Low energy ions coming from the quite solar wind are considered among the causes of potential damage of the optical instrumentation and components on board of ESA Solar Orbiter. Predictions of space radiation parameters are available for instruments on board of such mission. Accelerators are commonly used to reproduce the particle irradiation on a spacecraft during its lifetime at the ground level. By selecting energies and equivalent doses it is possible to replicate the damage induced on space components. Implantation of Helium ions has been carried out on different single layer thin films at LEI facility at Forschungszentrum Dresden-Rossendorf varying the total dose. Profile of the implanted samples has been experimentally recovered by SIMS measurements. The change in reflectance performances of such coatings has been experimentally evaluated and modelled. The outcomes have been used to verify the potential impact on the METIS instrument and to drive the optimization of the M0 mirror coating..
Extreme Ultraviolet (EUV) multilayer (ML) technology has been intensively applied in many scientific and technological fields such as solar physics and photolithography. More recently, the advent of free electron lasers (FEL) emitting bright sub-ps pulses with very high quality in term of intensity stability, coherence and temporal shape has encouraged the usage of multilayer coatings also in the transport and manipulation of FEL radiation. In fact, conventional single layers coated mirrors provide negligible reflectance in the EUV spectral range whereas ML mirrors can reach high efficiency at normal incidence without affecting the pulses characteristics. Such optical elements have been also exploited at FERMI@ELETTRA FEL where novel multilayer coatings specifically conceived for pump and probe experiment and ultrafast absorption spectroscopy have been designed. The main results are reported.
Metallic nanostructures are widely studied because of their peculiar optical properties. They possess characteristic
absorbance spectra with a peak due to plasmonic resonance. This feature is directly dependent on the nanostructures
shape, size, distribution and environment surrounding them. This makes them good candidates for a variety of
applications, such as localized surface plasmon resonance sensing (LSPR), surface-enhanced Raman scattering (SERS)
and photovoltaics. A well established technique used to create nanoisland on flat substrates is performing a thermal
treatment after the deposition of a thin metal film. While the most widely investigated metal in this context is gold, we
have extended our investigation to palladium, which is interesting for sensing applications because it has an excellent
hydrogen absorption ability. The morphological properties of the nanoisland depend mainly on the starting thickness of
the deposited layer and on the annealing parameters, temperature and duration. The deposition and annealing process has
been investigated, and the resulting samples has been tested optically and morphologically in order to optimize the
structures in view or their application for sensing purposes.
Graphene–metals interfaces are investigated in many subject areas both applicative and speculative. The interest mainly
stems from the possibility for CVD synthesis of large area graphene on metals. In this case the metal acts as a catalyst for
complete dehydrogenetaion of hydrocarbon precursors that leaves carbon behind at the surface. Such bilayer are also
very appealing for surface plasmon resonance devices, since graphene acts both as a protective layer and biorecognition
element. Several pairs of graphene–metal interfaces have been studied in terms of SPR performance and physicalchemical
properties at the interface. With regard to this last aspect, NEXAFS spectroscopy is a powerful method to study
single-, double-, and few- layers graphene and to illustrate any evolution of the electronic states.
Single layer thin films have been exposed to low energy alpha particles (4keV). Implanted doses are equivalent to those accumulated in 1, 2, 4 and 6 years of ESA Solar Orbiter mission operation. Two ions fluences have been considered. In order to change the total dose accumulated, for each ion flux the time of exposure was varied. Reflectance in the visible spectral range has been measured prior and after implantation. Results show no significant change in performances in gold and palladium, while a small decrease in performances is observed in iridium. The implantation rate does not seem to affect the experiment.
Probing of Hermean Exosphere By Ultraviolet Spectroscopy (PHEBUS) is a dual channels spectrometer working in the Extreme UltraViolet (EUV) and Far UltraViolet (FUV) range. It will be on board of ESA BepiColombo cornerstone mission and it will be devoted to investigate the composition, the dynamic, the formation and the feeding mechanisms of Mercury’s exosphere system. A consistent interpretation of the observational data collected by PHEBUS requires a deeply knowledge of its radiometric behavior. The Mueller’s matrix formalism can be adopted to derive an accurate radiometric model able to takes into account also the polarization state of the source observed by PHEBUS. Moreover, this theoretical model can be further verified and refined during an experimental ground calibration campaign. In this work we present the radiometric model derived for PHEBUS spectrometer together with some results obtained during the Flight Model (FM) ground calibration which is still ongoing. In particular, the obtained results employing this approach show that this is a complete and versatile method to perform the radiometric calibration of a generic space instrument.
