Effect of Fused Silica Deposition Method on a Laser Performance of Multilayered Dielectric Gratings

Chirped pulse amplification (CPA), a method for producing ultrashort, high peak intensity laser pulses, is used in multiple applications including medical treatments, material processing, ultra-fast spectroscopy, and high-energy-density physics. An arrangement of four optical gratings stretches our laser pulses temporally and spectrally, amplifies them, and compresses them again, producing shorter pulses with a much higher peak intensity. One current limitation to CPA is the optical gratings damage at lower laser fluences than the intrinsic damage threshold of pure unprocessed silica coating that is used to make the grating lines, suggesting that the grating manufacturing process induces defects and contaminants that absorb laser light and cause premature damage. Of the possible sources of damage, the effect of the silica coating method on the laser damage performance of the CPA gratings is not well evaluated. To better understand how different types of silica coatings change during the grating manufacturing, we developed a protocol to evaluate physical, chemical, and laser damage properties of the silica coatings before and after the grating manufacturing cycle. After performing a reactive ion etch process, etch selectivity, surface chemical composition, surface roughness, and damage test performance were evaluated for a silica coating deposited via electron beam evaporation. Future experiments will compare these metrics with other SiO2 coating methods to determine the optimal coating process for maximizing laser damage resistance.

This material is based upon work supported by the Department
of Energy [National Nuclear Security Administration] University of Rochester
“National Inertial Confinement Fusion Program” under Award Number(s)
DE-NA0004144.