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2009

Applications of femtosecond lasers in materials processing, at Conference on Lasers and Electro-Optics Europe (Munich, Germany), Wednesday, June 17, 2009:
talk_1438.pdf
Chemical bonding, phase transitions, and surface processes occur on timescales comparable to the natural oscillation periods of atoms and molecules, in the range of femtoseconds (1 fs =10�15 s) to picoseconds (1 ps = 10�12 s). Advances in the generation of ultrashort laser pulses in the past two decades have made it possible to directly observe these fundamental processes. These advances have taken us from the picosecond timescale a generation ago, to the femtosecond timescale in the past decade, and recently into the attosecond (1 as = 10�18 s) regime. Materials science,... Read more about Applications of femtosecond lasers in materials processing
Memorization or understanding: are we teaching the right thing?, at 1st Danish Physical Society Nordic Meeting, Technical University of Denmark (Copenhagen, Denmark), Tuesday, June 16, 2009:
talk_1461.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. I will show how shifting the focus in lectures from delivering information to synthesizing... Read more about Memorization or understanding: are we teaching the right thing?
The scientific approach to teaching: Research as a basis for course design, at 1st Joint Nordic Physical Society Meeting: Education Societies Premeeting, Technical University of Denmark (Copenhagen, Denmark), Tuesday, June 16, 2009:
talk_1462.pdf
Discussions of teaching -- even some publications -- abound with anecdotal evidence. Our intuition often supplants a systematic, scientific approach to finding out what works and what doesn't work. Yet, research is increasingly demonstrating that our gut feelings about teaching are often wrong. In this talk I will discuss some research my group has done on gender issues in science courses and on the effectiveness of classroom demonstrations.
Black silicon, at Technical University of Denmark (Copenhagen, Denmark), Tuesday, June 16, 2009:
talk_1485.pdf
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.
Confessions of a converted lecturer, at Dedication of the Centre for Science Education, Aarhus University (Århus, Denmark), Monday, June 15, 2009:
talk_1473.pdf
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
Nonlinear optics at the nanoscale, at Research Seminar, University of Twente (Enschede, The Netherlands), Friday, June 12, 2009:
talk_1483.pdf
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
Black silicon, at Research Seminar, University of Twente (Enschede, The Netherlands), Friday, June 12, 2009:
talk_1484.pdf
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.
Femtosecond laser micromachining for applications in microphotonics, at E-MRS Meeting (Strassbourg, France), Thursday, June 11, 2009:
talk_1409.pdf
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.
Black silicon, at Conversation with Researchers and Students, Benemérita Universidad Autónoma de Puebla (Puebla, Puebla, Mexico), Friday, May 29, 2009:
talk_1479.pdf
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.
Nonlinear optics at the nanoscale, at Optoelectronics Seminar, Benemérita Universidad Autónoma de Puebla (Puebla, Puebla, Mexico), Thursday, May 28, 2009:
talk_1478.pdf
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

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