Presentations

    Wrapping light around a hair, at Physics Colloquium, McGill University (Montreal, Canada), Thursday, January 17, 2008:
    Can light be guided by a fiber whose diameter is much smaller than the wavelength of the light? Can we mold the flow of light on the micrometer scale so it wraps, say, around a hair? Until recently the answer to these questions was ‘no’. We developed a technique for drawing long, free-standing silica wires with diameters down to 50 nm that have a surface smoothness at the atomic level and a high uniformity of diameter. Light can be launched into these silica nanowires by optical evanescent coupling and the wires allow low-loss single-mode operation. They can be bent sharply, making it... Read more about Wrapping light around a hair
    Nonlinear optics at the nanoscale, at Physics Colloquium, University of Massachusetts Lowell (Lowell, MA), Wednesday, February 13, 2008:
    We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
    Wrapping light around a hair, at Physics Colloquium, Pomona College (Claremont, CA), Tuesday, April 15, 2008:
    Can light be guided by a fiber whose diameter is much smaller than the wavelength of the light? Can we mold the flow of light on the micrometer scale so it wraps, say, around a hair? Until recently the answer to these questions was ‘no’. We developed a technique for drawing long, free-standing silica wires with diameters down to 50 nm that have a surface smoothness at the atomic level and a high uniformity of diameter. Light can be launched into these silica nanowires by optical evanescent coupling and the wires allow low-loss single-mode operation. They can be bent sharply, making it... Read more about Wrapping light around a hair
    The scientific approach to teaching: Research as a basis for course design, at Physics Colloquium, University of Iowa (Iowa City, IA), Monday, September 8, 2008:
    Discussions of teaching -- even some publications -- abound with anecdotal evidence. Our intuition often supplants a systematic, scientific approach to finding out what works and what doesn't work. Yet, research is increasingly demonstrating that our gut feelings about teaching are often wrong. In this talk I will discuss some research my group has done on gender issues in science courses and on the effectiveness of classroom demonstrations.
    Extending silicon's reach: nonequlibrium doping using ultrafast lasers, at Physics Colloquium, University of Massachusetts, Lowell (Lowell, MA), Wednesday, October 22, 2008:
    Silicon is the world's widely used semiconductor. As the building block of a photovoltaic cell, silicon offers the best combination of stability, efficiency, and manufacturability. However, as an indirect absorber of light, thick layers of highly-pure, expensive material are required for efficient light absorption and charge collection. Furthermore, silicon does not absorb in the infrared, a spectral region that contains about a quarter of the sun's radiation. In this talk, I will discuss non-equilibrium laser-doping techniques we have been developing in the Mazur group that attempt to... Read more about Extending silicon's reach: nonequlibrium doping using ultrafast lasers
    Femtosecond laser interactions with materials: from micromachining to microsurgery, at Materials Science and Engineering Colloquium, Stanford University (Palo Alto, CA), Friday, October 31, 2008:
    When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, and fabrication of micromechanical devices in polymers.

    We have used this technique to manipulate sub-cellular structures inside live and fixed cells. Using...

