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2002

Black silicon: Changing structure and properties with light, at Physics colloquium, Clark University (Worcester, MA), Thursday, December 12, 2002:
talk_449.pdf
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.
Comparing properties of femtosecond and nanosecond laser-structured silicon, at Materials Research Society Fall Meeting (Boston, MA), Monday, December 2, 2002:
talk_451.pdf
Sharp microcones form on crystalline silicon surfaces upon irradiation with either femtosecond or nanosecond laser pulses in a sulfur hexafluoride environment. While the general shape and aspect ratio of femtosecond and nanosecond laser cones are similar, several features (such as size and position relative to the original surface) suggest that different mechanisms may be involved in the formation of these structures. The microscopic structure and optoelectronic properties of surfaces covered with nanosecond or femtosecond laser cones could therefore differ as well. We compare the optical... Read more about Comparing properties of femtosecond and nanosecond laser-structured silicon
Early stages of femtosecond laser-induced formation of silicon microspikes, at Materials Research Society Fall Meeting (Boston, MA), Monday, December 2, 2002:
talk_450.pdf
Arrays of sharp conical spikes form on crystalline silicon surfaces when irradiated with a train of femtosecond laser pulses in a background of sulfur hexafluoride (SF6); blunter, more irregular microstructures form in vacuum. The tips of the spikes are at the height of the original surface of the wafer, suggesting that the formation process predominantly involves removing material. The spikes are arranged in a quasi-ordered fashion with a characteristic nearest-neighbor separation of a few micrometers; the exact value of this characteristic separation depends on the laser fluence and number... Read more about Early stages of femtosecond laser-induced formation of silicon microspikes
Femtosecond Techniques for Materials Scientists, at Materials Research Society Annual Meeting (Boston, MA), Sunday, December 1, 2002:
talk_439.pdf
The tutorial starts at a basic level, so everyone starts out on solid ground, but then quickly advances to state-of-the-art femtosecond techniques. The first part of the tutorial deals with the interaction of light with matter and, after refreshing some basic concepts of electromagnetism, moves on to nonlinear optical processes that are relevant for the propagation of femtosecond laser pulses. The second part deals with measurement techniques. Part of the tutorial will be taught in an interactive format. That is to say, the participants will work through a number of problems in small groups... Read more about Femtosecond Techniques for Materials Scientists
Stopping Time, at Sigma Xi Lecture, Air Force Research Laboratory, Hanscom Air Force Base (Lincoln, MA), Wednesday, November 20, 2002:
talk_438.pdf
Memorization or understanding: Are we teaching the right thing?, at Physics Colloquium, University of Strathclyde (Glasgow, United Kingdom), Monday, November 11, 2002:
talk_446.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 Memorization or understanding: Are we teaching the right thing?
Femtosecond laser-assisted microstructuring of silicon for novel detector, sensing, and display technologies, at IEEE/LEOS 2002 Conference on Electro-Optic Sensors and Systems (Glasgow, Scotland), Monday, November 11, 2002:
talk_424.pdf
Arrays of sharp, conical microstructures are obtained by texturing the surface of a silicon wafer using femtosecond laser-assisted chemical etching. The one step, maskless texturing process drastically changes the optical, material and electronic properties of the original silicon wafer. These properties make the textured silicon viable for use in a wide range of commercial devices. First, near-unity absorption of light, from visible to infrared wavelengths, offer opportunities for use in optically active devices such as solar cells and detectors. Significant enhancement of below-band-gap... Read more about Femtosecond laser-assisted microstructuring of silicon for novel detector, sensing, and display technologies

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