All optical switches based on the coupling of surface plasmon polaritons

We studied the potentials of All Optical Switches (AOS) based on the intensity-dependent coupling and decoupling of light into the SPP modes (Surface Plasmon Polaritons) of a sinusoidally corrugated thin metal film (TMF), due to Kerr induced refractive index changes of the surrounding dielectrics. The ideal device has two spatially separated outputs, collecting the reflected and transmitted light and the active volume can be as small as 10(-2) mm(3). Gold and PTS (poly-(2,4-hexadiyne-1,6-diol bis(p-toluene sulfonate) are the materials considered. Losses are limited to 1.5 dB,while a 20 dB extinction ratio per gate has been theoretically demonstrated with signal pulsewidths of 5-10 ps , using a maximum optical switching peak power of 11 kW

Novel Polydiacetylene-Functionalized Nanostructures for Sensing Applications

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GATA2 deficiency and MDS/AML: experimental strategies for disease modelling and future therapeutic prospects

The importance of predisposition to leukaemia in clinical practice is being increasingly recognized. This is emphasized by the establishment of a novel WHO disease category in 2016 called 'myeloid neoplasms with germline predisposition'. A major syndrome within this group is GATA2 deficiency, a heterogeneous immunodeficiency syndrome with a very high lifetime risk to develop myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML). GATA2 deficiency has been identified as the most common hereditary cause of MDS in adolescents with monosomy 7. Allogenic haematopoietic stem cell transplantation is the only curative option; however, chances of survival decrease with progression of immunodeficiency and MDS evolution. Penetrance and expressivity within families carrying GATA2 mutations is often variable, suggesting that co-operating extrinsic events are required to trigger the disease. Predictive tools are lacking, and intrafamilial heterogeneity is poorly understood; hence there is a clear unmet medical need. On behalf of the ERAPerMed GATA2 HuMo consortium, in this review we describe the genetic, clinical, and biological aspects of familial GATA2-related MDS, highlighting the importance of developing robust disease preclinical models to improve early detection and clinical decision-making of GATA2 carriers

Two-Photon Fluorescence Correlation Spectroscopy of Gold Nanoparticles under Stationary and Flow Conditions

In this work we report two-photon fluorescence correlation spectroscopy experiments run on gold nanoparticles in aqueous solution. We compare the photophysical properties of nanoparticles obtained by the Turkevich method and by laser ablation as a function of increasing laser power. Fluorescence correlation spectroscopy curves for all nanoparticles show the rotational diffusion contribution at short lag times, even if the residual rotation contrast coefficient at high excitation laser power is lower for laser ablation nanoparticles with respect to Turkevich syntheses. Moreover, in contrast to Turkevich nanoparticles, laser ablation ones do not show an increase of the number of bright tracers in the excitation volume under higher excitation power. Nanoparticles from Turkevich synthesis are also tested as possible flow tracers inside a very simple microfluidic device featuring a single straight channel. Our findings confirm that gold nanoparticles can indeed be used as extremely sensitive probes to observe local flow inside micrometric size channels, for example, such as mammalian capillaries, since it can distinguish subtle changes in flow speed, as the ones imparted by a syringe pump

THERMAL ANNEALING OF K+-NA+ ION-EXCHANGED WAVE-GUIDES

The process of thermal annealing of K+-Na+ ion-exchanged waveguides in soda lime glass is characterized and compared with a simple theoretical model. The discrepancies between theory and experiments in the case of initially thick guides disappear if the existence of a stress-induced contribution to the refractive index is assumed that is not proportional to the concentration of the doping ions. The results obtained for initially thin guides are exploited for the design of annealed single-mode channel waveguides: 0.4-dB coupling losses with commercial single-mode fibers at λ = 1.321 µm were measured

OPTICAL FIBER-POLYMER GUIDE COUPLING BY A TAPERED GRADED-INDEX GLASS GUIDE

A new four layer tapered coupler (FLTC) has been studied and tested, able to transfer light efficiently from a monomode fiber to a polymer film guide by means of an auxiliary graded index glass waveguide. A simple theory has been developed to calculate the maximum efficiency of these structures. Experiments have been performed, at λ=1.321 μm, on several FLTC samples, containing K+-Na+ ion-exchanged glass waveguides and spin coated poly-3BCMU films. Insertion losses in the range 3-6.5 dB have been measured, depending on the taper configuration. The agreement between theoretical and experimental data is good, provided that a suitable ripple of the taper profile is assumed. The application of the new coupler to future integrated waveguide systems, including passive glass components and polymer based all optical devices, is assesse

Efficient coupling between annealed K+-Na+ ion-exchanged channel waveguides and 10/125 single-mode fibers at lambda=1.321 micrometers

The process of thermal annealing of K+-Na+ ion-exchanged channel waveguides has been studied with the aim of optimizing their coupling efficiency with commercial single-mode fibers at λ=1.321 μm. Waveguides obtained in soda-lime glass slides, with mask apertures ranging between 13.4 and 2.6 μm, were characterized before the annealing by combining nearfield measurements and an etching procedure. The experimental results were successfully compared with a theoretical model based on the variational principle. The refractive index distribution of K+-Na+ ion-exchanged channel waveguides supporting one or a low number of modes was given: compared to the corresponding slab case, the refractive index step Δno remained constant, while the waveguide depth was lower. The thermal annealing process of the channels was then performed and modeled by means of the standard diffusion theory. As a result, the channel fabrication parameters for optimum guide-fiber coupling could be predicted: 0.23-dB mode mismatch losses were measured between the optimized channel and a commercial 10/125 single-mode fiber, at λ=1.321 μ

Photobleaching of polydiacetylene waveguides: A characterization of the process and patterning of optical elements

Poly-3-butoxycarbonylmethylurethane is a conjugated polymer with large third order nonlinear optical response. Photobleaching of poly-3-butoxycarbonylmethylurethane spun films by mean of a UV lamp and 488-nm laser light is characterized and modeled. The role of oxygen on the photobleaching process is discussed. Microoptic devices and holographic gratings are formed

Dendrimer-Capped Nanoparticles Prepared by Picosecond Laser Ablation in Liquid Environment

Fifth generation ethylendiamine-core poly(amidoamine) (PAMAM G5) is presented as an efficient capping agent for the preparation of metal and semiconductor nanoparticles by ps laser ablation in water. In particular, we describe results obtained with the fundamental, second and third harmonic of a ps Nd:YAG laser and the influence of laser wavelength and pulse energy on gold particle production and subsequent photofragmentation. In this framework, the role of the dendrimer and, in particular, its interactions with gold clusters and cations are accounted