In this work, three TiO2 thin films with thicknesses of 22.7, 48.5 and 102.9 nm were grown on Si (100) substrates by the technique of electron beam evaporation. The films were deposited at a substrate temperature of 150°C with a deposition rate of 0.3 - 0.5 A/sec. The films thicknesses were characterized by spectroscopic ellipsometry and profilometry. The surface roughness was measured by AFM obtaining RMS of less than 0.7nm. Investigations performed by XPS method have shown that stoichiometric TiO<sub>2</sub> was obtained on all the samples with no suboxide presences. Reflectance measurements of the samples were performed in EUV and SX spectral regions from 25.5 to 454.2eV using synchrotron radiation. Analyzing the refractive index N=n+<i>i</i>k of TiO<sub>2</sub> thin films, optical constants (n,k) in this energy range were both determined by fitting the Fresnel equations with least-square fitting methods.
The interest in graphene–like materials involves many research areas, including the development of biosensors devices. We have recently studied the use of graphene/metal bilayer for surface plasmon resonance (SPR) equipment devoted to detection of chemical processes and biomolecules recognition. The dual role of graphene is to protect the metal layer underneath and to enhance the bioaffinity by adsorbing biomolecules with carbon–based ring structures. Depending on the application, it may be necessary laser and chemical treatments of graphene to improve the performances of the whole device. The processing effects will be investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The use of synchrotron light is mandatory for NEXAFS analysis since a continuous EUV source of selected polarization is required. The ideas, the analysis and the results are the subjects of this work.
The European Space Agency mission Solar Orbiter (SOLO) is dedicated to the study of the solar atmosphere and heliosphere. As a part of the payload, the instrument METIS (Multi Element Telescope for Imaging and Spectroscopy) will provide images of the corona, both in the visible range and at the hydrogen Lyman-α emission line (121.6 nm). The realization of optical coatings, based on Al and MgF2, able to reflect/transmit such spectral components is, therefore, necessary. Since optical characteristics of materials in the vacuum ultraviolet range are not well studied and vary greatly with the realization process, we implemented a study of their properties in different deposition conditions. This is aimed to the realization of a custom designed filter able to transmit the 121.6 nm wavelength while reflecting visible light, and thus separating visible from ultraviolet light paths in the METIS instrument.
The practical use of graphene and graphene oxide beyond the research laboratories is strictly related to the fine tuning of
new methodologies for processing and mass–production purposes. The photoreduction processing is an innovative route
allowing exquisite control of the optoelectronic properties of graphene–like materials irradiated by coherent and
incoherent light. We have investigated the effects induced by a mercury lamp on graphene/palladium bilayer; the change
on the optical properties of the sample has been detected by using a surface plasmon resonance setup. The analysis, the
perspectives and the preliminary results are shown thereafter.
Each metal presents different characteristics when used in a surface plasmon resonance (SPR) experiment. These include
the shape of the SPR figure, the wavelength of better operation, the tendency to oxidize, the sensitivity to environmental
changes, the range of refractive indices detectable and the capability of binding to specific targets or analytes. When
choosing the metal for our SPR experiment all of these characteristics have to be taken into account. We investigate the
behavior of metals, which are less or have never been used in this kind of application, comparing their characteristics to
gold. We deeply investigate both theoretically and experimentally the behavior of palladium. This metal leads to an
inverted curve with a maximum of reflected intensity instead of a minimum. In fact, in this case we speak of Inverted
Surface Plasmon Resonance (ISPR). Aluminum and copper have also been considered because of their potentiality in
Future solar missions will investigate the Sun from very close distances and optical components are
constantly exposed to low energy ions irradiation. Single layer thin films as well as extreme ultraviolet
multilayer coatings have been exposed to low energy alpha particles (4keV). In order to change the total dose
accumulated, for each ion fluency the time of exposure was varied. The experiment was carried out
considering typical doses accumulated during the ESA Solar Orbiter mission. Results show that ion
implantation affects the performances of both single and multilayer coatings.
The study of the free-space propagation of quantum correlations is necessary for any future application of
quantum communication aiming to connect two remote locations. Here we study the propagation of a coherent
laser beam over over 144 Km (between Tenerife and La Palma Islands of the Canary archipelagos). By attenuating
the beam we also studied the propagation at the single photon level. We investigated the statistic of arrival of
the incoming photons and the scintillation of the beam.