Index Modulation Embedded in Type I Waveguide Written by Femtosecond Laser in Fused Silica

Slit-shaped laser beams focused in bulk optical materials can realize embedded waveguides with circular cross sections consisting of positive index change type I traces. In these kinds of waveguide traces, a peculiar periodical refractive index modulation was observed in type I waveguides with two different femtosecond lasers. The direction of refractive index modulation can be controlled with the slit configuration, and its period can be controlled by mechanical perturbation of the stages and the scanning speed. We argue that platform perturbation and dynamical thermal transport processes during the scan are generating factors in the appearance of this modulation. The embedded microstructures in waveguides can provide spectrum modulation, which may have potential applications in optical sensing, filtering, and phase control.

Automated summary

It was found that using different femtosecond lasers to focus in bulk optical materials can form embedded waveguides with circular cross sections consisting of positive index change type I traces, where a periodic refractive index modulation was observed. The direction and period of the refractive index modulation can be controlled by factors such as the slit configuration, mechanical perturbation, and scanning speed. The embedded microstructures in waveguides can be used for spectrum modulation, potentially valuable for applications in optical sensing, filtering, and phase control.