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Tellurium based material was obtained by binding nanosized tellurium grains, produced by dry vibration milling technique, with poly(methyl methacrylate) (PMMA). The morphology, structural and electrical properties of Te/PMMA films were investigated. The photoelectrical properties of the films were studied under white light illumination varying the optical power density from 2 to 170mW/cm2 and turning on and off the light cyclically. In order to determine the effects of milling technique two sets of Te/PMMA samples were produced by binding the “as received” and milled Te powders with PMMA. A quite prompt and evident photoresponse was observed for the material prepared with Te nanopowder, while not significant variations of the conductivity were detected in a reference sample fabricated with the as received coarse Te powder and illuminated in the same optical power density range. The origin of the photoconduction can be attributed to the enhancement of the ratio between TeO2 and Te phases in the nanopowder occurring during the milling stage. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Drugs delivery into the brain across the blood brain barrier has always remained a challenging task for neuroscientists. Nanotechnology is now providing new prospective in the treatment of neurological cancer, neurovascular disorders and neurodegenerative diseases. This study aims to explore whether gold nanoparticles (AuNPs) are able to cross the blood brain barrier (BBB) and more importantly whether they have cytotoxic effects after in vivo and in vitro uptake. We selected AuNPs for their stability, size controlled synthesis, relatively easy surface modification with amine and thiol groups and capability to be studied at ultrastructural level with electron microscopy. Alkanethiol pyrazol was used to stabilize AuNPs. Thiol ligands strongly bind gold molecules due to soft character of both Au and S. Nanoparticles with a mean particle size < 2 nm were obtained. These nanoparticles had an absorption spectrum at 350 nm and showed a broad emission ranging from 400 to 600 nm depending on their quantum size since their emission shift from green to red when they form clusters of ~200 nm of diameter. In order to explore in vivo uptake of gold nanoparticles, 0.2 ml of saline suspension containing AuNPs (1x105) or physiological solution (as control) were injected into the carotid artery respectively of n=3 anesthetized mice. After 90 min from administration, the animals were sacrificed and the hindbrain slices were studied with an epifluorescence microscope. A strong particleassociated florescence was observed in the Caudato Putamen region (CPu) for AuNPs treated and not for untreated control. The fluorescence shows a more evenly spread distribution in the neuronal but not in glial cells, as shown by GFAP, Iba1 and NeuN immunoistochemistry. In order to explore in vitro cellular uptake the human neuroblastoma cells SH-SY5Y were incubated with 1 ml of saline suspension containing AuNPs (1x105) at 20 min, 1, 2 and 4 hrs. AuNPs internalization was observed through Leica microscope workstation B6000 equipped for in vivo time lapse analysis and, furthermore, confirmed by transmission electron microscopy observations. The effect of AuNPs was investigated both in vivo and in vitro using caspase-3 immunoreactivity and TUNEL test which showed apoptosis. In vivo many CPu neurons loaded with AuNPs were both caspase- 3 and TUNEL labelled as in vitro neuroblastoma cells whereas glial cells were AuNPs unloaded and caspase-3 or TUNEL negatives. Our data suggest that AuNPs cross the BBB and have particular imaging properties since they cluster into the cells changing the emission spectrum from green to red. Noteworthy AuNPs are cytotoxic so they are an attractive platform for neurological diseases if specifically addressed toward target cells.

We have experimentally investigated the expansion mechanism induced by laser irradiation of H2SO4 intercalated graphite. Intercalated graphite materials irradiated by laser allows to study reactions occurring in confined chemical conditions. We find that the laser-assisted reaction process is characterized by a threshold temperature of about 140{\deg}C followed by a fast rate of heating which produces a large amount of overheated gases and causes a violent expansion of the graphite crystal. We investigate the morphological changes undergone by irradiated graphite filaments using a combination of thermal and visible imaging technique which allows for the quantitative determination of temporal evolution of the thermal field during the heating stage and exfoliation of the grain., Comment: pag 12 figure 7

