Presentations

    Teaching and Research: Inseparable responsibilities of the modern physicist, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
    Mention the word ""physics"" to the average high-school student and you are not likely to see many happy faces. Public opinion of science in general--and physics in particular--is not high. More importantly, misunderstandings about the goals and procedures of physics are rampant. In part, these problems arise because physics education has focused nearly exclusively on generating a steady supply of future physicists. The need to educate non-majors, let alone the public at large, has generally not been perceived as an important mission of physics departments. Now that the need for physics is no... Read more about Teaching and Research: Inseparable responsibilities of the modern physicist
    Factors affecting gender disparity in introductory physics, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
    In America, the disparity between the performance of women and men in physics is a matter of common concern; however, it is poorly understood. Is this disparity observed among physics majors at elite institutions as well as non-majors in one-year introductory courses? Does this disparity depend on the pedagogical approach used to teach the class? The high school physics or mathematics background of the students? The gender of the instructor?
    Gender, Educational Reform, and Instructional Assessment: Part II, at Winter Meeting, American Association of Physics Teachers (Philadelphia, PA), Tuesday, January 22, 2002:
    Will current educational reform efforts serve to improve the learning experience of women in physics? To do so, assessment of instructional effectiveness must examine results for male and female students separately as well as for the entire class . We present an analysis of gender differences in performance in introductory physics at eight different colleges and universities; half of the courses were taught using a variety of interactive-engagement methods and half were taught with traditional lectures. We examine the effect of pedagogy and class size on the gender gap in both Force Concept... Read more about Gender, Educational Reform, and Instructional Assessment: Part II
    Gender and student achievement with Peer Instruction, at Physics Education Research Conference, AAPT Summer Meeting, University of Alberta (Edmonton, Alberta, Canada), Thursday, July 24, 2008:
    We investigated the effect of physics education research-based teaching methods on the gender gap in conceptual understanding in introductory physics. We analyzed data from the introductory calculus-based mechanics course for non-majors at Harvard University taught traditionally and taught with different degrees of interactive engagement. On average, female students have lower Force Concept Inventory (FCI) pretest scores than males. Teaching with Peer Instruction not only yields significantly greater FCI posttest scores for both males and females but also reduces the FCI posttest gender gap.... Read more about Gender and student achievement with Peer Instruction
    Black silicon: Microstructuring silicon with femtosecond lasers, at Physics Colloquium, University of Massachusetts-Lowell (Lowell, MA), Wednesday, November 14, 2001:
    Our research group has produced a novel form of microstructured silicon ("black silicon") with many surprising properties: near unity absorption, even below the band gap; production of photoelectrons in the visible and infrared; visible luminescence; and a strong field emission current. This talk will describe these properties and what is understood so far about their structural and chemical origin.
    Femtosecond laser-structured silicon: properties and structure, at Gordon Conference on Laser Interactions With Materials (Andover, NH), Tuesday, July 23, 2002:
    Silicon surfaces that are microstructured with femtosecond laser pulses in a sulfur hexafluoride environment exhibit several remarkable properties, including near-unity below-band gap optical absorption (C. Wu et al., Appl. Phys. Lett. 78, 1850 (2001)). We report new structural and chemical characterization of this material, including cross-sectional TEM images of the microstructures. Our results indicate that the below-band gap absorption most likely comes from a surface layer of polycrystalline silicon roughly 1 micrometer thick, which includes nanopores, nanocrystals, and a high... Read more about Femtosecond laser-structured silicon: properties and structure
    Black silicon: Changing structure and properties with light, at Physics colloquium, Clark University (Worcester, MA), Thursday, December 12, 2002:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer changes its structure and properties dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. This microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. This talk will describe the properties of this microstructured surface and discuss why the microspikes form and what is responsible for the change in optical properties.
