Contamination is a primary concern in the optics and electronics industry since it can lead to both reduced
performance and premature failures. This work is concerned with evaluating the performance of laser based cleaning
methods for removal of contaminants (dielectrics, metals) from the surface of optics. In general, the art of cleaning
contaminants from surfaces is a balance between the energy used to remove the contaminant while minimizing the
amount that is applied to the substrate.
In this work we present our work with a dry, non-contact method of cleaning that is ideal for, but not limited to,
delicate surfaces where traditional contact cleaning methods are not possible. The photo-absorption technique being
explored utilizes the absorbed laser light in the surface to thermo-mechanically remove the particle from the substrate.
In this work, the process of photo-absorption method will be discussed and the challenges associated with this cleaning
method will be presented.
The current research focused upon ascertaining the extent of induced laser damage that occurs due to the
outgassing species from adhesives that will contaminate the optics. The adhesives that are being studied
are actual flight materials that are being used in mounting optics in existing 1064nm LIDAR laser
systems. Three different adhesives were tested in our vacuum system. Each sample was loaded onto an
effusive source and a PID controller controls the set point temperature of the adhesive. The optics that
were tested were anti-reflective coated BK7 windows. An oil free vacuum pump system was used to
pump the system down to approximately 10-5 Torr. The vacuum pressure of the system was measured by
use of a thermocouple gauge and a Bayard Alpert ion gauge. The test windows were irradiated with a 20
Hz Nd:YAG laser at 1064 nm with a nominal fluence of 1 J-cm-2 for at least 1 million shots. All sample
windows are analyzed by use of bright field and dark field light microscope. Under the test conditions
that were performed, varying extent of damage with different morphologies were observed; making it
difficult to specify a single damage mechanism that would adequately explain the vast differences