Fresnel tomograms of Laguerre-Gaussian beams are found and the relation of the two-point spatial correlation function with the tomographic map is discussed. The spatial distribution and signature of vorticity of Laguerre-Gaussian modes is analyzed by measuring the two-point spatial correlation function of the one-dimensional projection of the vortex field. An interferometric approach, based on a Fourier projection algorithm, for the experimental determination of the two-point correlation function of the full complex vortex field at the cross-section plane of the recorded interference pattern is also described; this approach allows one to characterize the vortex structure and spatial coherence along the direction of propagation

An extensive characterization of the photorefractive bright soliton writing process in a lithium niobate crystal is presented. An interferometric approach based on a digital holographic technique has been used to reconstruct the complex wave field at the exit face of the crystal. Temporal evolution of both intensity and phase profile of the writing beam has been analysed. The effective changes of the refractive index of the medium during the writing process and after the soliton formation are determined from the optical phase distribution. This method provides a reliable way to observe the process of soliton formation, whereas the determination of the intensity distribution of the output beam does not show clearly whether the soliton regime has been achieved or not. Furthermore, a detailed analysis of the soliton in a steady-state situation and with different writing conditions is presented and discussed.

An approach that uses an electro-optically tunable two dimensional phase grating to enhance the resolution in digital holographic microscopy is proposed. We show that, by means of a flexible hexagonal phase grating, it is possible to increase the numerical aperture of the imaging system, thus improving the spatial resolution of the images in two dimensions. The augment of the numerical aperture of the optical system is obtained by recording spatially multiplexed digital holograms. The grating tuneability allows one to adjust the intensity among the spatially multiplexed holograms maximizing the grating diffraction efficiency. Furthermore we demonstrate that the flexibility of the numerical reconstruction allows one to use selectively the diffraction orders carryinguseful information for increasing the spatial resolution. The proposedapproach can improve the capabilities of digital holography in three-dimensionalimaging and microscopy.

We present a series of experiments to demonstrate digital holography on reflective objects at wavelength 10.6 lm of a CO2 laser using a pyrocam array. Fresnel holograms of reflective objects are recorded by a Mach–Zehnder interferometer. We describe a method for improving the accuracy of the numerical reconstructions and for compensating the loss of resolution at longer wavelength by Fresnel reconstruction of digitally recorded infrared holograms.

In recent years a variety of liquid bases optical elements have been conceived, designed and fabricated even for commercial products like digital cameras o cellular phone cameras. The impressive development of microfluidic systems in conjunction with optics has led to the creation of a completely new Science field of investigation named optofludics. Optofludics, among others topics, deals with investigation and methods for realizing liquid micro-lenses. A variety of liquid micro-lenses have been designed and realized by using different configurations. We demonstrate that a lensing effect can be obtained in an open microfluidic system by using a thin layer of liquid on a polar electric crystal such as Lithium Niobate (LiNbO3). Electrowetting patterning on LiNbO3 surface is obtained by pyroelectric effect consisting in a simple but reliable electrodes-less and circuit-less configuration. The electrodes are intrinsically embedded into the substrate. The material is functionalised by means of a micro-engineering electric filed poling process. Lens array with variable focus has been demonstrated with a large number of lens elements (10x10) on micrometric scale (aperture of single lens 100 microns).

Resolution is an important issue in inspection of objects on microscopic scale. Various approaches have been investigated to increase the optical resolution behind the diffraction limit of an optical imaging system. Demonstration that super-resolution is possible have been also established in interference microscopy. We have studied the possibility to use diffraction gratings, in different experimental configurations for increasing the aperture of an optical imaging system. The aim of the study is to demonstrate that super-resolution is possible and is a practical and viable method for a coherent optical microscope. We take benefit of the numerical reconstruction properties of DH in combination with diffraction grating to get super-resolution. Various attempts have been performed and results are presented and discussed. The approaches could be used for metrology and imaging application in various fields of engineering and biology.

In color digital holography the recording and reconstruction of three holograms, by an optical setup operating in multi-wavelength mode, is necessary. Incorrect superposition of different images at various wavelengths may occur due to the presence of chromatic aberrations. We demonstrate that the compensation of the chromatic aberrations can be achieved by using all of the information contained in the multi-wavelength digital holograms. Chromatic aberration is extracted from phase maps reconstructed at different wavelengths, resulting in perfect full color amplitude reconstructions. The method has important applications in color 3-D holographic imaging and display.

