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The lower energy thresholds of large wide-field gamma-ray observatories are often determined by their capability to deal with the very low-energy cosmic ray background. In fact, in observatories with areas of tens or hundreds of thousands…
Sub-angstrom spatial resolution of electron density coupled with sub-femtosecond temporal resolution is required to directly observe the dynamics of the electronic structure of a molecule after photoinitiation or some other ultrafast…
The statistical power of weak lensing measurements is principally driven by the number of high redshift galaxies whose shapes are resolved. Conventional wisdom and physical intuition suggest this is optimised by deep imaging at long (red or…
We consider the geometrical optics for refraction of a distant radio source by an interstellar plasma lens, with application to a lens with a Gaussian electron column density profile. The refractive properties of the lens are specified…
We report on the measurements of the spectra of gamma radiation generated by 855 MeV electrons in bent silicon and germanium crystals at MAMI (MAinzer MIkrotron). The crystals were 15 {\mu}m thick along the beam direction to ensure high…
We show that diffraction intensity into the First Order Laue Zone (FOLZ) of a crystal can have a strong azimuthal dependence, where this FOLZ ring appears solely because of unidirectional atom position modulation. Such a modulation was…
The Large Area Telescope on the recently launched Fermi Gamma-ray Space Telescope (formerly GLAST), with its large field of view and effective area, combined with its excellent timing capabilities, is poised to revolutionize the field of…
The possibility to convert the photon beam linear polarization into circular one at photon energies of hundreds GeV with the use of crystals is considered. The energy and orientation dependencies of refractive indexes are investigated in…
In crystal optics the special status of the rest frame of the crystal means that space-time symmetry is less restrictive of electrodynamic phenomena than it is of static electromagnetic effects. A relativistic justification for this claim…
Current $\gamma$-ray telescopes suffer from a gap in sensitivity in the energy range between 100keV and 100MeV, and no polarisation measurement has ever been done on cosmic sources above 1MeV. Past and present e$^+$e$^-$ pair telescopes are…
We show that propagating optical fields bearing an axial symmetry are not truly hollow in spite of a null electric field on-axis. The result, obtained by general arguments based upon the vectorial nature of electromagnetic fields, is of…
Light transmission or diffraction from different quantum phases of cold atoms in an optical lattice has recently come up as a useful tool to probe such ultra cold atomic systems. The periodic nature of the optical lattice potential closely…
Optical techniques are finding widespread use in analytical chemistry for chemical and bio-chemical analysis. During the past decade, there has been an increasing emphasis on miniaturization of chemical analysis systems and naturally this…
Laser guide stars with adaptive optics allow astronomical image correction in the absence of a natural guide star. Single guide star systems with a star created in the earth's sodium layer can be used to correct the wavefront in the near…
Detectors for gamma-ray astronomy are complex: they often comprise multiple sub-systems and utilize new and/or custom-developed detector components and readout electronics. Gamma rays are typically not detected directly: ground-based…
Non-invasive optical manipulation of particles has emerged as a powerful and versatile tool for biological study and nanotechnology. In particular, trapping and rotation of cells, cell nuclei and sub-micron particles enables unique…
One of the most prominent features of the $\gamma$-ray sky is the emission from our own Galaxy. The Galactic plane has been observed by Fermi-LAT in GeV and H.E.S.S. in TeV light. Fermi has modeled the Galactic emission as the sum of a…
Ultra-High Energy (UHE, $>$0.1\,PeV) $\gamma$-ray Astronomy is rapidly evolving into an expanding branch of the $\gamma$-ray astronomy with the surprising discovery of 12 PeVatrons and the detection of a handful of photons above 1 PeV.…
Attenuation of high--energy gamma rays by pair--production with UV, optical and IR background photons provides a link between the history of galaxy formation and high--energy astrophysics. We present results from our latest semi-analytic…
Transport of fluids and particles at the microscale is an important theme both in fundamental and applied science. One of the most successful approaches is to use an electric field, which requires the system to carry or induce electric…