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Optically transparent lithium fluoride (LiF) thin films, thermally evaporated on Si(100) substrates, are under investigation as novel radiation detectors based on radiophotoluminescence for imaging of the full Bragg curves of proton beams produced by a linear accelerator for proton therapy under development at ENEA C.R. Frascati. Proton irradiation induces the formation of stable colour centres in LiF, amongst which the broadband light-emitting F2 and F3+ aggregate defects, whose concentrations are locally proportional to the energy deposited in the material. Their spatial distributions in the irradiated LiF thin films and crystals are carefully measured by acquiring the latent two-dimensional visible fluorescence images with an optical microscope under blue lamp excitation. Several LiF films grown on silicon substrate were irradiated in air at increasing proton energies up to 35 MeV with their surface parallel to the particle beam and a cleaved edge perpendicularly facing it; for each sample, the fluorescence image acquired from the top surface side of the film allows to obtain the depth profile of the energy released by protons. Differences in colour centre distributions detected in LiF films with respect to LiF crystals are presented and discussed. Accurate Monte Carlo simulations allow to fully explain their experimental behaviours, paving the way towards using LiF film radiation detectors on silicon for the advanced diagnostics of proton beams at typical particle energies used for proton therapy.

© 2023 Optica Publishing Group. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved. Nonlinear silicon photonics offers unique abilities to generate, manipulate and detect optical signals in nano-devices, with applications based on field localization and large third order nonlinearity. However, at the nanoscale, inefficient nonlinear processes, absorption, and the lack of realistic models limit the nano-engineering of silicon. Here we report measurements of second and third harmonic generation from undoped silicon membranes. Using experimental results and simulations we identify the effective mass of valence electrons, which determines second harmonic generation efficiency, and oscillator parameters that control third order processes. We can then accurately predict the nonlinear optical properties of complex structures, without introducing and artificially separating the effective ¿(2) into surface and volume contributions, and by simultaneously including effects of linear and nonlinear dispersions. Our results suggest that judicious exploitation of the nonlinear dispersion of ordinary semiconductors can provide reasonable nonlinear efficiencies and transformational device physics well into the UV range. The authors thank Zack Coppens and Dana Dement for useful discussions and help with the sample. LRS, JT, and CC acknowledge to US Army Research Laboratory Cooperative Agreement N° W911NF1920279 issued by US ARMY ACC-APG-RTP and Spanish Agencia Estatal de Investigación (project no. PID2019-105089GBI00/AEI/10.130397501100011033). MAV was partially sponsored by the Army Research Laboratory under Cooperative Agreement N° W911NF2020078.

Aim This audit reviewed management practice of patients admitted to Gozo General Hospital with a head injury, to see whether guidelines are being followed. Method All patients admitted to GGH with a head injury over a twelve-month period (December 2019 – November 2020) were retrospectively reviewed. We used National Institute for Health Care Excellence (NICE) clinical guidance 176 as the standard to compare to. Results 61 patients, with a mean age 33 years, that were admitted to hospital were included. CT head was performed on 36 (59%) patients. According to NICE guidelines, CT head was warranted in these patients: 24 (39%) patients had a CT scan which may not have been indicated according to NICE guidelines. Out of the 61 patients admitted to hospital, admission was warranted in the following: 49 (80%) of admitted patients may have not needed admission. Conclusions This retrospective review suggests that a significant number of patients are being unnecessarily admitted to Gozo General Hospital following a head injury and a significant number are having an unnecessary CT head. The local issues causing this need to be identified and methods need to be introduced to better follow recommended guidelines.

In this work, we introduce a versatile metal-wire waveguide geometry, namely a four-wire waveguide, which is capable of sustaining two independent and orthogonally polarized fundamental modes, thus acting as a broadband polarization-division multiplexer. By integrating multiscale-structured grooves into the wires of such a waveguide, we demonstrate the independent manipulation of polarization-division terahertz signals.

