SYMPOSIA PAPER Published: 01 January 1988

The Discovery of Laser-Induced Intrinsic Optical Damage in Wide-Gap Materials at Visible Wavelength


After two decades of research, the question “What is the nature of intrinsic breakdown of wide-gap optical materials exposed to short laser pulses at visible wavelength?” has recently been answered unambiguously for two cases: 532 nm, picosecond pulses tightly focused in NaCl and KBr. This remarkable achievement warrants some reflection on its impact on the field of high laser power optical materials.

Clearly, the problem of extrinsic damage to coatings and surfaces remains unsolved and formidable, and the quest for higher damage thresholds will continue without any realistic hope to achieve intrinsic behavior in the foreseeable future. However, such pessimistic realism is no longer justified for bulk breakdown, because the possibility of fabricating intrinsic high-power optical materials—not just alkali halides, but also technologically important alkaline earth halides and metal oxides—must now be taken seriously.

In light of this new development we will re-examine the results of some classic damage experiments and the conclusions on the laser damage mechanisms that were based on erroneous assumptions of intrinsic material behavior. Extrinsic damage, presumed to be intrinsic for the purpose of data interpretation, will always appear to be avalanche formation via electron impact ionization if only damage thresholds are measured.

With this in mind, we will look again at self-focusing and defocusing effects, the traditional exclusive reliance on subjectively defined damage criteria and, thus, uncertain thresholds, and the role of primary laser-generated photo-chemical defects in the historical “workhorse” materials, the alkali halides.

Author Information

Braunlich, P
Jones, SC
Shen, XA
Casper, RT
Kelly, P
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Developed by Committee: E13
Pages: 476–484
DOI: 10.1520/STP24459S
ISBN-EB: 978-0-8031-5033-1
ISBN-13: 978-0-8031-4481-1