An Ultra-low-loss Compact Phase-Change Material-based Hybrid-mode Interferometer for Photonic Memories

TL;DR

This paper introduces a hybrid-mode interferometer using phase-change materials in silicon photonics, achieving high-contrast, low-loss, multi-level modulation suitable for photonic memories and neuromorphic computing.

Contribution

It presents a novel design of a hybrid mode interferometer with nearly equal power coupling and multilevel transmittance modulation using phase-change materials.

Findings

Achieves nearly 14 dB contrast in transmission

Insertion loss below 0.1 dB in crystalline state

Enables multi-bit storage and phase shifting

Abstract

We propose a novel hybrid mode interferometer (HMI) leveraging the interference of hybridized TE-TM modes in a silicon-on-insulator (SOI) waveguide integrated with a GeSe phase change material (PCM) layer. The SOI waveguide's dimensions are optimized to support the hybridization of the fundamental transverse magnetic ($TM_0$) and the first higher transverse electric ($TE_1$) mode. This design allows for efficient and nearly equal power coupling between these two modes, resulting in high-contrast interference when starting from the amorphous PCM state. The PCM's phase transition induces a differential change in the modal effective index, enabling high-contrast transmittance modulation. Our numerical simulations demonstrate a multilevel transmission with a high contrast of nearly 14 dB, when the amorphous region's length is varied incrementally, enabling multi-bit storage. The transmittance is maximized in the fully crystalline state with an insertion loss below 0.1 dB. The HMI can also operate as a quasi-pure phase shifter when partially amorphized, making it suitable for Mach-Zehnder interferometers. These characteristics make the proposed device a promising candidate for applications in photonic memories and neuromorphic computing.