2009

Nonlinear optics at the nanoscale: all-optical logic gates, at AP298r Research Seminar, Harvard University (Cambridge, MA), Wednesday, March 18, 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: all-optical logic gates
Confessions of a converted lecturer, at NYU-Poly (Brooklyn, NY), Wednesday, March 11, 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
Meeting the information age challenge, at AKU-FAS Core Curriculum Workshoip, Babson College (Wellesley, MA), Saturday, February 28, 2009:
The traditional approach to teaching -- lecturing -- predates medieval times and focuses solely on the transfer of information. Before the printing press, lecturing was the only way to educate the next generation. Even though information is now readily in many forms, we still largely rely on this antiquated method of teaching. Instead of lecturing, we should devote our attention to helping students assimilate information. In this talk I will discuss how the information age is reshaping the education landscape.
Turning lectures into learning, at 2009 ConnectEd Summit (Abilene, TX), Friday, February 27, 2009:
The traditional approach to teaching -- lecturing -- predates medieval times and focuses solely on the transfer of information. Before the printing press, lecturing was the only way to educate the next generation. Even though information is now readily in many forms, we still largely rely on this antiquated method of teaching. Instead of lecturing, we should devote our attention to helping students assimilate information. In this talk I will discuss and demonstrate one method, Peer Instruction, that I have successfully employed to help students assimilate conceptual knowledge in class. We... Read more about Turning lectures into learning
Subcellular surgery and nanosurgery, at Physics Seminar, Abilene Christian University (Abilene, TX), Thursday, February 26, 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
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
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
Serendipity, science, and engineering, at Sophomore forum, Harvard University (Cambridge, MA), Wednesday, February 11, 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.
Ultrafast exciton dynamics in highly excited bulk ZnO, at Photonics West 2009 (San Jose, CA), Wednesday, January 28, 2009:
Large bandgap semiconductors like ZnO are currently of interest as light emitters in the blue-UV spectral range. Advances in these technologies rely on a fundamental understanding of carrier dynamics and excitonic effects at high excitation densities. Researchers have described highly photo-excited ZnO using the polariton model. However, at high excitation, one would expect screening effects to come into play, such that the polariton model would no longer hold. With high carrier densities induced by intense, ultrashort laser pulses, we are able to monitor exciton dynamics through our micro-... Read more about Ultrafast exciton dynamics in highly excited bulk ZnO

Pages