Presentations

    2D impedance-matched zero-index metamaterial, at SPIE Photonics West: Photonic and Phononic Properties of Engineered Nanostructures IV (San Francisco, California), Wednesday, February 5, 2014
    Recent efforts to achieve metamaterials with a vanishing refractive index take advantage of the low index at a photonic band edge. This behavior is accompanied by a divergent impedance, resulting in inefficient transmission. We investigate the nature of this discontinuity and show that it can be removed by tuning the electric and magnetic response of the metamaterial. We present a design for a 2D zero-index metamaterial based on this concept. The metamaterial is entirely dielectric, which results in low-loss transmission at the design wavelength of 1.55um. This behavior is confirmed using... Read more about 2D impedance-matched zero-index metamaterial
    Assessing the initial state of knowledge of first-year genetics students, at ASM Eighth Undergraduate Microbiology Education Conference, American Society for Microbiology (Orlando, FL), Saturday, May 19, 2001:
    A survey was designed to assess students' understanding of concepts and familiarity with biology terminology at the beginning of a new introductory genetics course. The class, which serves as the first college biology course for all students majoring in Biological Sciences or fulfilling premedical requirements, assumes no prior knowledge and enrolls mainly first-year students. The survey asked students to rate their familiarity with over 80 words in genetics and to define a selection of these terms. Students were also asked to answer a few conceptual questions as well as provide background... Read more about Assessing the initial state of knowledge of first-year genetics students
    Knowing as the Stage for Doing: Developing Professors’ Pedagogical Knowledge, Attitudes, Practice, and Dissemination During Cross-­‐national Faculty Development Programs, at American Education Research Association Annual Meeting (Vancouver, BC, Canada), Saturday, April 14, 2012:
    This poster will present the findings of a case study research project designed around an innovative approach to faculty development in Latin America and the Caribbean. The project trained over 75 professors from research universities in Chile,Costa Rica, and the Dominican Republic. The program currently measures four dimensions of pedagogical change: knowledge, attitudes, practice and dissemination. We will solicit feedback on our faculty development and program assessment model so that we may further improve our ability to potentiate pedagogical change in Latin American higher education and... Read more about Knowing as the Stage for Doing: Developing Professors’ Pedagogical Knowledge, Attitudes, Practice, and Dissemination During Cross-­‐national Faculty Development Programs
    Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics, at MRS 2014 Fall Meeting and Exhibit, Symposium L: Optical Metamaterials and Novel Optical Phenomena Based on Nanofabricated Structures (Boston, MA), Thursday, December 4, 2014
    Integrated diffractive optics has many applications in beam shaping and control on the micro-scale. Fabrication using lithography is limited to planar or layered geometries. We demonstrate fabrication of diffractive elements via direct laser writing. We have tested 3D diffraction gratings and zone plates designed for operation at visible wavelengths. Direct laser writing is a promising technique to fabricate integrated 3D and multi-layer diffraction optics. We have previously developed a laser writing technique that enables fabrication of disconnected metal structures in a polymer matrix,... Read more about Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics
    Femtosecond laser micromachining of bulk glass at oscillator energies, at Gordon Conference on Nonlinear Optics, Colby Sawyer College (New London, NH), Tuesday, July 27, 1999:
    Using femtosecond laser pulses generated by a 25-MHz Ti:Sapphire laser oscillator, we micromachine bulk glass. The laser is focused by a 1.4 numerical aperture microscope objective, allowing the breakdown threshold to be reached with modest energies (4.5 nJ). Single-shot damage is sub-micron in size. Because the pulses arrive faster than energy can diffuse out of the focal volume, multiple shot damage with this laser is thermal in nature. Successive pulses add more and more heat to the sample, melting a micron-sized volume. Using this thermal machining, we have written single-mode waveguides... Read more about Femtosecond laser micromachining of bulk glass at oscillator energies
    Transition from repetitive to cumulative thermal processing in femtosecond laser induced machining of embedded waveguides, at Photonics West (San Jose, California), Saturday, January 25, 2003:
