Laser Induced Damage
Space is a very challenging environment for optics and optical coatings that need to operate with high energy regime laser. High energy, high number of shots, outgassing material in the FOV and no possibility of replacement are some of the problems that we need to face while building high energy laser for space. For this reason an early screen of the optics in a representative ambient could be crucial for the success of the mission. The Laser-Induced Damage (LID) facility in TEC-MME section is the worldwide only ISO21254-2 accredited laboratory.
The main goal is to test and qualified optics used in high power laser in representative condition for space application.
The source used is a ND:YAG laser with a repetition rate of 100Hz and wavelengths going from 1064nm to 355nm. An automated software allows to test optics in S-on-1 or raster scan mode. The samples are generally placed in a vacuum chamber and can be tested in different environmental condition (in vacuum or pressurized with oxygen, synthetic air, etc) to simulate the nominal condition that will be used for the flight modules. The damage recognition is performed on-line and eventually corrected after the microscope inspection of the sample. The evaluation of the data deliver a probabilistic damage curve that give an information on the nominal level of fluence that a certain optics could stand for a determinate number of shots. Raster scan is in general performed at the nominal fluence over a larger area of the sample to allow the detection of low density precursors. The scan of the flight optics is now a common practice for ESA mission.