Thursday, July 25, 2013

SEMINAR: "Effects of laser-field enhancement in laser-induced damage" by Dr. Vitaly Gruzdev, Ph.D./ 8.08.13/ 11:00-12:00pm/ CREOL 102

"Effects of laser-field enhancement in laser-induced damage” Dr. Vitaly Gruzdev
Thursday, August 8th, 2013 from 11:00 AM to 12:00PM
CREOL room 102

Dr. Vitaly Gruzdev, Ph.D.
Department of Mechanical and Aerospace Engineering, University of Missouri
Columbia, MO 65211

In most cases, microscopic mechanisms of high-power laser-material interactions (including laser-induced damage (LID)) are driven by local value of electric field of laser radiation. The electric field cannot be directly measured during the laser-material interaction event, and laser fluence is the most popular measure to characterize the interactions. Under the standard approaches, the fluence is evaluated from measured energy of a laser pulse divided by measured (or simulated) laser-spot area. The point of this presentation is that the relation between the so measured fluence and amplitude of electric field of laser radiation is not trivial. To illustrate it, propagation of laser radiation through materials with non-homogeneous structure (e.g., multi-layer coatings) is considered. Multiple reflections during that propagation result in local enhancement of laser electric field due to interference effects. The enhanced electric field must result in intensifying the laser-material interactions and reduction of LID threshold. As examples of that interconnection between electric-field enhancement and LID threshold, Fresnel reflection at rear surface of optical windows, interference in multilayer coatings, and local field enhancement at surface scratches are referred to. Electric-field distribution is analyzed for those effects based on rigorous Maxwell’s equations under the approximation of linear propagation of monochromatic radiation. From distribution of laser electric field in space, energy flux and energy density are evaluated according to Poynting’s theorem. Then, radiation-energy transfer through the materials is discussed to uncover the true relations between the field enhancements and amount of laser fluence calculated from measured pulse energy divided by laser-spot area. Of special attention is the correct evaluation of laser fluence and local electric field at front and rear surfaces of thin transparent slabs in view of the well-established low damage threshold of the rear surfaces compared to the front surface.

Short Bio:
Vitaly Gruzdev graduated from St. Petersburg Institute of Fine Mechanics and Optics with honors in 1994. In 2000 he received Ph. D. from S. I. Vavilov State Optical Institute (St. Petersburg, Russia). In 2001-2003 he was a visiting researcher at the group of Prof. Dr. D. von der Linde (University of Essen, Germany). Since 2005 he is with the Department of Mechanical and Aerospace Engineering, University of Missouri. He has been working in the field of high-power laser-material interactions and laser-induced damage for more than 20 years. His current research interests include theoretical studies of laser-induced photo-ionization of solids and related laser effects. He has more than 100 publications on the topic. Since 2009 he is a co-chair of SPIE Laser Damage Symposium held annually in Boulder, CO, USA. In 2012 he co-edited a special section of Optical Engineering devoted to Laser Damage.

For more information:
E-mail: gruzdevv @ missouri . edu
Phone: (573) 882-7292

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