Isotropic Band Gaps and Freeform Waveguides Observed in Hyperuniform Disordered Photonic Solids

Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the first experimental realization of an isotropic complete photonic band gap (PBG) in a two-dimensional (2D) disordered dielectric structure. This structure is designed by a constrained-optimization method, which combines advantages of both isotropy due to disorder and controlled scattering properties due to low density fluctuations (hyperuniformity) and uniform local topology. Our experiments use a modular design composed of Al2O3 walls and cylinders arranged in a hyperuniform disordered network. We observe a complete PBG in the microwave region, in good agreement with theoretical simulations, and show that the intrinsic isotropy of this novel class of PBG materials enables remarkable design freedom, including the realization of waveguides with arbitrary bending angles impossible in photonic crystals. This first experimental verification of a complete PBG and realization of functional defects in this new class of materials demonstrates their potential as building blocks for precise manipulation of photons in planar optical micro-circuits and has implications for disordered acoustic and electronic bandgap materials

bflinks: Reliable Bugfix links via bidirectional references and tuned heuristics

Background: Data from software data repositories such as source code version archives and defect databases contains valuable information that can be used for insights (leading to subsequent improvements), in particular defect insertion circumstance analysis and defect prediction. The first step in such analyses is identifying defect-correcting changes in the version archive (bugfix commits) and linking them to corresponding entries in the defect database, thus establishing bugfix links, in order to enrich the content of the defect-correcting change with additional meta-data. Typically, identifying the bugfix commits in a version archive is done via heuristic string matching on the commit message. Research questions: Which filters could be used to obtain a set of bugfix links? How does one set the cutoff parameters of each? What effect (results loss and precision) does each filter then have? Which overall precision, results loss, and recall is achieved? Method: We analyze a comprehensive modular set of seven independent filters, including new ones that make use of reverse links. We describe and evaluate visual heuristics (based on simple diagnostic plots) for setting six filters' cutoff parameter. We apply these to a commercial repository from the Web CMS domain and validate the results with unprecendented precision by making use of a product expert to manually verify over 2500 links. Results: The parameter selection heuristics pick a very good parameter value in five of the six cases and a reasonably good one in the sixth. As a result, the combined filtering, called bflinks, proposes a set of bugfix links that has 93\% precision with only 7\% results loss. Conclusion: The modular filtering approach can provide high-quality results and can be adapted to repositories with different properties

Microlensing of the broad-line region in the quadruply imaged quasar HE0435-1223

Using infrared spectra of the z = 1.693 quadruply lensed quasar HE0435-1223 acquired in 2009 with the spectrograph SINFONI at the ESO Very Large Telescope, we have detected a clear microlensing effect in images A and D. While microlensing affects the blue and red wings of the H{\alpha} line profile in image D very differently, it de-magnifies the line core in image A. The combination of these different effects sets constraints on the line-emitting region; these constraints suggest that a rotating ring is at the origin of the H{\alpha} line. Visible spectra obtained in 2004 and 2012 indicate that the MgII line profile is microlensed in the same way as the H{\alpha} line. Our results therefore favour flattened geometries for the low-ionization line-emitting region, for example, a Keplerian disk. Biconical models cannot be ruled out but require more fine-tuning. Flux ratios between the different images are also derived and confirm flux anomalies with respect to estimates from lens models with smooth mass distributions.Comment: 6 pages, 4 figures, 3 tables, accepted by A&A on 10 April 201

Stokes imaging polarimetry using image restoration: A calibration strategy for Fabry-P\'{e}rot based instruments

context: The combination of image restoration and a Fabry-P\'{e}rot interferometer (FPI) based instrument in solar observations results in specific calibration issues. FPIs generally show variations over the field-of-view, while in the image restoration process, the 1-to-1 relation between pixel space and image space is lost, thus complicating any correcting for such variations. aims: We develop a data reduction method that takes these issues into account and minimizes the resulting errors. methods: By accounting for the time variations in the telescope's Mueller matrix and using separate calibration data optimized for the wavefront sensing in the MOMFBD image restoration process and for the final deconvolution of the data, we have removed most of the calibration artifacts from the resulting data. results: Using this method to reduce full Stokes data from CRISP at the SST, we find that it drastically reduces the instrumental and image restoration artifacts resulting from cavity errors, reflectivity variations, and the polarization dependence of flatfields. The results allow for useful scientific interpretation. Inversions of restored data from the $\delta$ sunspot AR11029 using the Nicole inversion code, reveal strong (~10 km/s) downflows near the disk center side of the umbra. conclusions: The use of image restoration in combination with an FPI-based instrument leads to complications in the calibrations and intrinsic limitations to the accuracy that can be achieved. We find that for CRISP, the resulting errors can be kept mostly below the polarimetric accuracy of ~10^-3. Similar instruments aiming for higher polarimetric and high spectroscopic accuracy, will, however, need to take these problems into account. keywords: Techniques: image processing, polarimetric, imaging spectroscopy, Sun: surface magnetism, sunspots, activityComment: Astronomy and Astrophysics (accepted

Alternative Lithographic Methods for Variable Aspect Ratio Vias

The foundation of semiconductor industry has historically been driven by scaling. Device size reduction is enabled by increased pattern density, enhancing functionality and effectively reducing cost per chip. Aggressive reductions in memory cell size have resulted in systems with diminishing area between parallel bit/word lines. This affords an even greater challenge in the patterning of contact level features that are inherently difficult to resolve because of their relatively small area, a product of their two domain critical dimension image. To accommodate these trends there has been a shift toward the implementation of elliptical contact features. This empowers designers to maximize the use of free space between bit/word lines and gate stacks while preserving contact area; effectively reducing the minor via axis dimension while maintaining a patternable threshold in increasingly dense circuitry. It is therefore critical to provide methods that enhance the resolving capacity of varying aspect ratio vias for implementation in electronic design systems. This work separately investigates two unique, non-traditional lithographic techniques in the integration of an optical vortex mask as well as a polymer assembly system as means to augment ellipticity while facilitating contact feature scaling. This document affords a fundamental overview of imaging theory, details previous literature as to the technological trends enabling the resolving of contact features and demonstrates simulated & empirical evidence that the described methods have great potential to extend the resolution of variable aspect ratio vias using lithographic technologies