Tutorial on Silicon Photonics Integrated Platform Fiber Edge Coupling

TL;DR

This tutorial reviews low-loss coupling strategies for silicon nitride photonic integrated circuits, highlighting optimized designs and manufacturing techniques that significantly reduce coupling losses for fiber-to-chip connections.

Contribution

It provides a comprehensive overview and practical guidance on coupling technologies, optimized designs, and fabrication methods for efficient fiber-to-chip coupling in silicon nitride PICs.

Findings

Achieved -0.15 dB coupling loss with optimized inverted tapers and UHNA-7 fiber.

Measured -1.50 dB coupling loss with standard single-mode fiber.

Demonstrated effective coupling for both TE and TM modes.

Abstract

Photonic integrated circuits (PICs) play a crucial role in almost every aspect of modern life, such as data storage, telecommunications, medical diagnostics, green energy, autonomous driving, agriculture, and high-performance computing. To fully harness their benefits, an efficient coupling mechanism is required to successfully launch light into waveguides from fibers. This study introduces low-loss coupling strategies and their implementation for a silicon nitride integrated platform. Here we present an overview of coupling technologies, optimized designs, and a tutorial on manufacturing techniques for inverted tapers, which enable effective coupling for both transverse-magnetic and transverse-electric modes. The optimized coupling losses for the UHNA-7 fiber and the inverted taper Si3N4 coupler reached -0.15 dB at 1550 nm per connection for single-mode waveguides with 220x1200 nm cross section. The measured coupling losses in the inverted taper coupler with a standard single-mode fiber were -1.50 dB at 1550 nm per connection for the same platform.