dielectric function is retrieved. Using a lumped element model we can determine the dependence of the effective plasma frequency (the transition frequency) on the metasurface filling factor F. The change of the transition frequency vs. F spans over one order of magnitude and sets the threshold between the metamaterial (homogeneous) and the photonic crystal (diffraction-like) regime, ruling the onset of two different Surface Plasmon Polaritons, spoof and high order. Field symmetry and spatial extension of such excitations are investigated for the possible applications of THz grid metasurfaces in bio- and chemical sensing and sub-wavelength imaging
Terahertz time-domain study of silver nanoparticles synthesized by laser ablation in organic liquid
Full text linkWe report the investigation of laser-synthesized Ag nanoparticles (Ag-NPs) in an organic liquid environment by using terahertz time-domain spectroscopy (THz-TDS) technique. Colloidal Ag-NPs with an average diameter of 10 nm in two-propanol solution through nanosecond pulsed laser ablation were synthesized. THz-TDS measurements were performed on different volumetric concentration of Ag-NPs suspensions placed in 2-mm path length quartz cuvette. Due to the dispersive and highly absorptive nature of the nano liquids, an approach based on extracting the optical properties through the changes in amplitude and phase solely around the main peak of THz waveform is developed. This approach allowed for an accurate estimation of the complex refractive index of the Metallic-NPs suspension for the different prepared volumetric concentrations. In addition, using Maxwell-Garnett theory, the NP concentration is also extracted. This method shows that the time-domain nature of the THz pulse measurement technique is extremely useful in instances where slight variations in highly dispersive samples need to be investigated
A new method for alcohol content determination of fuel oils by terahertz spectroscopy
No full textIn this study, we developed a simple method for alcohol content analysis in fuel oils by Time-Domain Terahertz (THz) Spectroscopy. Frequency dependent absorption coefficients, refractive indices, and dielectric constants were calculated from the measurements of pure fuel oils and their mixtures with ethanol. Ethanol mixtures of gasoline were modeled successfully with a simple model in which the mixture behavior was described with a basic contribution approach of pure liquids. The results suggest that there is no strong interaction between the ethanol and the molecules in the gasoline. We concluded that this new approach offers a simple and useful method to determine the concentration of ethanol in gasoline currently with a 3% (by volume) maximum absolute error. With improvements, this error would be reduced to below 1%. © 2013 IEEE
Dispersion diagram of surface plasmon polaritons from angular transmission investigation
No full textA novel, to the best of our knowledge, methodology based on the combination of experimental measurements and simulations of the wave transmission through a metasurface at different angles is presented, enabling us to identify the fundamental and first high-order mode of spoof surface plasmon polaritons (SSPPs) excited in the terahertz regime. The approach offers a new way, an alternative to standard near field imaging, to trace out the presence of SSPPs on a metal-dielectric interface
Terahertz time-domain ellipsometry: tutorial
No full textEllipsometry is extensively used in the optical regime to investigate the properties of many materials as well as to evaluate with high precision the surface roughness and thickness of thin films and multilayered systems. Due to the inherent non-coherent detection technique, data analyses in optical ellipsometry tend to be complicated and require the use of a predetermined model, therefore indirectly linking the sample properties to the measured ellipsometric parameters. The aim of this tutorial is to provide an overview of terahertz (THz) time-domain ellipsometry, which is based instead on a coherent detection approach and allows in a simple and direct way the measurement of the material response. After giving a brief description of the technology presently used to generate and detect THz radiation, we introduce the general features of an ellipsometric setup operating in the time domain, putting in evidence similarities and differences with respect to the classical optical counterpart. To back up and validate the study, results of THz ellipsometric measurements carried out on selected samples are presented
Encoded-enhancement of THZ metasurface figure of merit for label-free sensing
Full text linkWe describe an experimental strategy for the use of Terahertz (THz) metasurfaces as a platform for label-free wide range detection of the dielectric function in biological fluids. Specifically, we propose a metagrid (MG), opportunely infiltrated with a fluid and then capped, as the reference structure for sensing experiments with a high reproducibility character. By combining experiments and full-wave simulations of the transmission T of such a structure, we introduce a reliable set up where the volume of the involved analyte in each unit cell is precisely determined. The unavoidable decrease in the quality factor of the intrinsic resonances due to the lossy fluid and cap layer is circumvented using an appropriate transformation of T that amplifies the change in the MG intrinsic resonances, improving in such a way the sensor sensitivity to values close to the experimental limits. The transformed signal features delta-like peaks enabling an easy readout of frequency positions at resonances
Sensing biological fluids using Resonating Surface Plasmon Polaritons in the THz range
No full textWe study the sensitivity of two different metagrids to the presence of biological fluids on the surface. When a THz beam impinges on each metagrid capped with a dielectric substrate, peaks in transmission related to the onset of high order surface plasmon polaritons appear and allow to estimate the properties of a guest fluid filling the partition volume with a very high sensitivity, comparable with record literature values
Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy of metallic samples
No full textIn this paper an increase of 1-2 orders of magnitude in Laser Induced Breakdown Spectroscopy (LIBS) signals was obtained by depositing silver nanoparticles on metal samples. Nanoparticle-Enhanced LIBS (NELIBS) proved a robust and flexible tool for the chemical analysis of metals because the sample emission signal did not appear very affected by the size and concentration of deposited nanoparticles (NPs), respectively within a range of 10 nm of diameter and one order of magnitude of concentration. On the other hand, preliminary NELIBS tests on insulators and semiconductors did not show any significant enhancement with respect to conventional LIBS. In this paper we present a detailed investigation of the fundamental features of the NELIBS spectra, in addition to some examples of analytical applications to the quantitative analysis of metal alloys
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