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Mechanisms to Explain Damage Growth in Optical Materials.

DE200515013200

Publication Date	2000
Personal Author	Demos, S. G.; Kozlowski, M. R.; Staggs, M.
Page Count	12
Abstract	Damage growth in optical materials used in large aperture laser systems is an issue of great importance when determining component lifetime and therefore cost of operation. Understanding the mechanisms and photophysical processes associated with damage growth are important in order to devise mitigation techniques. In this work we examined plasma-modified material and cracks for their correlation to damage growth on fused silica DKDP samples. We employ an in-situ damage testing optical microscope that allows the acquisition of light scattering and fluorescence images of the area of interest prior to, and following exposure to a high fluence, 355-nm 3-ns laser pulse. In addition, high-resolution images of the damage event are recorded using the associated plasma emission. Experimental results indicate that both aforementioned features can initiate plasma formation at fluences as low as 2 J/cm2. The intensity of the recorded plasma emission remains low for fluences up to approximately 5 J/cm2 but rapidly increases thereafter. Based on the experimental results, we propose as possible mechanisms leading to damage growth the initiation of avalanche ionization by defects at the damage modified material and presence of field intensification due to cracks.
Keywords	Damage growth Optical materials Laser damage Photophysical processes Plasma-modified materials Cracks Fused silica Optical microscopes Silicon dioxide Optical breakdown DKDP
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200602

Mechanisms to Explain Damage Growth in Optical Materials.

Mechanisms to Explain Damage Growth in Optical Materials.
DE200515013200

Publication Date	2000
Personal Author	Demos, S. G.; Kozlowski, M. R.; Staggs, M.
Page Count	12
Abstract	Damage growth in optical materials used in large aperture laser systems is an issue of great importance when determining component lifetime and therefore cost of operation. Understanding the mechanisms and photophysical processes associated with damage growth are important in order to devise mitigation techniques. In this work we examined plasma-modified material and cracks for their correlation to damage growth on fused silica DKDP samples. We employ an in-situ damage testing optical microscope that allows the acquisition of light scattering and fluorescence images of the area of interest prior to, and following exposure to a high fluence, 355-nm 3-ns laser pulse. In addition, high-resolution images of the damage event are recorded using the associated plasma emission. Experimental results indicate that both aforementioned features can initiate plasma formation at fluences as low as 2 J/cm2. The intensity of the recorded plasma emission remains low for fluences up to approximately 5 J/cm2 but rapidly increases thereafter. Based on the experimental results, we propose as possible mechanisms leading to damage growth the initiation of avalanche ionization by defects at the damage modified material and presence of field intensification due to cracks.
Keywords	Damage growth Optical materials Laser damage Photophysical processes Plasma-modified materials Cracks Fused silica Optical microscopes Silicon dioxide Optical breakdown DKDP
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200602