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

Abstract

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.

Ultrafast Laser Direct Writing in Glass: Thermal Accumulation Engineering and Applications

“…First, probing the temperature distribution and evolution during the interaction between the ultrafast laser and various glasses is fundamentally important but a tough task. [38][39][40] In addition, the complex distribution of RI and elements in various glass systems as well as the formation of self-organized structures implies that synergistic effect between the temperature gradient and other effects, such as pressure wave propagation and electric field redistribution, also plays an important role in the resultant phenomena and structures. However, the simulation and experimental studies on this synergistic effect are still rare.…”

“…[37,38] In this scenario, the ultrafast laser serves as an outstanding heat source that leads to rapid temperature change and plasma evolution. [37][38][39][40]…”

“…[26,60] RI distribution is also demonstrated to be influenced by the scan speed. [40] However, there is some difference. For example, Miyamoto et al reported that absorptivity does not depend on the scan speed.…”

“…Guan et al also implied that cross-sectional profiles of the fabricated waveguide inside the borosilicate glass (Corning EAGLE 2000) characterized by the third-harmonic generation (THG) microscope could be correlated with the plasma location, which depends on the pulse energy. [40] The complex plasma evolution processes and the different position of plasma result in distinct morphologies and RI distribution in the cross-sections. [43,44] Furthermore, adjusting the pulse energy may also tune the types of RI.…”