A Lack of Resolved Near-Infrared Polarization Across the Face of M51

The galaxy M51 was observed using the Mimir instrument on the Perkins telescope to constrain the resolved H-band (1.6 $\mu$m) polarization across the galaxy. These observations place an upper limit of $P_H<0.05$ on the $H$-band polarization across the face of M51, at 0.6 arcsecond pixel sampling. Even with smoothing to coarser angular resolutions, to reduce polarization uncertainty, the $H$-band polarization remains undetected. The polarization upper limit at $H$-band, when combined with previous resolved optical polarimetry, rules out a Serkowski-like polarization dependence on wavelength. Other polarization mechanisms cannot account for the observed polarization ratio ($P_H/P{VRI} \lesssim 0.05$) across the face of M51.Comment: 4 pages, 2 figures, Accepted for publication in ApJ

Dark Forces At The Tevatron

A simple explanation of the W+dijet excess recently reported by the CDF collaboration involves the introduction of a new gauge boson with sizable couplings to quarks, but with no or highly suppressed couplings to leptons. Anomaly-free theories which include such a leptophobic gauge boson must also include additional particle content, which may include a stable and otherwise viable candidate for dark matter. Based on the couplings and mass of the Z' required to generate the CDF excess, we predict such a dark matter candidate to possess an elastic scattering cross section with nucleons on the order of sigma ~ 10^-40 cm^2, providing a natural explanation for the signals reported by the CoGeNT and DAMA/LIBRA collaborations. In this light, CDF may be observing the gauge boson responsible for the force which mediates the interactions between the dark and visible matter of our universe.Comment: 4 pages, no figure

Progress in CTEQ-TEA PDF analysis

Recent developments in the CTEQ-TEA global QCD analysis are presented. The parton distribution functions CT10-NNLO are described, constructed by comparing data from many experiments to NNLO approximations of QCD.Comment: 4 pages, 3 figures; contribution to the Proceedings of the XX Workshop on Deep Inelastic Scattering and Related Subjects, Bonn, Germany, 26-30 March, 201

A general approach for robust integrated polarization rotators

Integrated polarization rotators suffer from very high sensitivity to fabrication errors. A polarization rotator scheme that substantially increases fabrication tolerances is proposed. In the proposed scheme, two tunable polarization phase shifters are used to connect three rotator waveguide sections. By means of properly setting the polarization phase shifters, fabrication errors are compensated and perfect polarization rotation is achieved. Analytical conditions are shown that determine the maximum deviation that can be corrected with the proposed scheme. A design example is discussed, where the thermo-optic effect is used to provide the required tunable polarization phase shifting. Calculated 40dB extinction ratio is shown in presence of fabrication errors that would yield a 4dB extinction ratio in the conventional approach. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.The authors want to aknowledge Universidad de Málaga alaga, Campus de Excelencia Internacional Andalucia Tech for their support

Automatic design of high-performance fiber-chip surface grating couplers based on Floquet-Bloch mode analysis

We propose a new strategy to automatically design highly efficient fiber-chip surface grating couplers. High performance designs are achieved with a substantially reduced computational cost by combining Floquet-Bloch mode analysis with a multi-objective optimization technique (genetic algorithms)

Ultra-broadband Silicon Photonic Multimode Interference Coupler

In integrated optics, multimode interference couplers (MMIs) are used as light-wave splitters and combiners in a wide variety of devices ranging from spectrometers to sensors and coherent optical receivers. While their design and operation is generally well understood [1], the operational bandwidth remains limited. Here we present a sub-wavelength structured MMI, shown in Fig. 1(a), that overcomes this limitation and experimentally demonstrate a bandwidth exceeding 300nm at telecom wavelength, with more than 500nm bandwidth potentially attainable (as per 3D-FDTD simulations).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech