Invited

Black silicon, at SPIE Photonics West (San Francisco, CA), Monday, January 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. 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; Using lasers to tailor the optoelectronic properties of semiconductors, at 2009 Fall MRS Meeting: Ultrafast Materials Science Symposium (Boston, MA), Wednesday, December 2, 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.
Gender, interactive teaching, and barriers to change, at Women in Science and Engineering Workshop, Thomas Jefferson National Accelerator Facility (Newport News, VA), Monday, November 16, 2009:
Can pedagogy alleviate the well-known "gender gap" in performance and representation in the physical sciences? I will show that women can succeed on par with male students in introductory classes that are taught cooperatively, rather than competitively. At the same time we found that the level of perceived confusion increases in classes that challenge every student to think about and respond to questions asked during class. This increase is a potential barrier to reform even though we have shown it to anti-correlate with performance.
Nanosurgery with Femtosecond Lasers, at 2009 OSA Frontiers in Optics (San Jose, CA), Wednesday, October 14, 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 Nanosurgery with Femtosecond Lasers
Applications of femtosecond lasers in materials processing, at Conference on Lasers and Electro-Optics Europe (Munich, Germany), Wednesday, June 17, 2009:
Chemical bonding, phase transitions, and surface processes occur on timescales comparable to the natural oscillation periods of atoms and molecules, in the range of femtoseconds (1 fs =10�15 s) to picoseconds (1 ps = 10�12 s). Advances in the generation of ultrashort laser pulses in the past two decades have made it possible to directly observe these fundamental processes. These advances have taken us from the picosecond timescale a generation ago, to the femtosecond timescale in the past decade, and recently into the attosecond (1 as = 10�18 s) regime. Materials science,... Read more about Applications of femtosecond lasers in materials processing
Femtosecond laser micromachining for applications in microphotonics, at E-MRS Meeting (Strassbourg, France), Thursday, June 11, 2009:
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.
Technology is not a pedagogy: Peer Instruction with and without clickers, at 2009 AAPT Winter Meeting (Chicago, IL), Monday, February 16, 2009:
Peer Instruction is an instructional strategy for engaging students during class using a structured questioning process. Results from a wide variety of institutions indicate that Peer Instruction increases student mastery of conceptual reasoning and quantitative problem solving and decreases attrition rates. The technique is most frequently implemented with clickers, even though flashcards or raised hands can also be used. We recently studied the effect of clickers on the implementation of Peer Instruction and found that the benefits result more from the pedagogy than from the clicker... Read more about Technology is not a pedagogy: Peer Instruction with and without clickers
Disseminating Curriculum and Pedagogy: Peer Instruction, at Joint AAPT/AAAS 2009 Annual Winter Meeting (Chicago, IL), Saturday, February 14, 2009:
I coined the term "Peer Instruction" (and the associated "ConcepTests") to describe a technique I was starting to implement in my class in an NSF proposal I wrote 1991. I implemented the technique to solve a problem in my own class, never anticipating the wide acceptance the technique (and the terms) would find over the course of the next decade and a half. The technique has found a broad following across disciplines, across institutions, and across the world, even if some adaptations stray far from my original ideas. What is it that accounts for the method's rapid dissemination? Does the... Read more about Disseminating Curriculum and Pedagogy: Peer Instruction
Optically hyperdoped silicon, at The 39th Winter Colloquium on the Physics of Quantum Electronics (Snowbird, UT), Thursday, January 8, 2009:
By irradiating silicon with a train of femtosecond laser pulses in the presence of chalcogen (column VI) compounds, a thin layer of Si is doped to previously unreported, non-equilibrium levels (about 2%). This optical hyperdoping (OHD) process creates a highly absorbing surface and extends silicon’s spectral sensitivity, even for infrared photons with energy less than the band gap. The optoelectronic properties of this 'black silicon' make it useful for a wide range of commercial devices in communications, remote sensing, and solar energy harvesting. Prototype OHD silicon photodiodes exhibit... Read more about Optically hyperdoped silicon

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