Proton irradiation of lithium fluoride (LiF) crystals and thin films causes the formation of electronic defects, known as color centers, in the crystal lattice, some of which show photoluminescence in the visible range under blue-light excitation. With a suitable irradiation geometry, the energy density that protons deposit in the material can be recorded as a spatial distribution of these light-emitting color centers, from which a luminous replica of the proton Bragg curve can be thereafter extracted and analyzed in a fluorescence microscope. In this paper, the cases of two LiF thin films deposited on silicon substrates and of a LiF crystal, all of them transversally irradiated with a nominal 35 MeV proton beam, are considered. A comparison of the measured photoluminescent Bragg curves with Monte Carlo simulations demonstrates (i) that the Bragg peaks in the films are located at the very same positions that would be expected in the underlying silicon substrates rather than in LiF and (ii) that an even small grazing angle of the impinging proton beam is able to significantly modify the shape of the Bragg curve in the films. Both of these findings are ascribed to the effects of multiple Coulomb scattering in both the film and the substrate. The coincidence of the Bragg peak positions with those expected in the silicon substrates and the possibility of visualizing such peaks in the Bragg curves stored as latent fluorescence images in the LiF films allow one to regard them as information transducers for proton beam diagnostics and dosimetry.

We 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.

The B-Con Basic 1.0 protocol is a medical training designed to teach how to control massive external haemorrhages in emergency conditions. Spread throughout the United States since 2013, thanks to the Stop the Bleed campaign, it has seen a progressive international spread during 2016-2018. We report here data from the first 18 months of our training in Italy.Since January 2017, military Operators enlisted to the Volunteer Military Corps of the Italian Red Cross and registered to the ACS B-Con instructor database have provided B-Con courses. These instructors have provided extensive training, involving learners among military and civilian populations, especially health professionals and students. Further, they have obtained a formal adhesion to the National Stop the Bleed Day 2018.Through August 2018, we trained 1186 learners in Italy on the B-Con protocol. The learners were mainly military personnel and law enforcement agents (620 [52%]) but also students and civilian health personnel (566 [48%]).The B-Con protocol has been very well received in Italy by military and police personnel. Good results have been assessed among civilian health professionals and medical students, especially by those operators involved in the field of emergency medicine.

Fluorescent lithium fluoride detectors for X-ray projection imaging F. Bonfigli, M.A. Vincenti, R.M. Montereali ENEA, C.R. Frascati, Photonics Micro- and Nano-structures Lab., UTAPRAD-MNF, Via E. Fermi 45, 00044 Frascati (Rome), Italy E. Nichelatti ENEA, C.R. Casaccia, Optical Devices Laboratory, UTTMAT-OTT, Via Anguillarese 301, 00123 S. Maria di Galeria, Rome, Italy F. Somma, S. Heidari Bateni Università degli Studi Roma Tre, Dip. di Fisica E. Amaldi, Via della Vasca Navale 84, 00146 Rome, Italy A. Cecilia, T. Baumbach Institute for Photon Science and Synchrotron Radiation (IPS)/ANKA, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. Abstract The possibility of detecting high quality images of materials, devices and biological samples in the soft and hard X-ray spectral ranges with high spatial resolution and contrast and by using simple exposing configuration is a topical task nowadays. For this purpose, we propose the use of versatile imaging detectors based on the radiation sensitivity of lithium fluoride (LiF) to extreme ultraviolet, soft and hard X-rays [1, 2]. X-rays generate stable point defects in LiF, known as colour centres (CCs), which emit broad-band photoluminescence at visible wavelengths under optical pumping. The high dynamic response of the material to the received dose together with the atomic scale of the CCs make LiF plates, in form of thin films or crystals, extremely attractive as high-spatial-resolution radiation-imaging detectors both in absorption and phase contrast imaging configurations [1, 3]. The latent images are subsequently read by using optical fluorescence microscopes, which in the case of advanced techniques can reach spatial resolutions well below 100 nm [4]. We present lensless imaging experiments in projection mode at the TOPO–TOMO beamline of the synchrotron light source Anka (Karlsruhe, Germany) by using LiF crystals and thin films irradiated in the energy range 6–40 keV. Stable fluorescent images were formed in LiF detectors by scattered X-rays after an object had been positioned between the X-ray source and the detectors. The object used in this work is the commercial test pattern X500-200-30 (Xradia, Pleasanton, CA, USA) consisting of a gold mask (thickness 3 m) deposited on a (500500) μm2 Si3N4 window (thickness 330 nm). The LiF detectors were crystals and 1 m thick polycrystalline films deposited on glass substrates. To imprint the X-ray image of the sample on the LiF detectors, the test pattern was irradiated with several exposure times between 1 s and 60 s. The X-ray micro-radiographies were optically read with a confocal laser scanning microscope (CLSM, Nikon Eclipse 80i-C1) operating in fluorescence mode. It is worth pointing out that a 1 m LiF film was able to store high-quality and well contrasted fluorescence images of the test pattern, although X-ray attenuation length in LiF varies between 0.02-12 mm for X-ray energies in the investigated range. The stored images show edge-enhancement effects that are ascribable to diffraction processes occurring during the X-ray beam propagation after its interaction with the sample. A computer simulation was performed to calculate the incoming X-ray intensity distribution across the detector. A fairly good agreement with experimental data evidences a linear optical fluorescence response of LiF-film based detectors under the investigated conditions. This linear behaviour has been confirmed by measurements of the PL signals of F2 and F3+ CCs detected with a CLSM system for several X-ray irradiation times. Further investigations are in progress to study the exploitation of solid-state LiF detectors for X-ray lensless projection imaging experiments and applications. References [1] G. Baldacchini, F. Bonfigli, A. Faenov, F. Flora, R.M. Montereali, A. Pace, T. Pikuz, L. Reale, J. Nanoscience and Nanotechnology 3, 6 483-486, (2003). [2] S. Almaviva, F. Bonfigli, I. Franzini, A. Lai, R.M. Montereali, D. Pelliccia, A. Cedola, S. Lagomarsino, Appl. Phys. Lett. 89, 54102, (2006). [3] F. Bonfigli, A. Cecilia, S. Heidari Bateni, E. Nichelatti, D. Pelliccia, F. Somma, P. Vagovic, M.A. Vincenti, T. Baumbach and R.M. Montereali, Radiation Measurements 56, 277-280, (2013). [4] A. Ustione, A. Cricenti, F. Bonfigli, F. Flora, A. Lai, T. Marolo, R.M. Montereali, G. Baldacchini, A. Faenov, T. Pikuz, L. Reale, Appl. Phys. Lett. 88, 141107 (2006).