    In previous work, we have demonstrated laser writing of embedded waveguides in silicate glasses with only nanojoules of energy. The laser system is an unamplified 25 MHz laser oscillator generating 24-nJ, 55-fs pulses. Laser machining at this high repetition rate results in a cumulative thermal mechanism of material modification which leads to structural index of refraction changes beyond the focal volume. We present a parametric study of the role of the laser repetition rate in the size of the machined structures. The material used for the study is a chalcogenide glass, As_2S_3. We identify... Read more about Transition from repetitive to cumulative thermal processing in femtosecond laser induced machining of embedded waveguides
    Optical waveguide wiring using femtosecond laser pulses between multiple pieces of glass for optical sensor applications, at 2005 SPIE Photonics West Conference, Program on Laser Micro-/Nanoengineering and applications, Commercial and Biomedical Applications of Ultrafast Lasers VI (San Jose, CA), Tuesday, January 25, 2005:
    We demonstrate optical waveguide wiring between multiple pieces of glass using high-repetition rate femtosecond laser pulses focused with a 1.4 NA oil-immersion microscope objective. In conventional waveguide wiring techniques, connecting optical waveguides in different pieces of glass requires special attention because of the very small core size of the waveguides. Connecting waveguides therefore necessitates highly accurate positioning stages and is a time consuming process. We demonstrate that it is possible to write optical waveguides across the gap between two pieces of glass with a... Read more about Optical waveguide wiring using femtosecond laser pulses between multiple pieces of glass for optical sensor applications
    Complex microstructures fabricated via two-photon absorption polymerization, at Macro 2006 - 41st Inernational Symposium on Macromolecules (Rio de Janeiro, RG, Brazil), Sunday, July 16, 2006:
    Using acrylic resin and Lucirin TPO-L as photoinitiator, we fabricated complex microstructures via the process of two photon absorption (2PA) polymerization. We measured the 2PA cross-section of Lucirin TPO-L, which is the parameter responsible for the nonlinear process, and the value found is among the ones reported in the literature for common photoinitiators. We also carried out quantum chemistry calculation in order to correlate the nonlinear optical properties of this photoinitiator to its molecular structure.
    Femtosecond laser micromachining in azopolymer films, at 2006 MRS Fall Meeting (Boston, MA, USA), Monday, November 27, 2006:
    In this work, we investigated femtosecond laser micromachining in both poly(methyl methacrylate) (PMMA) and PMMA doped with the azoaromatic compounds Disperse Red 1 (DR1) and Disperse Red 13 (DR13). These compounds are particularly interesting due to their linear and nonlinear optical properties.
    Three-dimensional microfabrication with conjugated polymers, at 2006 MRS Fall Meetng (Boston, MA, USA), Thursday, November 30, 2006:
    In this work we present new resin formulations containing active components, that can be polymerized by two-photon absorption in order to fabricate microstructures. The host resin we used consists of tris(2-hydroxyethyl)isocyanurate triacrylate, which gives hardness to the polymeric structure, ethoxylated(6) trimethyl-lolpropane triacrylate, which assists in decreasing the structure shrinkage upon polymerization, and ethyl-2,4,6-trimethylbenzoylphenylphosphinate, which acts as the polymerization photoinitiator. As guest material we used the conjugated polymer MEH-PPV, whose interesting... Read more about Three-dimensional microfabrication with conjugated polymers
    Femtosecond laser micromaching in the conjugated polymer MEH-PPV, at E-MRS Spring Meeting (Strasbourg, France), Thursday, May 31, 2007:
    Femtosecond-laser micromachining of poly[2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) films is investigated using 130-fs pulses at 800-nm from a laser oscillator operating at 76-MHz repetition rate. We investigate the effect of pulse energy and translation speed on the depth and morphology of the micromachined regions. We quantified the MEH-PPV photobleaching induced by the fs-laser, and the conditions in which the emission of MEH-PPV is preserved after the micromaching.
    Hydrogenated amorphous silicon laser micromachining for photonic devices, at SPIE Photonics West 2013, Synthesis and Photonics of Nanoscale Materials X (San Francisco, CA), Tuesday, February 5, 2013
    Abstract Development of integrated photonic devices is becoming increasingly important in technological applications. Hydrogenated amorphous silicon (a-Si:H) provides a promising platform. Variations in hydrogen content produce large changes in refractive index and band gap, on the order of 0.1-1. Previous research has demonstrated waveguide fabrication using photolithography and ion implantation techniques, which requires many steps and is limited to 2D patterns. We have developed a laser micromachining technique to locally reduce the hydrogen content of a-Si:H in the laser focus to... Read more about Hydrogenated amorphous silicon laser micromachining for photonic devices

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