The thesis describes the establishment of a laser damage facility
in the ultra violet. The laser is a pulsed excimer laser (25 n sec)
capable of an output energy of 1 Joule at wavelengths of 193, 245,
308, 337 and 351 nm. The problems involved in making reliable
damage threshold measurements are addressed, such as energy calibration,
beam attenuation, damage detection and temporal and spatial beam
profiling. A computer controlled frame store and video system
enabling single shot spatial profiling and peak fluence measurements
to be performed is described. Such a system is essential if reliable
results are to be obtained from lasers whose spatial output cannot
be described by a Gaussian.
Using the damage facility, work has been performed on single crystal
Caf2 laser windows ascertaining the bulk and surface damage thresholds
as a function of crystal purity, surface finishing and polishing
procedures. The results of a T.E.M. study give an insight into the
fundamental damage mechanism of this material to be electron avalanche
breakdown. The role of transient primary defects in the bulk breakdown
of CaF2 has been investigated using dye laser probe techniques, and
indicate that the presence of U.V. generated self trapped excitons,
acting as sinks for the conduction band electrons, greatly enhances
the damage threshold.
Work on coatings using a LIMA (Laser-induced ion mass analyser)
is reported and the potential of this machine as a laser damage
diagnostic tool is explored.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.