PLASMA ETCHING OF POLISHED GLASS AND CRYSTAL SUBSTRATES FOR PREPARING HIGH POWER LASER COMPONENTS

Our plasma etching technology targets the essential improvement of polished optical substrates (glasses, crystals) in order to increase their laser damage resistance and produce coated transparent optical components for high power laser applications.

The subsurface of polished substrates very often contains the so-called Beilby layer, contaminated with polishing residuals. This sub-layer effectively absorbs laser radiation (especially in UV spectral range) and becomes the weakest link of laser component coated with antireflection (AR) or any other type of transmitting dielectric coating (beam splitter, polarizer, etc.).

Developed low-energy plasma etching allows effective removal of this contaminated substrate subsurface layer. Extensive studies demonstrated an increase of fused silica (FS) substrate laser-induced damage threshold (LIDT) from initial 20 J/cm² up to 100-150 J/cm² (355 nm, 2 ns duration laser pulse, test 1-on-1) after plasma etching. Another advantage is that initial substrate surface roughness is maintained after the etching procedure. Plasma etched and coated with AR coating FS substrate demonstrated the increase of 3.4x of LIDT for 355nm laser pulse compared with unprocessed and simultaneously coated FS substrate. Developed technology was also further applied for the etching of various non-linear and laser crystals, such as spinel (MgAl₂O₄), BSO, YAG. A significant (at least 2-3 times) increase of their LIDT in the near-infrared spectral range was obtained. Several successful collaborations with industrial partners were executed.

 

Field tested / evaluated

Available for demonstration

Prototype available for demonstration

 

In-house know-how.

Industrial and (or) research institutions.

 

Dr. Giedrius Abromavičius

Phone +37060411153, e-mail: giedrius.abromavicius@ftmc.lt