X-ray phase-contrast tomography (XPCT) offers a highly sensitive 3D imaging approach to investigate different disease-relevant networks from the single cell to the whole organ. We present here a concomitant study of the evolution of tissue damage and inflammation in potential target organs of the disease in the murine model of multiple sclerosis. XPCT identifies and monitors structural and cellular alterations throughout the central nervous system, but also in the gut and eye, of mice induced to develop multiple sclerosis-like disease and sacrificed at pre-symptomatic and symptomatic time points. This approach rests on a multiscale analysis to detect early appearance of imaging indicators potentially acting as biomarkers predictive of the disease. The longitudinal data permit an original evaluation of the sequential evolution of multi-organ damage in the mouse model, shedding light on the role of the gut-brain axis in the disease initiation and progression, of relevance for the human case.
Lorenzo Dominici, David Colas, Stefano Donati, Galbadrakh Dagvadorj, Antonio Gianfrate, Carlos Sánchez Muñoz, Dario Ballarini, Milena De Giorgi, Giuseppe Gigli, Marzena Szymańska, Fabrice Laussy, Daniele Sanvitto
Here we present different approaches to ultrafast pulse and polarization shaping, based on a “quantum fluid” platform of polaritons. Indeed we exploit the normal modes of two dimensional polariton fluids made of strong coupled quantum well excitons and microcavity photons, by rooting different polarization and topological states into their sub-picosecond Rabi oscillations. Coherent control of two resonant excitation pulses allows us to prepare the desired state of the polariton, taking benefit from its four-component features given by the combination of the two normal modes with the two degrees of polarization. An ultrafast imaging based on the digital off-axis holography technique is implemented to study the polariton complex wavefunction with time and space resolution. We show in order coherent control of the polariton state on the Bloch sphere, an ultrafast polarization sweeping of the Poincaré sphere, and the dynamical twist of full Poincaré states such as the skyrmion on the sphere itself. Finally, we realize a new kind of ultrafast swirling vortices by adding the angular momentum degree of freedom to the two-pulse scheme. These oscillating topology states are characterized by one or more inner phase singularities tubes which spirals around the axis of propagation. The mechanism is devised in the splitting of the vortex into the upper and lower polaritons, resulting in an oscillatory exchange of energy and angular momentum and in the emitted time and space structured photonic packets.
In the case of light emitting semiconducting polymers, different techniques have been used for the fabrication of electroluminescent devices. Experiments and characterizations have been carried out at different operating voltages and for voltage dependent emission color also combining the processability of organic materials with efficient luminescence displayed by inorganic nanocrystals (NCs). In fact, the experimental perspective to disperse emitting colloidal NCs into polymers has allowed to further engineer hybrid organic-inorganic materials introducing innovative functionalities as for instance photoluminescence conversion capabilities. This has proved of great interest for novel applications such as the fabrication of photonic crystals and, notably, of innovative solar cells showing enhanced efficiency. Here we report on the fabrication of novel active micro-optical elements made by a mixture of rod-shaped inorganic NCs dispersed into poly-dimethylsiloxane.
Exciton-polaritons, composite particles resulting from the strong coupling between excitons and photons, have shown the capability to undergo condensation into a macroscopically coherent quantum state, demonstrating strong non-linearities and unique propagation properties. These strongly-coupled light-matter particles are promising candidates for the realization of semiconductor all-optical devices with fast time response and small energy consumption. Recently, quantum fluids of polaritons have been used to demonstrate the possibility to implement optical functionalities as spin switches, transistors or memories, but also to provide a channel for the transmission of information inside integrated circuits. In this context, the possibility to extend the range of light-matter interaction up to room temperature becomes of crucial importance. One of the most intriguing promises is to use organic Frenkel excitons, which, thanks to their huge oscillator strength, not only sustain the polariton picture at room temperature, but also bring the system into the unexplored regime of ultra-strong coupling. The combination of these materials with ad-hoc designed structures may allow the control of the propagation properties of polaritons, paving the way towards their implementation of the polariton functionalities in actual devices for opto-electronic applications.
An innovative optical panel provided with an hexagonal array of refractive lenses having a properly optimized doublecurvature
profile has been simulated by ray-tracing and fabricated by injection-moulding. Such lenses are constituted by
a concave profile (having negative curvature radius) on their bottom and a convex profile (having positive curvature
radius) on their top. We demonstrate that, if compared to refractive elements with conventional geometry, bell-shaped
microlenses allow to collect incident rays within a wider angular range (so reducing the number of rays lost by TIR )
and to properly re-direct them. When installed on fluorescent tubes-based professional lighting systems, such refractive
elements allow to reduce undesirable glare as prescribed by EN12464-1 Interior Lighting Design Standards and to finely
control photometric outputs of luminaries.
Besides, bell-shaped microlenses-based films were also simulated to be applied onto a bottom-emitting lambertian
OLED. We demonstrate that, by properly tailoring both concave and convex profile shape, it is possible to increase the
outcoupling efficiency, as well as the luminous flux emitted by the exit surface, by a factor up to 1.95 and, at the same
time, to produce far-field photometric outputs characterized by uniform isocandela distribution maps with an aperture
angle up to 60°.
In this work modulation of laser emission from polymer
nano-structured lasers was explored
through three different optical techniques.
We show all optical control of polymer distributed feedback lasers based on polyfluorenes (PFO
and F8BT) by applying a gating pulse, which completely switch-off emission in the sub-ps time
scale. The switching mechanism is assigned to photo-injection of charge carriers induced by the
gate transition. This is a resonant non-linear process, that might work at high bit-rate, paving the
way toward plastic, large-scale integrated, ultrafast optical logic.
