The daylight sky and Avogadro's number

Two methods for estimating Avogadro's number from the observation of the daylight sky are presented, both suitable for undergraduate students. One is very simple and based on simple naked-eye observation, and the other exploits a common digital camera as a photometer

Two-dimensional mapping of the asymmetric lateral coherence of thermal light

We report in this work the first experimental verification of the asymmetric lateral coherence which is a measurement of the spatio-temporal coherence by using a wide-band Young interference experiment with a fixed off-axis slit. We demonstrate the coherence properties through the measurement of the real part of the coherence factor of thermal light. We extend our recent results obtained for betatron and undulator radiations providing a robust experimental method for the two-dimensional mapping of the two-point correlation function of broadband radiation preserving the phase information. The proposed method can be used as a high-sensitivity alternative to traditional interferometry with quasi-monochromatic radiation

Radiation emission processes and properties: synchrotron, undulator and betatron radiation

Synchrotron, undulator and betatron radiations are generated from last generation and novel concept sources. The achievement of unprecedented radiation properties opens new opportunities in various research fields as well as novel potential applications. In particular, bright coherent X-rays and (Formula presented.) -rays have been recently obtained thanks to enormous efforts in technological advancements and research activities. We give in this work a uniform argumentation and comparison of the main fundamental emission processes and radiation properties of synchrotron, undulator and betatron radiations. Emphasis is given to spatial coherence and related diagnostics, a fundamental property for any \u2018modern light source\u2019 and a basis for recent important advancements

The local intrinsic curvature of wavefronts allows to detect optical vortices

We describe a method for effectively distinguishing the radiation endowed with optical angular momentum, also known as optical vortex, from ordinary light. We show that by detecting the inversion of the transverse intrinsic curvature sign (ITICS) an optical vortex can be locally recognized. The method is effective under conditions of huge importance for the exploitation of optical vortices, such as the far field of the source and access to a small fraction of the wavefront only. The validity of the method has been verified with table-top experiments with visible light, and the results show that a measurement performed over a transverse distance smaller than 4% of the beam diameter distinguishes a vortex from a Gaussian beam with a significance of 93.4%. New perspectives are considered for the characterization of vortices, with potential impact on the detection of extra-terrestrial radiation as well as on broadcast communication techniques

Measuring the complex field scattered by single submicron particles

We describe a method for simultaneous measurements of the real and imaginary parts of the field scattered by single nanoparticles illuminated by a laser beam, exploiting a self-reference interferometric scheme relying on the fundamentals of the Optical Theorem. Results obtained with calibrated spheres of different materials are compared to the expected values obtained through a simplified analytical model without any free parameters, and the method is applied to a highly polydisperse water suspension of Poly(D,L-lactide-co-glycolide) nanoparticles. Advantages with respect to existing methods and possible applications are discussed

Single-shot measurement of phase and topological properties of orbital angular momentum radiation through asymmetric lateral coherence

We show a single-shot technique to measure topological and phase properties of radiation carrying orbital angular momentum. The single-shot method is effectively described as the one-dimensional case of a more general two-dimensional approach based on scanning interferometry (asymmetric lateral coherence). The validity of the method has been experimentally verified and the applicability to ultrarelativistic sources of hard x-rays has been discussed. The method is suitable to characterize phase and topological properties of x-ray sources by using simple apertures

Analogical optical modeling of the asymmetric lateral coherence of betatron radiation

By exploiting analogical optical modeling of the radiation emitted by ultrarelativistic electrons undergoing betatron oscillations, we demonstrate peculiar properties of the spatial coherence through an interferometric method reminiscent of the classical Young's double slit experiment. The expected effects due to the curved trajectory and the broadband emission are accurately reproduced. We show that by properly scaling the fundamental parameters for the wavelength, analogical optical modeling of betatron emission can be realized in many cases of broad interest. Applications to study the feasibility of future experiments and to the characterization of beam diagnostics tools are described

Electron Beam Size Measurements Using the Heterodyne Near Field Speckles at ALBA

Experiments using the heterodyne near field speckle method (HNFS) have been performed at ALBA to characterize the spatial coherence of the synchrotron radiation, with the ultimate goal of measuring both the horizontal and vertical electron beam sizes. The HNFS technique consists on the analysis of the interference between the radiation scattered by a colloidal suspension of nanoparticles and the synchrotron radiation, which in this case corresponds to the hard x-rays (12keV) produced by the in-vacuum undulator of the NCD-Sweet beamline. This paper describes the fundamentals of the technique, possible limitations, and shows the first experimental results changing the beam coupling of the storage ring

Hyperspectral imaging with deformable gratings fabricated with metal-elastomer nanocomposites

We report the fabrication and characterization of a simple and compact hyperspectral imaging setup based on a stretchable diffraction grating made with a metal-polymer nanocomposite. The nanocomposite is produced by implanting Ag clusters in a poly(dimethylsiloxane) film by supersonic cluster beam implantation. The deformable grating has curved grooves and is imposed on a concave cylindrical surface, thus obtaining optical power in two orthogonal directions. Both diffractive and optical powers are obtained by reflection, thus realizing a diffractive-catoptric optical device. This makes it easier to minimize aberrations. We prove that, despite the extended spectral range and the simplified optical scheme, it is actually possible to work with a traditional CCD sensor and achieve a good spectral and spatial resolution

Measuring shape and size of micrometric particles from the analysis of the forward scattered field

Characterizing nano- and micro-particles in fluids still proves to be a significant challenge for both science and industry. Here, we show how to determine shape and size distributions of polydisperse water suspensions of micron-sized particles by the analysis of the field scattered in the forward direction by single particles illuminated by a laser beam. We exploit the novel Single Particle Extinction and Scattering method in connection with shear conditions which give preferred orientations to the particles passing through the scattering volume. Water suspensions of calibrated non-spherical particles, polydisperse standard monophasic mineral samples of quartz and kaolinite, and a mixture of quartz and illite are studied in detail. Application and limitation of the method are discussed