Colloquium

Wrapping light around a hair, at Condensed Matter and Applied Physics Colloquium, Harvard University (Cambridge, MA), Friday, May 7, 2004:
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 very uniform 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 possible to... Read more about Wrapping light around a hair
Controlling coherent optical phonons in tellurium, at JILA Colloquium, University of Colorado (Boulder, CO), Tuesday, April 20, 2004:
Using time-resolved reflectometry we measure the dielectric function of tellurium following excitation with a femtosecond laser pulse. The dielectric function reveals the ultrafast dynamics of coherent phonons in Te. Oscillations in the bonding-antibonding splitting allow for THz modulation of a semiconductor-semimetal transition. Using two-pulse sequences, we can control the phonons, stabilizing the bandstructure in the semimetallic state.
Femtosecond Laser Micromachining: Applications in Technology and Biology, at Joint University of Pittsburgh and Carnegie Mellon University Colloquium, Carnegie Mellon University (Pittsburgh, PA), Monday, April 5, 2004:
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. In this talk we will review recent results obtained in... Read more about Femtosecond Laser Micromachining: Applications in Technology and Biology
Memorization or understanding: Are we teaching the right thing?, at Physics and Astronomy Colloquium, Michigan State University (East Lansing, MI), Thursday, March 18, 2004:
Education is more than just transfer of information, yet that is what is mostly done in large introductory courses -- instructors present material (even though this material might be readily available in printed form) and for students the main purpose of lectures is to take down as many notes as they can. Few students have the ability, motivation, and discipline to synthesize all the information delivered to them. Yet synthesis is perhaps the most important -- and most elusive -- aspect of education. Students get frustrated because they are unable to grasp simple concepts. Instructors get... Read more about Memorization or understanding: Are we teaching the right thing?
Femtosecond laser-assisted microstructuring of silicon surfaces for novel detector, sensing, and display technologies, at Physics Colloquium, University of Massachusetts Lowell (Lowell, MA), Wednesday, March 10, 2004:
Irridiating silicon surfaces with trains of ultrashort laser pulses in the presence of a sulfur containing gas drastically changes the structure and properties of silicon. The normally smooth and highly reflective surface develops a forest of sharp microscopic spikes. The microstructured surface is highly absorbing even at wavelengths beyond the bandgap of silicon and has many interesting novel applications.
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.
Manipulating matter with light, at Physics Colloquium, University of Missouri-Columbia (Columbia, MO), Thursday, February 26, 2004:
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. In this talk we will review recent results obtained in... Read more about Manipulating matter with light
Interactive Learning Toolkit: Tools for the Interactive Classroom, at Invited Talk, University of Limerick (Co. Limerick, Ireland), Wednesday, December 17, 2003:
Research-based interactive learning techniques have dramatically improved student understanding. We have created the 'Interactive Learning Toolkit' (ILT), a web-based learning management system, to help implement two such pedagogies: Just in Time Teaching and Peer Instruction. Our main goal in developing this toolkit is to save the instructor time and effort and to use technology to facilitate the interaction between the students and the instructor (and between themselves). After a brief review of both pedagogies, I will demonstrate the many new exciting features of the ILT. I will show how... Read more about Interactive Learning Toolkit: Tools for the Interactive Classroom

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