During the annual NIST calibration testing done at the LHMEL facility in FY06 on its high energy Carbon-Dioxide lasers, the LHMEL II device suffered severe damage to the internal surface of its ZnSe output
coupler optics. The damage occurred during a high power, short duration run and it was believed to have
been the result of a significant amount of surface contaminants interacting with the LHMEL cavity beam.
Initial theories as to the source of the contamination led to the inspection of the vacuum grease that seals
the piping that supplies the source gases to the laser cavity. Other contamination sources were considered,
and analysis was conducted in an effort to identify the material found at the damage sites on the optic, but
the tests were mainly inconclusive. Some procedure changes were initiated to identify possible
contamination before high energy laser operation in an attempt to mitigate and possibly prevent the
continued occurrence of damage to the output coupler window. This paper is to illustrate the type and
extent of the damage encountered, highlight some of the theories as to the contamination source, and serve
as a notice as to the severity and consequences of damage that is possible even due to small amounts of
foreign material in a high energy laser environment.
KEYWORDS: Gas lasers, Cameras, High power lasers, Mirrors, Camera shutters, Carbon monoxide, Laser scattering, Heat flux, Spatial resolution, Laser applications
For the past 28 years, the Laser Hardened Materials Evaluation Laboratory (LHMEL) at the Wright-Patterson Air Force Base, OH, has worked with CO2 lasers capable of producing continuous energy up to 150 kW. These lasers are used in a number of advanced materials processing applications that require accurate spatial energy measurements of the laser. Conventional non-electronic methods are not satisfactory for determining the spatial energy profile. This paper describes continuing efforts in qualifying the new method in which a continuous, real-time electronic spatial energy profile can be obtained for very high power, (VHP) CO2 lasers.
Pulsed laser capabilities at the Laser Hardened Material Evaluation Laboratory are described relevant to optical coupling, impulse generation and laser propulsion. Capabilities of the Nd:Glass laser are presented as well as supporting test systems.
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