We present broadband X-ray lensless projection imaging experiments performed at the TopoTomo beamline of the ANKA synchrotron facility by using innovative solid-state detectors based on the formation of stable photoluminescent colour centres (CCs) in lithium fluoride (LiF) films and crystals. The peculiar features of these detectors, like very high spatial resolution (standard 250 nm) across a large field of view (> 1 cm2), wide dynamic range (> 103), versatility and easiness of use combined with the high sensitivity of the optical fluorescence microscopy reading technique, make them very attractive as recording plates for X-ray imaging. High-resolution X-ray images of a metallic test pattern were recorded and acquired with good contrast both in LiF crystals and thin LiF films. The stored CCs fluorescence images show edge-enhancement effects ascribable to diffraction processes occurring during the X-ray beam propagation after its interaction with the samples. The experimental data concerning films and crystals based LiF-detectors will be discussed and compared with computer simulations of X-ray intensity distributions. The LiF film performances are very encouraging for the exploitation of these solid-state detectors for X-ray lensless imaging applications.

To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference (60)Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy.EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a (60)Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used.EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to (60)Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in the 2-40 Gy/min range. Short- and long-term scanner stabilities were 0.5% and 1.5%, respectively; film uniformity and reproducibility were better than 0.5%.The main purpose of this study was to implement EBT3 dosimetry in the proton low-energy radiobiology line of the TOP-IMPLART accelerator, having a maximum energy of 7 MeV. Low-energy proton and (60)Co calibrated sources were used to investigate the behavior of film response vs to be written in italicum dose. The calibration in 5 MeV protons is currently used for dose assessment in the radiobiological experiments at the TOP-IMPLART accelerator carried out at that energy value.

Lithium fluoride is a well known material used for dosimetry. In the last years it was proposed and tested also as imaging detector for X-ray microscopy. Optical microscopy represents the oldest and most used imaging technique for medicine and cell biology investigations; later other imaging techniques, including electron microscopy, were introduced. The recent technological developments in the soft X-ray field, concerning sources, optics and detectors, have been increased the interest of physicians and biologists for X-ray microscopy, mainly to obtain in vivo imaging of cells. An innovative imaging detector has been proposed and tested by researchers of C.R. ENEA Frascati, as handy, versatile and compact plate for soft X-ray imaging with very high spatial resolution, wide dynamic range, large field of view and easy to read by an optical microscope. Scientific and technological applications can be foreseen in several fields, as nanotechnologies, materials, photonics, life science and microscopy (including cell imaging, also in vivo).

