The influence of femtosecond laser wavelength on waveguide fabrication inside fused silica

We have investigated the effect of the laser wavelength on the fabrication of optical waveguides and tracks of modified material via direct laser writing inside fused silica. The size of the laserinscribed tracks, the material modification thresholds, the structural changes, and the waveguide writing energy range show a strong dependence on laser wavelengths ranging from ultraviolet to near-infrared. We used numerical simulations that consider the laser-excited electron plasma dynamics (via multiple rate equations) along with Gaussian beams theory to calculate the size of the laser-affected volume that has been further compared with the experimental results. This study yields insight into how to predict and design the spatial features of laser-inscribed lines and also aids of understanding the underlying physical mechanisms linked to laser-glass interaction when using different laser wavelengths.