Laser Thermal Compaction of Nanoporous Glasses

The processes of thermal compaction of nanoporous glass surfaces using carbon dioxide laser radiation have been investigated. Successful formation of a thermally compacted layer with a thickness of (20 ± 1) μm was demonstrated under the following thermal compaction regime: average radiation power 10.5 W, defocusing ∆f = 16 mm of an F-theta lens with a focal length of 157 mm, scan speed 40 mm/sec, and track spacing 100 μm. It was shown that birefringent structures can be recorded through the thermally compacted layer using femtosecond pulses, with the magnitude of their phase shift serving as an indirect indicator of glass porosity.