Fabrication of waveguide spatial light modulators via femtosecond laser micromachining

We have previously introduced an anisotropic leaky-mode modulator as a waveguide-based, acousto-optic solution for spatial light modulation in holographic video display systems. Waveguide fabrication for these and similar surface acoustic wave devices relies on proton exchange of a lithium niobate substrate, which involves the immersion of the substrate in an acid melt. While simple and effective, waveguide depth and index profiles resulting from proton exchange are often non-uniform over the device length or inconsistent between waveguides fabricated at different times using the same melt and annealing parameters. In contrast to proton exchange, direct writing of waveguides has the appeal of simplifying fabrication (as these methods are inherently maskless) and the potential of fine and consistent control over waveguide depth and index profiles. In this paper, we explore femtosecond laser micromachining as an alternative to proton exchange in the fabrication of waveguides for anisotropic leaky-mode modulators

Progress in off-plane computer-generated waveguide holography for near-to-eye 3D display

Waveguide holography refers to the use of holographic techniques for the control of guided-wave light in integrated optical devices (e.g., off-plane grating couplers and in-plane distributed Bragg gratings for guided-wave optical filtering). Off-plane computer-generated waveguide holography (CGWH) has also been employed in the generation of simple field distributions for image display. We have previously depicted the design and fabrication of a binary-phase CGWH operating in the Raman-Nath regime for the purposes of near-to-eye 3-D display and as a precursor to a dynamic, transparent flat-panel guided-wave holographic video display. In this paper, we describe design algorithms and fabrication techniques for multilevel phase CGWHs for near-to-eye 3-D display

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

BACKGROUND:Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed. METHODOLOGY/PRINCIPAL FINDINGS:Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide), a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major) via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN). PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB. CONCLUSIONS:Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Towards a shared language of the meaning of materials

Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2016.Cataloged from PDF version of thesis.Includes bibliographical references (pages 193-200).Due to advances in design generation and digital fabrication, novice designers are able to access more and more tools to bring their visions to life. As materials begin to evolve and change shape, having a set of rules with which to evaluate, interpret, and design them will become increasingly important. In moving towards tools that allow us to design and create our own materials these the two worlds of creation and curation must be (re)connected: in this work I strive to quantify and understand the emotive aspects of materials, such as haptic responses to, cognitive evaluation of, and emotive perception of materials; in order to understand how materials communicate meaning. My aim is to produce a set of guidelines that enable designers and scientists to communicate and help creators understand the implications of emerging material combinations. For those without the resources to conduct time intensive user studies for every project and without the intuitive knowledge of a professional, it can be very difficult to predict the implications of materials and their impact on the interaction. In this thesis, a repeatable methodology for exploring these impacts was implemented and evaluated. As a result, it will be possible to create a holistic material selection process. By combining materials to maximize properties, I plan to go beyond existing databases and fabricate objects designed to evoke specific reactions. Developing an effective methodology would enable fabrication of more engaging objects. Through this research, I plan to establish guidelines and provide a common language that enables designers to influence materials development and connect designers and researchers in a more effective way than is currently possible. This will promote unique research of materials and expand their range of use. Such a tool will enable new design practices by adding emotive factors that are not rigorously understood to the material selection and fabrication process. At its core, materials science is the study of how the structure and processing of materials impact the properties of compounds. I plan to help designers and scientists go one step further, and use material combinations to connect directly with the end user.by Bianca C. Datta.S.M

Biologically-inspired Structural Color: Material Design and Fabrication Strategies Drawn from Nature’s Color Palette

To harness the spectacular functionality found in nature, researchers have developed a multitude of biomimetic and bio-inspired techniques, each with strengths and constraints. A classic example is structural color, which abounds in nature, creating captivating visual displays from the brilliant plumage of the bird of paradise to the camouflage of the chameleon, with functional uses in mating, warning, communication, defense and more. Structural color provides a fascinating case study for exploring the role of material design on macroscale properties and can provide insights on animal evolution, photonic devices, human and animal communication, signaling, and art. These impressive effects result from interference and diffraction of light incident upon multilayer nanostructures, in which color is broadly tuned based on surface structure and geometry. Throughout the natural world, we see examples of clever, multifunctional features and solutions adapted to serve organisms in their local environments, interact with other living creatures, and maintain robustness and structural integrity over a lifetime. The processes and resulting hierarchical systems use few materials and demonstrate complex functional properties that inspire human-made engineered systems. This thesis provides tools and design methodologies for directing design and fabrication of structurally-colored surfaces. First, we depict methodologies based around computational inverse design for the formulation of nanostructures exhibiting structural col-oration, and demonstrate prototype surfaces fabricated from these designs. Next, we employ self-assembly of colloidal particles as a versatile, low cost approach for mimicking aspects of natural coloration. We explore the role of substrates on evaporative dynamics and interplay between pigment and structure in pattern formation. We further examine the social implications of such work; as commercialization of structural color becomes more feasible, we have an opportunity to critically examine the social and environmental impacts and contributions of this ˝eld. Through this work, we aim to provide methods and tools for researchers to control color production and devise new structurally-colored surfaces with directed properties by presenting material building blocks and demonstrating their role in color production. This thesis provides a path towards expanding the palette of achievable colors and pat-terns through bio-inspired design techniques, and lends an understanding of the multitude of ways in which we can pattern, tune, and control factors that induce coloration. The benefits of such biomimetic nanostructures are plentiful: they provide brilliant, iridescent color with mechanical stability and light steering capabilities. Structural color can be harnessed for long lasting paints, fabrics, signaling and communication systems, and displays. The color changes achievable with these structures are intuitively interpretable by humans. We discuss the methods for control over material design to tune nano- and microscale structure and properties in order to achieve macro scale responses that humans can interact with in meaningful and interesting ways. Through this work, we aim to provide tools with which researchers can explore color through a material design lens.Ph.D