Photonic devices based on phase-change materials for neuromorphic computing

Abstract

This paper reviews recent advances in the field of photonic devices integrating phase-change materials (PCMs). In particular, certain PCMs showcase interesting properties such as non-volatile behaviour and ultra-low optical losses that can be leveraged in computing architectures. For example, they can operate as complex-valued weights enabling ultra-low power consumption matrix-vector multiplications. Here, we first review the optical properties of multiple PCM compounds as interesting candidates for photonic computing. Then, we discuss about GeSe-based electrically activated photonic devices that exploit such properties in novel device concepts. Specifically, we present a hybrid-mode interferometer and an asymmetric heater geometry along the propagation direction for electrical PCM actuation. These approaches lead to a higher number of encoded states as well as ultra-low optical insertion losses compared to previous implementations, while retaining a compact footprint and practical driving conditions. Finally, we present experimental results for optically actuated Ge 2 Sb 2 Te 5 (GST225) based waveguides in terms of encoding capabilities and reliability for all-optical reconfigurability and processing.