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1999

Black silicon: A new light absorber for photovoltaic applications, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
talk_265.pdf
We demonstrate a new technique for texturing silicon surfaces using femtosecond laser pulses. Sharp micron-sized spikes are created by repeatedly irradiating a silicon surface with femtosecond laser pulses in the presence of SF6. The spikes are highly light-absorbing and enhance the light absorption in silicon close to 100 (increase in photocurrent of more than 60) over flat silicon. Spiked silicon is of potential use as a highly efficient light-absorber for solar cells and photodetectors.
Molecular orientation in Langmuir monolayers studied by surface second harmonic generation, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
talk_266.pdf
We used surface second harmonic generation (SHG) to study molecular orientation in a smectic-C liquid-crystal Langmuir monolayer at an air/water interface. The molecules under investigation are 4-octyl-4'-(3-carboxytrimenthyleneoxy) azobenzene (8AZ3). Because water is inversion symmetric, the SHG signal comes only from the surface. Furthermore, the magnitude of the surface SHG signal depends on the orientation of molecules, which makes SHG a sensitive probe of the phase of the monolayer. We measured the response of the SHG signal as we compressed the monolayer from a smectic-C phase to a more... Read more about Molecular orientation in Langmuir monolayers studied by surface second harmonic generation
Understanding or Memorization: Are we Teaching the Right Thing?, at APS Centennial Lecture, Christopher Newport University (Newport News, VA), Monday, February 22, 1999:
talk_261.pdf
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 Understanding or Memorization: Are we Teaching the Right Thing?
Understanding or Memorization: Are we Teaching the Right Thing?, at APS Centennial Lecture, College of Charleston (Charleston, SC), Friday, February 19, 1999
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 Understanding or Memorization: Are we Teaching the Right Thing?
Laser-induced microexplosions: Ultrafast physics with clinical applications, at Physics Colloquium, Texas A&M University (College Station, TX), Thursday, February 18, 1999:
talk_259.pdf
Recently there has been much interest in using femtosecond laser pulses in surgical applications. For example, femtosecond lasers could replace the nanosecond systems currently used for opthalmic photodisruption, providing improved surgical precision and adding versatility. In surgical applications, it is the high intensity of femtosecond laser pulses that is exploited. By tightly focusing these short pulses, the intensity becomes high enough to cause nonlinear absorption inside a transparent material (such as the vitreous humor). The absorption produces a hot plasma inside the sample that is... Read more about Laser-induced microexplosions: Ultrafast physics with clinical applications
Quick as a Flash: Observing Ultrafast Laser-Induced Dynamics in Semiconductors, at Condensed Matter Seminar, Texas A&M University (College Station, TX), Wednesday, February 17, 1999:
talk_258.pdf
For over two decades the subject of laser-induced phase transitions in semiconductors has generated considerable interest. This is in part because of the technological interest of semiconductors in general and the annealing of ion-implanted semiconductors in particular. Recent experiments with ultrashort laser pulses suggest that an ultrafast transformation from an ordered semiconductor to a disordered metal takes place after excitation with intense femtosecond laser pulses. Using both linear and nonlinear optical techniques we have been able to directly observe the dielectric constant of... Read more about Quick as a Flash: Observing Ultrafast Laser-Induced Dynamics in Semiconductors

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