"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
Abstract:
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