    Read more about Femtosecond laser interactions with materials: from micromachining to microsurgery
    Subcellular surgery and nanosurgery, at Physics Colloquium, University of Massachusetts Boston (Boston, MA), Wednesday, November 5, 2008:
    We use femtosecond laser pulses to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We have also used the technique to micromanipulate the neural network of C. Elegans, a small nematode. Our laser scalpel can snip individual axons without causing any damage to surrounding tissue, allowing us to study the function of individual... Read more about Subcellular surgery and nanosurgery
    Optical hyperdoping: Extending silicon's reach, at Jones Seminar, Thayer School of Engineering, Dartmouth University (Hanover, NH), Friday, February 13, 2009:
    Silicon is the world's most widely used semiconductor. As the building block of a photovoltaic cell, silicon offers a combination of stability, efficiency, and manufacturability currently unmatched by any other material. However, as an indirect absorber of light, thick layers of highly-pure, expensive material are required for efficient light absorption and charge collection. Furthermore, silicon does not absorb in the infrared, a spectral region that contains about a quarter of the sun's radiation. In this talk, I will discuss optical hyperdoping, a non-equilibrium laser-doping technique we... Read more about Optical hyperdoping: Extending silicon's reach
    Subcellular surgery and nanosurgery, at Physics Colloquium, Australian National University (Canberra, Australia), Tuesday, March 24, 2009:
    We use femtosecond laser pulses to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We have also used the technique to micromanipulate the neural network of C. Elegans, a small nematode. Our laser scalpel can snip individual axons without causing any damage to surrounding tissue, allowing us to study the function of individual... Read more about Subcellular surgery and nanosurgery
    Confessions of a converted lecturer, at Physics Colloquium, University of North Carolina at Chapel Hill (Chapel Hill, NC), Monday, April 6, 2009:
    I thought I was a good teacher until I discovered my students were just memorizing information rather than learning to understand the material. Who was to blame? The students? The material? I will explain how I came to the agonizing conclusion that the culprit was neither of these. It was my teaching that caused students to fail! I will show how I have adjusted my approach to teaching and how it has improved my students' performance significantly
    Nonlinear optics at the nanoscale, at Physics Colloquium, Boston College (Chestnut Hill, MA), Wednesday, April 8, 2009:
    We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
    The make-believe world of real-world physics, at Physics Colloquium, Brandeis University (Waltham, MA), Tuesday, September 8, 2009:
    That physics describes the real world is a given for physicists. In spite of tireless efforts by instructors to connect physics to the real world, students walk away from physics courses believing physicists live in a world of their own. Are students clueless about the real world? Or are we perhaps deluding ourselves and misleading our students about the real world?
    Nonlinear optics at the nanoscale, at Physics Colloquium, Temple University (Philadelphia, PA), Monday, September 21, 2009:
    We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
    Confessions of a converted lecturer, at Physics Colloquium, Harvard University (Cambridge, MA), Monday, September 28, 2009:
    I thought I was a good teacher until I discovered my students were just memorizing information rather than learning to understand the material. Who was to blame? The students? The material? I will explain how I came to the agonizing conclusion that the culprit was neither of these. It was my teaching that caused students to fail! I will show how I have adjusted my approach to teaching and how it has improved my students' performance significantly
    Optical Hyperdoping: Silicon sees the infrared light, at Applied Physics Colloquium, Harvard University (Cambridge, MA), Friday, October 9, 2009:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Venturing toward better teaching: Professors' knowledge base for pedagogical improvement in introductory STEM classrooms at major research universities., at The Association for The Study of Higher Education Annual Meeting (Vancouver, BC, Canada), Thursday, November 5, 2009
    Educational reformers often portray the majority of science, technology, engineering and mathematics (STEM) professors at American research universities as subject-matter experts but pedagogical novices (Baldwin, 2009; Boyer, 1998; Coopala, 2009; Handeslman et al., 2006; Wieman, 2006). Images of STEM professors as lacking knowledge about best teaching practices are especially prevalent in discussions about academic researchers: A wide array of constituents, from students and journalists to scholars of teaching and learning, have long proffered views of academic researchers as so heavily... Read more about Venturing toward better teaching: Professors' knowledge base for pedagogical improvement in introductory STEM classrooms at major research universities.
    Nonlinear optics at the nanoscale, at Physics Colloquium, University of Maryland Baltimore County (Baltimore, MD), Wednesday, November 11, 2009:
    We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ), making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that... Read more about Nonlinear optics at the nanoscale
    Black silicon, at University of Queensland (Brisbane, Australia), Friday, January 15, 2010:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer drastically changes the optical, material and electronic properties of the wafer. The resulting textured surface is highly absorbing and looks black to the eye. The properties of this 'black silicon' make it useful for a wide range of commercial devices. In particular, we have been able to fabricate highly-sensitive PIN photodetectors using this material. The sensitivity extends to wavelengths of 1600 nm making them particularly useful for applications in communications and remote sensing.
    Subcellular surgery and nanosurgery, at Physics Colloquium, Clark University (Worcester, MA), Wednesday, April 7, 2010:
    We use femtosecond laser pulses to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We have also used the technique to micromanipulate the neural network of C. Elegans, a small nematode. Our laser scalpel can snip individual axons without causing any damage to surrounding tissue, allowing us to study the function of individual... Read more about Subcellular surgery and nanosurgery
    Subcellular surgery and nanosurgery, at Physics Colloquium, University of Notre Dame (Notre Dame, IN), Wednesday, May 12, 2010:
    We use femtosecond laser pulses to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We have also used the technique to micromanipulate the neural network of C. Elegans, a small nematode. Our laser scalpel can snip individual axons without causing any damage to surrounding tissue, allowing us to study the function of individual... Read more about Subcellular surgery and nanosurgery

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