Effect of Substrate Temperature on Morphological, Structural, and Optical Properties of Doped Layer on SiO 2 -on-Silicon and Si 3 N 4 -on-Silicon Substrate.

A high concentration of Er 3+ without clustering issues is essential in an Er-doped waveguide amplifier as it is needed to produce a high gain and low noise signal. Ultrafast laser plasma doping is a technique that facilitates the blending of femtosecond laser-produced plasma from an Er-doped TeO 2 glass with a substrate to form a high Er 3+ concentration layer. The influence of substrate temperature on the morphological, structural, and optical properties was studied and reported in this paper. Analysis of the doped substrates using scanning electron microscopy (SEM) confirmed that temperatures up to approximately 400 °C are insufficient for the incoming plasma plume to modify the strong covalent bonds of silica (SiO 2 ), and the doping process could not take place. The higher temperature used caused the materials from Er-doped tellurite glass to diffuse deeper (except Te with smaller concentration) into silica, which created a thicker film. SEM images showed that Er-doped tellurite glass was successfully diffused in the Si 3 N 4 . However, the doping was not as homogeneous as in silica.