Invited

Why teaching problem solving is a problem, at 2010 Science and Technology in Society Forum (Kyoto, Japan), Sunday, October 3, 2010:
Of all the skills that are important in life in general and science, math and engineering education I n particular, the one that is most generally considered to be the most important one is problem solving. But what is problem solving? Problem solving is the process of moving toward a goal when the path to that goal is uncertain. The traditional approach to education largely fails to teach real problem solving. What can we do to address this problem?
Black silicon: engineering an intermediate band in silicon for photovoltaic applications, at 240th National Meeting of the American Chemical Society (Boston, MA), Wednesday, August 25, 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, from highly-sensitive PIN photodetectors to photovoltaics.
Impact of Peer Instruction on underrepresented groups, at American Association of Physics Teachers Summer Meeting 2010 (Portland, OR), Monday, July 19, 2010:
This talk discusses the performance of traditionally underrepresented groups (women and underrepresented racial and ethnic minority groups) when taught introductory physics using Peer Instruction, either with traditional discussion sections or combined with other interactive engagement strategies. On average, students from these underrepresented groups enter with weaker preparation; for data obtained at Harvard University, we examine end-of-semester performance results, both end-of-semester conceptual inventory data and student grades, controlling for student background. We also summarize... Read more about Impact of Peer Instruction on underrepresented groups
Femtosecond laser micromachining of transparent materials, at Topical Meeting on Bragg Gratings, Photosensitivity and Poling in Glass Waveguides (Karlsruhe, Germany), Monday, June 21, 2010:
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, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside single cells.
Direct writing of metallic structures for metamaterial applications, at Tri-Service Metamaterials Review (Virginia Beach, VA), Wednesday, May 26, 2010:
Ultrafast-laser micromachining allows for 3D fabrication of structures much smaller than the diffraction limited laser spot size in transparent media such as glass. Under a linear regime, the media does not absorb light at the operating wavelength of the laser. However, using ultrafast pulses, we can obtain material modification through non-linear absorption. The technique can also be used to induce chemical reactions. High intensity femtosecond laser pulses can induce the photoreduction of metal ions through non-linear absorption. We use solutions containing metal salts to grow metal... Read more about Direct writing of metallic structures for metamaterial applications
Black silicon: Engineering an intermediate band in silicon for sensing and energy harvesting, at Nanophotonics and Plasmonic Technologies Workshop, Harvard University (Cambridge, MA), Friday, May 7, 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.
Optical Hyperdoping: Transforming Semiconductor Band Structure for Solar Energy Harvesting, at Third-Generation Solar Technologies Multidisciplinary Workshop: Synergistic Chemistry-Materials-Mathematical Sciences Approaches to Addressing Solar Energy Problems (San Francisco, CA), Monday, April 5, 2010:
Harvesting solar energy at the terawatt scale requires technologies that can be produced inexpensively using Earth-abundant materials. Although technologies built from Earth-abundant materials exist for converting solar energy to electrical energy or chemical energy, none are yet cost-competitive with fossil fuels. Meeting the challenge of harvesting solar energy with Earth-abundant materials such as Si and TiO2 will require transformative approaches to increase efficiency, lower manufacturing cost, and reduce material requirements. While these materials have been widely studied, we bring a... Read more about Optical Hyperdoping: Transforming Semiconductor Band Structure for Solar Energy Harvesting

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