    Black silicon: using lasers to make novel materials, at Condensed Matter Physics Seminar, Harvard University (Cambridge, MA), Friday, February 14, 2003:
    Irradiating the surface of a crystalline silicon wafer with intense laser pulses in a reactive gas environment changes the structure and properties of the wafer dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. In addition to changing the surface morphology, this microstructuring process also dramatically alters the optical properties of the silicon. The microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. We find that the laser structuring process incorporates high... Read more about Black silicon: using lasers to make novel materials
    Black silicon: changing structure and properties with light, at Physics Colloquium, Haverford College (Haverford, PA), Monday, March 1, 2004:
    Shining intense, ultrashort laser pulses on the surface of a crystalline silicon wafer changes its structure and properties dramatically: the formerly smooth, highly reflective surface becomes covered with a forest of sharp microspikes. This microstructured surface is highly absorbing even at wavelengths to which the original wafer is transparent. This talk will describe the properties of this microstructured surface and discuss why the microspikes form and what is responsible for the change in optical properties.
    Classroom Demonstrations: Learning Tools or Entertainment?, at Biennial Conference on Chemical Education, Purdue University (West Lafayette, IN), Wednesday, August 2, 2006:
    Classroom science demonstrations are intended to serve two important purposes: to increase students' interest in the material being covered and to improve students' understanding of the underlying scientific concepts. Student end-of-semester evaluations typically praise demonstrations as one of the most interesting parts of a course, suggesting that demonstrations accomplish the first objective. What about the second? Do demonstrations effectively help students learn the underlying concepts? We examined whether the mode of presentation of demonstrations affects their effectiveness as teaching... Read more about Classroom Demonstrations: Learning Tools or Entertainment?
    Early stages of femtosecond laser-induced formation of silicon microspikes, at Materials Research Society Fall Meeting (Boston, MA), Monday, December 2, 2002:
    Arrays of sharp conical spikes form on crystalline silicon surfaces when irradiated with a train of femtosecond laser pulses in a background of sulfur hexafluoride (SF6); blunter, more irregular microstructures form in vacuum. The tips of the spikes are at the height of the original surface of the wafer, suggesting that the formation process predominantly involves removing material. The spikes are arranged in a quasi-ordered fashion with a characteristic nearest-neighbor separation of a few micrometers; the exact value of this characteristic separation depends on the laser fluence and number... Read more about Early stages of femtosecond laser-induced formation of silicon microspikes
    Peer Instruction: Turning a lecture into a seminar, at Physics Colloquium, University of California San Diego (San Diego, CA), Thursday, May 6, 1999:
    Education is more than just transfer of information, yet that is mostly what happens in large introductory courses - instructors present material (even though this material might be readily available in printed form) and students take down as many notes as they can. This format tends to reinforce the idea that learning is about acquiring information rather than gaining new ways of thinking. In fields such as physics, in which learning consists primarily of developing new thinking skills, this is disastrous. Students get frustrated because their study strategies are inappropriate, and thus... Read more about Peer Instruction: Turning a lecture into a seminar
    Promise and pitfalls of reformed instruction for female students, part II, at Physics Teacher Education Coalition 2007 Conference, American Physical Society PTEC (Boulder, CO), Saturday, March 3, 2007:
    In this workshop, we will examine how reformed instruction can both help and potentially hinder female students, depending on exactly how it is implemented. In the first segment of the workshop, the workshop leaders will review pertinent research on the origins of the underrepresentation of women in the physical sciences and factors promoting the success of female students in science and mathematics classrooms. In the second portion of this workshop, participants will discuss how to structure learning in their classrooms based on insights from existing research, and will also identify... Read more about Promise and pitfalls of reformed instruction for female students, part II
    Reducing the gender gap in introductory physics, at American Physical Society March meeting (Denver, CO), Monday, March 5, 2007:
    We investigated whether the gender gap in conceptual understanding in an introductory university physics course can be reduced by teaching with interactive engagement methods that promote in-class interaction, reduce competition, foster collaboration, and emphasize conceptual understanding. To this end, we analyzed data from the introductory calculus-based physics course for non-majors at Harvard University taught traditionally or using different degrees of interactive engagement. Our results show that teaching with certain interactive strategies not only yields significantly increased... Read more about Reducing the gender gap in introductory physics