New opportunities may also be offered by two other techniques:
Two-photon two-color pumping
allows lasing action only in presence of two different pulses, one in the visible and one in the IR,
resonant with the second telecommunication window. This may allow to convert
telecommunication signal from a fiber to visible range and thus to Plastic Optical Fibers for organic
photonics. Another technique we explored uses a blend of F8BT and a photochromic material,
(1,2-bis-(5-phenyl-2-methyl-3-tienyl) perfluocyclopentene))(C4). With a UV pulse we are able to
change C4 structure, thus overlapping its absorption spectrum with F8BT emission and modulating
yellow ASE emission.
Light emitting devices (LEDs) based on colloidal semiconductor nanocrystals represent a matter of technological interest
for the development of flat panel display and lighting systems. The appealing features of these materials are the high
fluorescence efficiency, narrow ban edge emission, potential chemical stability, and tunable light emission across the
visible spectrum. However the integration of these materials in the very promising PIN technology is still challenging
due to the lack of an appropriate QD deposition technique. So far only wet deposition methods such as spin-coating and
drop-casting have been exploited to realize QD thin film. Moreover QD thermal evaporation is not possible because of
their high molecular weight. In this scenario we developed a dry, simple, and inexpensive deposition technique to
transfer semiconductor QDs on organic semiconductor materials. We exploited this technique to fabricated an
organic/inorganic hybrid red emitting device whit a doped hole transport layer.
Light emitting devices (LEDs) based on colloidal semiconductor nanocrystals represent a matter of technological interest
for the development of flat panel display and lighting systems. The appealing features of these materials are the high
fluorescence efficiency, narrow ban edge emission, potential chemical stability, and tunable light emission across the
visible spectrum. These characteristics open the way to a new class of hybrid devices in which the flexible technology of
organic LEDs can be combined with the long operating lifetime of inorganic semiconductor devices.
In particular over the last few years several hybrid device structures based on colloidal semiconductor quantum dots
(QDs) and organic material have been reported. In this paper we report on recent development in the fabrication of QDLEDs
and in particular in white hybrid LEDs.
Colloidally synthesized CdSe/ZnS core/shell semiconductor nanocrystals (NCs) show highly efficient, narrow-width and size-tunable luminescence. Moreover, they can be incorporated in polymer matrices and deposited on solid substrates by means of spin-coating techniques. When embedded between two mirrors a NCs/polymer blends microcavity is realised, thus allowing to tailor the photoluminescence spectrum of these emitters. By virtue of the quantized photonic and electronic density of states, colloidal quantum dots embedded in a single mode vertical microcavity are good candidates for the fabrication of high-efficiency emitting devices with high spectral purity and directionality.
In this paper, we have applied a new organic-inorganic hybrid technology for the fabrication by imprint lithography (IL) of vertical microcavities that embed colloidal quantum dots.
Two dielectric distributed Bragg reflectors (DBR) are evaporated on two different substrates. The active organic layer (NCs/polymer blend) is spin coated on the first DBR, whereas a lithographic pattern is realized on the second DBR, used as the IL mold. The two parts are then assembled together in an IL process in order to create a vertical microcavity. The fine control of the thickness of the active material waveguide layer can be achieved through the mold patterning depth and the IL process parameters. All the fabrication steps have been engineered in order to decrease the thermal stress of the active layer.
The effectiveness of this technology is demonstrated by the room temperature photoluminescence (PL) spectra, recorded on the fabricated microcavity, which show a sharp emission peak with a line width of 4.15 nm.
The growing interest in biological micro-array and Lab-on-Chip
(LOC) is justified by the possibility of reducing the sample
volume, processing time and costs. By means microfluidics seems to
be the prevalent tool for the integration of manifold processes in
miniaturized devices. Anyway at a sub-millimeter scale the liquid
behavior is affected by geometric confinement and wetting
properties. In order to confine the liquid sample inside the LOC
buried channels we have performed the sealing by
poly(dimethylsiloxane)~(PDMS), a silicon-based bi-component
elastomer. The filling dynamics changes at changing of the
polymer mixing ratio of the pre-polymer and the curing agent. In
fact, a different concentration of cross-linker modifies the
elastic, adhesion and wettability properties of the cover-slip
We present a controlled, well-defined pattern replication of a
micrometer template driven by a surface free energy lithographic
technique, realized by molecular aggregation in dewetting
conditions and by confining the liquid solution with geometric
boundaries. The presented technique has allowed the fabrication
of light-emitting devices, and in particular the realization of
OLEDs with an array of addressable pixels.
We present a new class of thiophene-based molecular materials with high solid-state photoluminescence efficiencies across the entire visible range. We show that full color tunability may be achieved, including white and purple, by binary blends of these materials, according to CIE standards. With some of these materials efficient electroluminescent devices were fabricated and characterized.
We present a new class of thiophene-based oligomers and polymers with widely tunable photo and electroluminescence properties and which offer great potential for many different areas of application. We were able to synthesize materials displaying high solid-state fluorescence efficiency across the entire visible range. Electroactive polymers emitting light in the near IR were obtained by chemical and/or electrochemical polymerization of oligomers of different length. The polymers also displayed electrochromism, i.e. color change when electric current flowed through the material. All compounds were characterized by great thermo and photooxidative stability. With some of these materials efficient electroluminescent devices were fabricated and characterized.
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