Digital holography in the mid infrared range is shown to be a feasible technique for optical metrological applications. The technique allows to reconstruct both amplitude and phase of wavefronts scattered by a 3D object. Experimental results of the method applied to the reconstruction of digitally holograms recorded at CO2 laser wavelength of 10.6 micron are reported. It is show that good reconstructions can be obtained even with the lower spatial resolution of IR recording detectors compared to visible CCD array. The results show that new prospective can be exploited by using high power CO2 laser sources in optical metrological applications.

A moire´ interferometer is used to measure the thermal expansion of two ferroelectric crystals, LiNbO3 and KTiOPO4. The crystal samples are patterned with a chromium reflective grating and used as a diffractive component in a reflective grating interferometer. The thermal expansion of all the three axes of congruent LiNbO3 and of x and y axes of the flux-grown KTiOPO4 were measured from room temperature to 200 C°. For this temperature range the thermal expansion coefficient has been modeled by a second-order polynomial and its coefficients have been estimated by accurate analysis of the resulting moire´ fringe pattern.

Lateral shear interferometry combined with digital holographic microscopy can provide quantitative optical phase measurements with the use of a new, single image, reconstruction procedure.

A method for allowing direct perfect superimposition and comparison of Fresnel-transform reconstructions of digital holograms recorded of the same object at different distances and wavelengths is proposed and demonstrated. The method takes into account the dependence of the reconstruction pixel on the distance and the wavelength by the Fresnel-transform algorithm. The method avoids the need for image scaling at the end of the reconstruction process that usually is performed in multi-wavelength digital holography. Demonstration is given by superposing the numerical reconstructions of holograms recorded at different distances and wavelengths. The method can be potentially very useful for real-time monitoring in biological processes or for recognition and ranging by multiple wavelengths of a target with fast movements or finally for very fast investigation and study of very fast processes.

We present a new method for numerically reconstructing digital holograms on tilted planes. The method is based on the angular spectrum of plane waves. Fast Fourier transform algorithm is used twice and coordinate rotation in the Fourier domain enables to reconstruct the object field on the tilted planes. Correction of the anamorphism resulting from the coordinate transformation is performed by suitable interpolation of the spectral data. Experimental results are presented to demonstrate the method for a single-axis rotation. The algorithm is especially useful for tomographic image reconstruction.

We report on the fabrication and characterization of periodic nanoscale one- and two-dimensional surface structures in congruent 500 µm thick lithium niobate crystal samples. Structures with periods from 2 µm down to around 500 nm, lateral feature sizes down to 200 nm and depths compatible with conventional waveguide fabrication, have been obtained. Such structures are fabricated by applying polarity selective etching to periodically domain reversed samples obtained by electric field poling performed by overpoling regime. Holographic lithography is used to obtain sub-micron periodic insulating gratings to be used for selective ferroelectric domain reversal. The short pitch structures are attractive in a wide range of applications ranging from nonlinear optics, for short-wavelength conversion processes or backward second-harmonic generation, to the field of photonic crystals to fabricate novel tunable photonic crystal devices or electro-optically modulated Bragg gratings. Moreover moire beating effect is used in the photolithographic process to fabricate even more complex structures which could find applications in complicated photonic bandgap devices involving for example micro-ring resonators. In order to investigate the possibility to utilize these structures for photonic crystal applications, accurate topography characterization has been performed by using different techniques. Atomic force microscope provides high-resolution information about the lateral and depth feature size of the structures, while interferometric techniques, based on digital holography, have been used for wide field information about the homogeneity and periodicity of the structures.

We demonstrate that refractive index profile of microstructure could be correctly recovered in multiwavelenght digital holographic microscope when chromatic aberration is taken into account. The chromatic aberration introduced by the optical imaging components can be can be numerically compensated in the reconstruction process. The compensation approach requires the control of the reconstructed pixel size in the image plane if a Fresnel Transformation Method is adopted to take into account the different wavelengths used to investigate the samples. Description of the method and several examples of application will be discussed.