We present a theoretical analysis of the effects of short range surface plasmon polariton excitation on sub-wavelength bridges in metal gratings. We show that localized resonances in thin metal bridges placed within the slit of a free-standing silver grating dramatically modify transmission spectra and boost absorption regardless of the periodicity of the grating. Additionally, the interference of multiple localized resonances makes it possible to tailor the absorption properties of ultrathin gratings, regardless of the apertures' geometrical size. This tunable, narrow-band, enhanced-absorption mechanism triggered by resonant, short range surface plasmon polaritons may also enhance nonlinear optical processes like harmonic generation, in view of the large third-order susceptibility of metals.

Concept The fabrication of substrates for surface enhanced Raman spectroscopy (SERS) responding to specific analytical (sensitivity, selectivity and reproducibility) and/or technical needs (cost, large area, stability) represents a highly active field of research. Supported gold nanostructure SERS substrates are interesting because they can accomplish plasmon resonance both in the near infrared (NIR) and visible range, matching standard laser sources for Raman analysis. In this contribute, we explore two different strategies to fabricate SERS substrates based on gold nanostructures: (i) two dimensional periodic arrays of gold nano-patches fabricated by means of nano-lithographic technique; and (ii) ensembles of gold nanoparticles grown by mask-less sputtering methodology. Motivations and Objectives The exploitation of SERS as a routine analytical technique depends on development of plasmonic substrates which have to provide significant enhancement factor, stability upon interaction with analytes and a low fabrication cost. Thus, this work is aimed to (i) the engineering of plasmonic structures in terms of size, shape, and surface distribution (random or periodic) maximizing the interaction with both analytes and excitation laser source, (ii) to the optimization of the explored fabrication routes for the production of stable array of gold nanostructures on different substrates (silicon, glass, PET, PI, and supported graphene). Results and Discussion SERS substrates based on periodic array of gold nano-patches (fig. a) and ensemble of gold nanoparticles (fig. b) supported on silicon have been fabricated. The effectiveness of these SERS substrates has been investigated and tested by a probe molecule (the benzyl thiol) in order to point up and to compare specific advantages and limits.

Broad-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.

To address the effects of a novel synthetic triterpenoid, 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO), on the induction of matrix metalloproteinases 1 and 13 (MMP-1, MMP-13) by inflammatory cytokines.Human chondrosarcoma cells stimulated with inflammatory cytokines (interleukin-1beta [IL-1beta], tumor necrosis factor alpha) were used to study the effects of CDDO on the induction of MMPs and the invasion of cells through a collagen matrix.CDDO selectively reduced the induction of MMP-1 and MMP-13 at the levels of messenger RNA and protein. Treatment with CDDO prior to cytokine stimulation enhanced this inhibition, and we demonstrated that CDDO functions at the level of transcription. Additionally, CDDO reduced IL-1beta-mediated invasion of cells through a collagen matrix.This study demonstrates that CDDO is a novel inhibitor of MMP-1 and MMP-13 gene expression mediated by inflammatory cytokines. Thus, CDDO may have therapeutic potential for the inhibition of joint degradation in osteoarthritis.

To determine how interleukin-1 (IL-1), through activation of collagenase 1 (matrix metalloproteinase 1 [MMP-1]) transcription in synovial fibroblasts, contributes to cartilage degradation in rheumatoid arthritis.Primary rabbit synovial fibroblasts were transiently transfected with MMP-1 promoter/ luciferase constructs, and promoter activity in response to IL-1 was assessed. A minimal IL-1-response element was defined and used to evaluate DNA binding proteins by electrophoretic mobility shift assay and in situ ultraviolet crosslinking assay.Transcriptional activation of the MMP-1 gene by IL-1 in rabbit synovial fibroblasts required a dorsal-like element, which was located at nucleotide (nt) -3,029, as well as an activator protein 1 site at nt -77. Importantly, an IL-1-induced DNA binding activity that was specific for the dorsal-like element contained the p50 subunit of nuclear factor kappaB (NF-kappaB).These studies demonstrate, for the first time, a role for NF-kappaB in the induction of MMP-1, and suggest a mechanism of NF-kappaB-mediated cartilage degradation in rheumatoid arthritis.

