# Advances in waveguide to waveguide couplers for 3D integrated photonic packaging

## TL;DR

This paper reviews and compares various waveguide coupling technologies for 3D photonic integration and their applications in energy-efficient optical systems.

## Contribution

The paper provides a comprehensive overview and comparison of waveguide-to-waveguide coupling devices and their 3D integration technologies for photonic packaging.

## Key findings

- Various waveguide couplers like inter-chip edge and grating couplers are compared for photonic integration.
- Guided mode and free form photonic vias are discussed for efficient light transmission through different substrates.
- Applications like co-packaged optics and LiDAR systems show potential improvements in energy efficiency and performance.

## Abstract

In this paper, we provide an overview and comparison of devices used for optical waveguide-to-waveguide coupling including inter-chip edge couplers, grating couplers, free form couplers, evanescent couplers, cantilever couplers, and optical wirebonds. In addition, technology for efficient transmission of light through chips is discussed including guided mode and free form photonic vias for substrates including silicon, glass, and organics. The results are discussed in the context of potential applications including co-packaged optics switch packages, replaceable biochemical sensors, optically connected memory, optical computing, integrated quantum photonics, and integrated LiDAR systems to show possible improvements in energy efficiency, performance, and cost.

The automated packaging and assembly of a photonic chiplet to an optical interposer and printed circuit board is shown, where optical inter-chip couplers, wirebonds, and vias provide 3D waveguide connectivity.