NEO-PGA: Nonvolatile electro-optically programmable gate array

TL;DR

This paper introduces a scalable, nonvolatile photonic FPGA using phase-change materials integrated on silicon, enabling low-power, multi-bit reconfigurable optical circuits with high precision and broadband capabilities.

Contribution

It demonstrates the first precise, multi-bit, low-loss PCM tuning method and implements reconfigurable silicon photonic gates on a large-scale platform, advancing programmable photonics.

Findings

Achieved multi-bit, low-loss tuning of Sb2Se3 PCM.

Implemented reconfigurable optical switches and resonators.

Showcased scalable, nonvolatile photonic FPGA architecture.

Abstract

Programmable photonic integrated circuits (PICs) offer a unique opportunity to create a flexible platform, akin to electronic field programmable gate array (FPGA). These photonic PGAs can implement versatile functionalities for applications ranging from optical interconnects to microwave photonics. However, state-of-the-art programmable photonics relies predominantly on volatile thermo-optic tuning, which suffers from high static power consumption, large footprints, and thermal crosstalk. All these dramatically limit the gate density and pose a fundamental limit to the scalability. Chalcogenide-based phase-change materials (PCMs) offer a superior alternative due to their nonvolatility and substantial optical contrast, though challenges such as optical loss, and bit precision severely limited their application in large-scale PICs. Here, we demonstrate precise, multi-bit, low-loss tuning of the emerging PCM Sb2Se3 using a closed-loop, "program-and-verify" method. Electrically reconfigurable PCM-integrated silicon photonic gates are implemented on a 300mm silicon photonic platform, using circulating and forward Mach-Zehnder interferometer (MZI) meshes. In the circulating mesh, we realize broadband optical switching fabrics and high-Q coupled resonators with unprecedented local control of coupling rates, which further enable exploration of coupled-cavity systems. The forward mesh supports self-configurable MZIs that sort two orthogonal beams to different ports. These results showcase a new type of scalable photonic PGA enabled by PCMs, offering a pathway toward general-purpose, on-chip programmable photonic systems.