Memorization or understanding: Are we teaching the right thing?, at Physics Colloquium, UCLA (Los Angeles, CA), Thursday, March 13, 2003:
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 Micromachining: Applications in Photonics and Biology, at Modern Optics and Spectroscopy Seminar, MIT (Cambridge, MA), Tuesday, March 11, 2003:
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 living cells. In this talk I will review recent results obtained in the... Read more about Femtosecond Laser Micromachining: Applications in Photonics and Biology
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
An introduction to femtosecond laser science, at 2003 Photonics West Conference (San Jose, CA), Tuesday, January 28, 2003:
Description: This interactively taught half-day course provides basic knowledge of measurements of and research with femtosecond laser pulses. Beginning with the basic principles of the interaction of light and matter, we?ll discuss the often non-standard aspects of the interaction of intense short pulses with matter. Using worksheets we?ll address a number of common conceptual misconceptions in an interactive and collaborative setting.

Learning outcomes: This course will enable you to

  • understand the basis for the electronic and optical properties of...
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Transition from repetitive to cumulative thermal processing in femtosecond laser induced machining of embedded waveguides, at Photonics West (San Jose, California), Saturday, January 25, 2003:
In previous work, we have demonstrated laser writing of embedded waveguides in silicate glasses with only nanojoules of energy. The laser system is an unamplified 25 MHz laser oscillator generating 24-nJ, 55-fs pulses. Laser machining at this high repetition rate results in a cumulative thermal mechanism of material modification which leads to structural index of refraction changes beyond the focal volume. We present a parametric study of the role of the laser repetition rate in the size of the machined structures. The material used for the study is a chalcogenide glass, As_2S_3. We identify... Read more about Transition from repetitive to cumulative thermal processing in femtosecond laser induced machining of embedded waveguides
Ultrafast Lattice-Bonding Dynamics of Tellurium, at Ultrafast Electronics and Optoelectronics 2003 Conference (Washington, DC), Wednesday, January 15, 2003:
A pump-probe technique measuring the dielectric function is presented and applied to the ultrafast dynamics of coherent phonons in Te. Oscillations in the bonding-antibonding splitting are revealed, allowing for THz modulation of a semiconductor-semimetal transition.