Eyal Shekel

Gaussian content as a laser beam quality parameter

We propose the Gaussian content (GC) as an optional quality parameter for the characterization of laser beams. It is defined as the overlap integral of a given field with an optimally defined Gaussian. The definition is especially suited for applications where coherence properties are targeted. Mathematical definitions and basic calculation procedures are given along with results for basic beam profiles. The coherent combination of an array of laser beams and the optimal coupling between a diode laser and a single-mode fiber are elaborated as application examples. The measurement of the GC and its conservation upon propagation are experimentally confirmed.

Study of Magnetic Materials Using Spin-Resolved Circularly-Polarized Resonant Photoemission

We have recently demonstrated that it is possible to obtain spin-resolved valence band spectra with a very high degree of spin polarization from macroscopically non-magnetic transition metal materials if the excitation light is circularly polarized and has an energy close to the cation 2p3/2 (L3) white line. Using the layered compound Sr2CuO2Cl2 as a test system, we report in this paper that the degree of spin polarization is strongly dependent on the transition metal 3d orbital orientation relative to the Poynting vector of the light.

Optimal spatial distribution of photodetector array using information theory

Information theory is used to predict an optimal spatial distribution of a given number of photodetectors. We compare our results with the known distribution in the human eye. The optimization takes into account eye movement which leads to different optimal arrays depending on the time scales of the visual information. When the visual data contains mixed time scales, maximum information flow is achieved by an array distribution consisting of both a large uniform low resolution region, and a smaller high resolution region, as in the human retina. Optimal ratios of areas and densities of these two regions are calculated as a function of the number of eye movements. The results lend support to the hypothesis that the retina is an information theoretically optimal processor.