Laser-based micro-machining of low-loss fused silica waveguides for integrated photonics

The miniaturization of photonic integrated systems requires new monolithically integrated components and micro-fabrication technologies able to guarantee high resolution and to enable a wide and cost-effective deployment. Laser-based glass micro-machining allows writing 3D waveguides within the bulk of the glass, which can be used as photonic wire connections within photonic integrated circuits or their package and assembly components to guarantee effective fiber-chip or chip-to-chip connectivity. In this article, we present low-loss fused silica waveguides and their performance in terms of mode field diameter (MFD) as well as insertion, propagation and bending losses at different wavelengths in the telecom NIR windows. For a comprehensive analysis, a comparison with state-of-the-art waveguides fabricated either in fused silica or in borofloat 33 is provided. Specific examples of tapers, mode field converters, or fan-in/-out devices are presented to fully demonstrate the potential of our laser-based micro-machined low-loss silica waveguides for packaging and assembly applications in integrated photonics.