Fs-laser-based structuring of fused silica towards fully glass-integrated waveguides and sensors

Selective laser etching (SLE) allows to create versatile and highly precise 3-dimensional structures in glass by subtractive manufacturing. The process itself is based on two main steps. First, the designed structure is transferred into the glass substrate by a fs-pulsed laser. Subsequently, the sample is placed in a lye where only the pre-structured part of the material is removed. The influence of different writing parameters such as laser power, repetition rate, laser polarization, stage motion speed, hatching and slicing have been studied before towards an optimized surface roughness. By adding an additional annealing step before starting the etching process we were able to achieve surface roughness values of ⁓25nm which is sufficient for optical application. In our current work, we use the SLE process to produce channels for single-mode waveguides and waveguide splitters, which are subsequently filled with a core material and equipped with a fiber connection to simplify light coupling. Pushing this process to the limits, we designed, fabricated and characterized in-glass embedded ring resonators suitable for sensing applications.