The lifetime of optical components submitted to high laser fluences is degraded under organic contaminant environment.
The molecular background of the Ligne d'Integration Laser (LIL), prototype of the future Laser Megajoule, might reduce
the laser damage threshold of exposed fused silica surfaces. This paper reports the interaction effects between pure
model contaminant deposits and a pulsed 1064 nm laser radiation on the coming out of mirror damage. The experimental
setup allowed us to condense nanolayers of model contaminants on optics, the deposit impacts were then investigated by
Laser Induced Damage Threshold (LIDT) tests in Rasterscan mode. In order to highlight physical processes emphasizing
the emergence of optics damage, we characterized the irradiated deposit using interferometric microscopy analysis and
spectrophotometric analysis. The challenge was to determine physical and phenomenological processes occurring during
the irradiation of a pure contaminant deposit with a 1064 nm pulsed laser and to study the impact of this model
contaminant on the LIDT of dielectric SiO2/HfO2 mirrors.
Under vacuum conditions, the accumulation of low fluence laser pulses generally leads to an organic
contamination of the surface irradiated. This phenomenon reduces the optical component lifetime. Experimental
conditions such as laser characteristics, environment composition and structure of the coating strongly influence the
contamination mechanisms. Silica being the most employed material for optical coatings, this study aims at describing
the laser-induced contamination influence of silica coatings deposition techniques. E-Beam evaporated and Ion Beam
Sputtered silica thin films have been exposed to several billions 600 mJ/cm2 - 532 nm laser pulses under vacuum. This
paper presents the observations made on laser-induced contamination and discusses the physical mechanisms involved.
In the midst of the Mega Joule Laser project, a study of the impact of organic contamination on optical surfaces has been launched. Last year, we presented results on intentionally contaminated optics by outgassing products of a typical material of the LIL (Ligne d'Integration Laser, the prototype laser line of the future LMJ). A small quantity of organic contamination deposited on high reflective mirrors decreased their R/1 laser induced damage threshold. As the LIDT R/1 test procedure may "condition" the optical component, further raster scan tests have been implemented on new intentionally contaminated samples to assess the test procedure impact on the LIDT results for different contaminations. The aim of this work is double: -First, the impact of organic contamination deposited on optical surfaces by outgassing will be evaluated by laser induced damage threshold measurement, after a laser shot at nominal fluence ; -The second objective is to evaluate the real effects of "conditioning", notably towards organic contamination deposited on optics.
It is still assumed that optical components submitted to laser fluences orders of magnitude below their laser induced damage threshold (LIDT) will last for ever. However, depending upon environmental conditions, the accumulation of low fluence laser pulses leads to a progressive contamination and eventually to a damage of the optical components. In order to study the physics of the laser induceded contamination, a laser test bench has been developed. The experimental cell is dry-pumped and a mass spectrometer controls the environment around the optical component. An infrared camera diagnosis follows the sample surface temperature. This paper contains preliminary results obtained on anti-reflective coatings on fused silica tested at 532 nm with a pulse repetition rate of 10 kHz and a pulse width of 100 ns.