Collagenase-1 (matrix metalloproteinase-1 (MMP-1)) degrades the extracellular matrix and enhances the invasive phenotype of tumor cells. v-src activated MMP-1 transcription through a series of elements in the proximal promoter, including the E2BP (nt -172), polyoma virus enhancer A3 (PEA3) (nt -94), activator protein-1 (AP-1) (nt -72), and signal transducer and activator of transcription (STAT) (nt -57) consensus sites. Of these sites, PEA3 and STAT contributed specifically to induction by v-src, whereas the remaining elements were also involved in induction by the phorbol ester phorbol myristate acetate (PMA). However, in contrast to MMP-1 induction by PMA, an AP-1 site located at nt -186 did not contribute to v-src induction. These results suggest divergence of the tyrosine kinase- and protein kinase C-dependent pathways with respect to MMP-1 transcription. v-src induced MMP-1 through mitogen-activated protein kinases, with extracellular signal-regulated kinases playing a larger role than c-jun N-terminal kinase. Retinoic acid, which inhibits the progression of certain cancers, repressed v-src-induced MMP-1 transcription. Constitutive expression of retinoic acid receptors (RARs) alpha or beta, but not gamma, or of retinoid X receptor alpha, repressed v-src-induced collagenase-1 transcription. We concluded that oncogenic induction of MMP-1 by v-src depends on signaling pathways and cis-acting sequences that are distinct from those involved in phorbol ester activation. Furthermore, v-src induction of MMP-1 may, by acting in concert with other genes, enhance matrix degradation and tumor progression, and retinoic acid and RARs may antagonize this induction in an RAR type-specific manner.

Relatively low concentrations of reactive oxygen cause reversible alterations of endothelial cell signal transduction and gene transcription. The hypothesis that low levels of oxidant stress activate retention of trans-acting proteins in the nucleus was investigated by determining time and dose requirements for oxidant-stimulated nuclear protein binding to consensus DNA sequences for nuclear factor (NF)-kappa B or activator protein 1 (AP-1). Nuclear proteins were extracted from low passage porcine aortic endothelial cells 15 min to 24 h after addition of increasing concentrations of H2O2. Electrophoretic mobility shift assays demonstrated that protein binding to NF-kappa B and AP-1 sequences increases over 1-2 h after stress relative to time-matched controls and resolves by 24 h. The selective protein kinase C inhibitor, calphostin C, prevents approximately 30% of this increase. Inhibition of tyrosine kinase activity by herbimycin A (5 microM) completely inhibits the response to H2O2. Exposure of intact cells to H2O2 increases substrate phosphorylation in pp60src immunoprecipitates. The activity of pp60src in immunoprecipitates from control cells or of recombinant pp60src increases after in vitro addition of H2O2. H2O2-stimulated pp60src activity is reduced by pretreatment of the enzyme preparation with N-acetylcysteine. These data indicate that oxidants increase nuclear levels of trans-acting factors in endothelial cells and that these increases require oxidant-sensitive changes in both tyrosine and serine/threonine phosphorylations.

Organic light emitting devices have improved greatly in recent years, so they are now widely used in displays and lighting. Annealing processes in different atmospheres strongly affect their performance, as when the active material is the small molecule Alq3. In particular, a significant increase in the photoluminescence is observed in thin films of this molecule between 150 and 180 °C, before physical destruction of the films sets in at higher temperatures. This phenomenon is attributed to a phase transition to a novel morphological aggregation of the molecules in the film, which has yielded a much improved optical material for luminescence applications, and seems to apply to other molecules as well.

Novel X-ray imaging detectors based on photoluminescence of colour centres in lithium fluoride (LiF) have been proposed and tested for extreme ultraviolet, soft and hard X-rays up to 10 keV. For the first time we present the optical characterisation of LiF crystals and thin films irradiated at the TOPO-TOMO beamline of synchroton light source Anka (Karlsruhe, Germany) in the energy range 6-40 keV for different exposure times. Absorption and photoluminescence spectra were analysed to study the optical response of the LiF-based detectors. High resolved X-ray imaging of commercial test patterns has been obtained on LiF crystals and films by optical readout with a confocal laser scanning fluorescence microscope. © 2012 Elsevier B.V.

