  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.
