Investigation of structural mechanisms of laser-written waveguide formation through third-harmonic microscopy.

The mechanisms of laser-induced modification of transparent materials are complex combinations of different processes that depend on the material itself and a range of processing parameters. As such, the mechanisms are still subject to ongoing study. We use a custom-built adaptive third-harmonic generation (THG) microscope to study those mechanisms. New femtosecond-laser-written phenomena are revealed through this method of imaging. This Letter, together with previous reports by Miyamoto Opt. Express 24, 25718 (2016) and Fernandez J. Phys. D 48, 155101 (2015) suggest that the distribution of the generated plasma during writing is responsible for the newly revealed phenomena. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.