Graphene, a 2D carbon sheet with a honeycomb lattice, is a two-dimensional material with outstanding thermal, mechanical, electronic and optical properties. In particular, graphene is a gapless material with high mobility that exhibits remarkably high absorption values (~2.3%) for the visible and near-infrared wavelengths. In this paper, we will illustrate some applications of graphene photonics and plasmonics, reported in literature, in different research fields and we will investigate theoretically and experimentally the linear and nonlinear properties of graphene-based nanostructures such as one-dimensional (1D) photonic crystals (PhCs) and 1D gratings. In particular, we will show how to exploit the large nonlinear response and the saturation effects of graphene monolayers, sandwiched in the defect layer of an asymmetric 1D photonic crystal, to dynamically change the structure from a perfect absorber (100%) to a mirror. We will also show how it is possible to tune the working wavelength by tilting the angle of incidence of the impinging electromagnetic field for both TE and TM polarizations. Finally, we will report on a 1D dielectric grating, incorporating a graphene monolayer, that resembles the 1D PhC optical response exploiting guided mode resonances. Therefore, the proposed nanostructures could efficiently exploit the linear and nonlinear properties of the graphene monolayer for the realization of tunable absorbers or saturable mirrors improving and boosting the performance of optical devices such as photo-detectors and short-pulse lasers. © 2014 IEEE.

The use of efficient wavelength-shifters from the vacuum-ultraviolet to the photo-sensor's range of sensitivity is a key feature in detectors for Dark Matter search and neutrino physics based on liquid argon scintillation detection. Thin film of Tetraphenyl-butadiene (TPB) deposited onto the surface delimiting the active volume of the detector and/or onto the photosensor optical window is the most common solution in current and planned experiments. Detector design and response can be evaluated and correctly simulated only when the properties of the optical system in use (TPB film + substrate) are fully understood. Characterization of the optical system requires specific, sometimes sophisticated optical methodologies. In this paper the main features of TPB coatings on different, commonly used substrates is reported, as a result of two independent campaigns of measurements at the specialized optical metrology labs of ENEA and University of Tor Vergata. Measured features include TPB emission spectra with lineshape and relative intensity variation recorded as a function of the film thickness and for the first time down to LAr temperature, as well as optical reflectance and transmittance spectra of the TPB coated substrates in the wavelength range of the TPB emission.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

A thin film of Tetraphenyl-butadiene (TPB) deposited onto the surface delimiting the active volume of the detector and/or onto the photosensor's optical window is the most common solution to down convert argon VUV scintillation light in current and planned liquid argon based experiments for dark matter searches and neutrino physics. Characterization of the main features of TPB coatings on different, commonly used substrates is reported, as a result of measurements at the specialized optical metrology labs of ENEA and University of Tor Vergata. Measured features include TPB emission spectra with lineshape and relative intensity variation recorded as a function of the film thickness and for the first time down to LAr temperature, as well as optical reflectance and transmittance spectra of the TPB coated substrates in the wavelength range of the TPB emission.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

Graphene is a perfect two-dimensional (2D) carbon sheet in honeycomb lattice with unique, multi-faceted properties. Very recently plasmons have been identified in graphene thus opening a new research field called “graphene plasmonics” which provides a suitable alternative to noble-metal plasmonics, since the associated surface plasmons (SPs) exhibit much larger light confinement abilities and relatively long propagation distances, with the advantage of being highly tunable via electrostatic gating. Moreover graphene can be efficiently integrated in photonic nanostructures in order to increase the optical absorption in the visible and infrared regions (graphene photonics). In this paper we will illustrate some applications of graphene plasmonics and graphene photonics, reported in literature, in different research fields and we will review our recent numerical and experimental results concerning the linear and nonlinear optical response of graphene plasmonic and photonic nanostructures emphasizing their interaction in terms of absorption and optical resonances.

