Vertical optical ring resonators fully integrated with nanophotonic waveguides on silicon-on-insulator substrates

TL;DR

This paper presents the integration of vertical optical ring resonators with silicon nanophotonic waveguides on silicon-on-insulator substrates, enabling 3D photonic integration with out-of-plane coupling and potential for advanced optical routing and sensing.

Contribution

It introduces a novel method of rolling up strained TiO2 nanomembranes into microtubes on a chip, achieving vertical coupling with nanowaveguides for the first time.

Findings

Successful demonstration of vertical optical coupling at telecommunication wavelengths.

Fabrication of microtube cavity arrays with multi-waveguide integration.

Potential for multi-routing and high-throughput optofluidic sensing.

Abstract

We demonstrate full integration of vertical optical ring resonators with silicon nanophotonic waveguides on silicon-on-insulator substrates to accomplish a significant step towards 3D photonic integration. The on-chip integration is realized by rolling up 2D differentially strained TiO2 nanomembranes into 3D microtube cavities on a nanophotonic microchip. The integration configuration allows for out of plane optical coupling between the in-plane nanowaveguides and the vertical microtube cavities as a compact and mechanically stable optical unit, which could enable refined vertical light transfer in 3D stacks of multiple photonic layers. In this vertical transmission scheme, resonant filtering of optical signals at telecommunication wavelengths is demonstrated based on subwavelength thick walled microcavities. Moreover, an array of microtube cavities is prepared and each microtube cavity is integrated with multiple waveguides which opens up interesting perspectives towards parallel and multi-routing through a single cavity device as well as high-throughput optofluidic sensing schemes.