Presentations

    Micromachining of bulk glass with tightly-focused femtosecond laser pulses, at XI International Symposium Ultrafast Phenomena in Spectroscopy, Academia Sinica (Taipei, Taiwan), Tuesday, October 26, 1999:
    By focusing femtosecond laser pulses with high numerical-aperture microscope objectives, we micromachine optical glass using energies that are in the range of modern laser oscillators. When a femtosecond laser pulse is tightly focused inside a transparent material, energy deposition occurs only at the focus, where the laser intensity is high enough to cause absorption through nonlinear processes. When enough energy is deposited, the material is damaged and a localized change in the index of refraction is produced. By scanning the focus through the sample, very precise, three-dimensional... Read more about Micromachining of bulk glass with tightly-focused femtosecond laser pulses
    Teaching and Research: Inseparable responsibilities of the modern physicist, at Advisory Committee Meeting, National Science Foundation, Directorate for Mathematical and Physical Sciences (Arlington, VA), Thursday, April 13, 2000:
    Mention the word ""physics"" to the average high-school student and you are not likely to see many happy faces. Public opinion of science in general--and physics in particular--is not high. More importantly, misunderstandings about the goals and procedures of physics are rampant. In part, these problems arise because physics education has focused nearly exclusively on generating a steady supply of future physicists. The need to educate non-majors, let alone the public at large, has generally not been perceived as an important mission of physics departments. Now that the need for physics is no... Read more about Teaching and Research: Inseparable responsibilities of the modern physicist
    Laser-Solid Interactions for Materials Processing, at 2000 Materials Research Science Meeting (San Francisco, CA), Wednesday, April 26, 2000:
    By focusing femtosecond laser pulses with high numerical-aperture microscope objectives, we micromachine optical glass using energies that are in the range of modern laser oscillators. When a femtosecond laser pulse is tightly focused inside a transparent material, energy deposition occurs only at the focus, where the laser intensity is high enough to cause absorption through nonlinear processes. When enough energy is deposited, a localized change in the index of refraction is produced, i.e. the material is damaged. By scanning the focus through the sample, very precise, three-dimensional... Read more about Laser-Solid Interactions for Materials Processing
    Education: Transfering information or engaging the mind?, at Education Seminar, Department of Mathematics, University of Washington (Seattle, WA), Wednesday, May 10, 2000:
    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 Education: Transfering information or engaging the mind?
    Stopping Time, at 2000-2001 Lowell First Friday Lectures, Museum of Science (Boston, MA), Friday, October 6, 2000:
    Time is of philosophical interest as well as the subject of mathematical and scientific research. Even though it is a concept familiar to most, the passage of time remains one of the greatest enigmas of the universe. The philosopher Augustine once said: "What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know." The concept time indeed cannot be explained in simple terms. Emotions, life, and death - all are related to our interpretation of the irreversible flow of time. After a short introduction to the concept of time, Dr. Mazur... Read more about Stopping Time
    Microexplosions: controlling matter with light, at Frontiers in Chemistry and Materials Science Symposium, Lawrence Livermore National Laboratory (Livermore, CA), Thursday, October 19, 2000:
    Light travels undisturbed through a window pane because glass is transparent -- light and glass don't interact. With a powerful femtosecond laser pulse, however, nonlinear processes give rise to light-matter interactions that open the door to new studies in materials science, chemistry, condensed matter physics, and life sciences. Even at very modest energies, the intensity of a tightly-focused, femtosecond laser pulse can be high enough to cause nonlinear absorption of laser energy by a transparent material. The absorption is confined at the focus producing extreme conditions in the... Read more about Microexplosions: controlling matter with light
    Femtosecond micromachining of transparent materials, at OSA 2000 Annual Meeting (Providence, RI), Tuesday, October 24, 2000:
    By tightly-focusing femtosecond laser pulses, we achieve the intensity required for permanent structural change in transparent materials with only nanojoules of energy. We discuss the mechanisms and morphology of bulk structural changes produced by femtosecond laser pulses, and describe recent work on the direct writing of photonics devices using only a laser oscillator.
    Ultrafast Phase Transitions in Semiconductors, at 2000 MRS Fall Meeting (Boston, MA), Tuesday, November 28, 2000:
    We present measurements of the dielectric function of various semiconducting materials (c-GaAs, a-GaAs and GeSb thin-films) over a broad energy range (1.5 - 3.5 eV) with a time resolution of 70 fs after the excitation with an ultrashort laser pulse. The time evolution of the dielectric function provides a wealth of information that allows identification and tracking of the electronic and structural dynamics triggered by the pump pulse. At elevated fluence levels all materials undergo a semiconductor to metal transitions.
    Fabrication of Micrometer-Sized Conical Field Emitters Using Femtosecond Laser-Assisted Etching of Silicon, at MRS Spring Meeting (San Francisco, CA), Friday, April 20, 2001:
    We produce quasi-ordered arrays of sharp, conical microstructures by structuring the surface of a silicon wafer using femtosecond laser-assisted etching. Analysis of the arrays shows high, stable field emission without any further processing. The sharp, micrometer-sized conical structures result from irradiation of a silicon surface with hundreds of femtosecond-laser pulses in an atmosphere of SF6. These conical microstructures have sharp tips with a radius of curvature of about 250 nm and a subtended angle of less than 20°. They are 10–14 µm tall, have tip-to-tip separations of 6–10 µm, and... Read more about Fabrication of Micrometer-Sized Conical Field Emitters Using Femtosecond Laser-Assisted Etching of Silicon
    Micromachining and laser processing with ultrashort laser pulses, at Second International Symposium on Laser Precision Microfabrication (LPM2001) (Singapore), Wednesday, May 16, 2001:
    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 Micromachining and laser processing with ultrashort laser pulses
    Black silicon: hot properties and many open questions, at Atomic and molecular physics at surfaces, ITAMP (Cambridge, MA), Thursday, June 14, 2001:
    A serendipitous discovery in our lab produced a novel form of microstructured silicon ("black silicon") that has many surprising properties: near unity absorption, even below the bandgap; production of photoelectrons in the visible and infrared; visible luminescence; and a strong field emission current. We are beginning to shed light on what might cause some of the material's remarkable properties. Much additional experimental and theoretical work is required to understand the surface physics and chemistry that leads to the formation of black silicon.
    Laser induced microexplosions and applications in laser micromachining, at Annual Meeting of the Stanford Photonics Research Center, Standord University (Palo Alto, CA), Saturday, September 15, 2001:
    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 Laser induced microexplosions and applications in laser micromachining

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