We experimentally demonstrate the possibility to implement an optical bio-sensing platform based on the shift of the plasmonic band edge of a 2D-periodic metal grating. Several 2D arrangements of square gold patches on a silicon substrate were fabricated using electron beam lithography and then optically characterized in reflection. We show that the presence of a small quantity of analyte, i.e. isopropyl alcohol, deposited on the sensor surface causes a dramatic red shift of the plasmonic band edge associated with the leaky surface mode of the grating/analyte interface, reaching sensitivity values of ~650nm/RIU. At the same time, dark field microscopy measurements show that the spectral shift of the plasmonic band edge may also be detected by observing a change in the color of the diffracted field. Calculations of both the spectral shift and the diffracted spectra variations match the experimental results very well, providing an efficient mean for the design of sensing platforms based on color observation.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We experimentally demonstrate the color tuning abilities of two-dimensional periodic arrays of gold nano-patches on silicon substrate. We observe that changes in the geometrical parameters of the array can shift significantly the plasmonic resonance that occurs at the edge of the plasmonic band gap. Experimental proof of this shift is provided by the observation of an important change in the color of the diffracted field. Calculations of the diffracted spectra match the observed color changes very well and provide an efficient means for the design of sensing platforms based on color observation.

In this paper we review our recent advances in subwavelength plasmonic structures in linear and nonlinear regimes. We show several examples of subwavelength plasmonic devices in different configurations and schemes. We emphasize how these devices can be exploited for many applications, such as sensing, spectroscopy, photovoltaics and optical communications. Finally we will illustrate some challenges that are still open and need to be fulfilled.

We experimentally investigate the nonlinear response of two-dimensional periodic arrays composed of gold nanopatches on silicon substrate, functionalized by means of a conjugated rigid thiol. The surface-enhanced Raman scattering (SERS) response is empirically evaluated using a laser source operating in the visible spectral range at λ = 633 nm. Nonlinear results are then correlated to optical and structural properties of the samples under investigation. SERS mapping and estimation of the SERS enhancement factor are examined to determine stability and reproducibility of the results, highlighting also the contribution of the plasmonic resonance excited in the two-dimensional periodic array, and the dependence on the numerical aperture of the microscope objective used in the micro-Raman system.

In this paper we describe the fabrication of a periodic, two-dimensional arrangement of gold square patches on a Silicon substrate, and highlight technological limitations due to the roughness of the metal layer. Scanning Electron Microscope (SEM) and Atomic Force Microscope analyses are also reported showing that the geometrical parameters obtained are almost identical to the nominal parameters of the simulated structure. The device is functionalized by means of a conjugated rigid thiol forming a very dense, closely packed, reproducible 18 A–thick, self-assembled monolayer. The nonlinear response of the 2D array is characterized by means of a micro-Raman spectrometer and it is compared with a conventional plasmonic platform consisting of a gold nano-particles ensemble on Silicon substrate, revealing a dramatic improvement in the Raman signal. The SERS response is empirically investigated using a laser source operating in the visible range at 633 nm. SERS mapping and estimation of the provided SERS enhancement factor (EF) are carried out to evaluate their effectiveness, stability and reproducibility as SERS substrate. Moreover, we take advantage of the simple geometry of this 2D array to investigate the dependence of the SERS response on the number of total illuminated nano-patches.

The influence of Pb2+ doping on the optical properties of LiF crystals before and after irradiation with X-ray was studied by using optical absorption and photoluminescence measurements. After irradiation it was observed an increase of the absorption due to primary and aggregate electronic defects together with a higher photoluminescence signals associated with the F2 and F3+ colour centres in doped samples compared with the undoped ones.

Tl+-doped lithium fluoride crystals exhibit very interesting properties concerning the formation of colour centres after X-rays irradiation. The presence of Tl+ ions, even in small concentrations, increases the number of traps which stabilize the H-centre aggregates. These H-centre aggregates become smaller and their number increases, inducing two sets of trapping levels. Photoluminescence measurements after subsequent thermal bleaching of the thermoluminescence peaks show a faster decreasing of the F3+ centres, in three steps, compared with the F2 ones. The F-H recombination processes may induce the excitation-emission transitions of Tl+-ions.

A two-dimensional photonic crystal microcavity coupled with a waveguide is proposed to realise a high sensitive force sensor, designed on a GaAs membrane. A theoretical model is developed to evaluate the change of the refractive index induced by the application of the force onto a sensing surface. A linear calibration curve is obtained relating the resonant drop position to the applied force.