3D Laser Structured Mirror-Waveguide Circuits: a New Optical PCB Platform for Silicon Photonics

The demands for faster networks and growing requirements in data centers have spurred the development of photonic integrated circuits [1] , particularly in designing a universal platform for optical/electrical interconnects. Some headway towards an optical PCB platform has been made, for instance, chip-to-chip polymer waveguide interconnects [2] , ion-exchange waveguide flip-chip packaging [3] , and laser-written 3D circuits in glass [4] . However, the design of an all-optical platform for chip-to-chip or chip-to-network (i.e. chip-to-fiber) communications still faces challenges, namely densification of I/O channels and bending radius constraints for optical waveguide routing. The latter can be addressed by using total internal reflection (TIR) surfaces to bend light at sharp angles, such as for compact fiber coupling to Silicon Photonics (SiP) gratings with a polished glass wedge or angled SMF array [5] . In this regard, we propose a platform which utilizes femtosecond laser assisted chemical etching to embed TIR micro-mirrors and facilitate sharp bending of optical waveguide circuits inside of fused silica glass. Full 3D optical routing is proposed with multi-level waveguides and high channel-density.