Structural optimization of integrated non-volatile photonic memory towards high storage density and low energy consumption

Abstract

Photonic memory provides optics the opportunity for upgrading data storage hardware and shows great promise in future computing hardware due to its innate superiority in speed, power consumption and bandwidth. Chalcogenide phase-change materials (PCMs) such as Ge2Sb2Te5 (GST) are one of the most promising non-volatile storage materials and have been used for on-chip photonic integration circuits (PIC). Here, we explore the transmission contrast and the thermal distribution produced by different spatial structures of GST cells in photonic memory including geometric shapes, vertical positions and array distributions. We design the geometric shape of GST cells in photonic memory that matches the optical field distribution profile, causing a more than 20% increase in transmission contrast. We then set the vertical position of GST cells embedded in waveguides where the GST cell is overlapping most with the waveguide propagation mode, increasing the transmission contrast by more than 50%. Engineering the surrounding cladding layer is also an effective method to improve the transmission contrast (>10%). Beyond that, selecting a suitable size of the gap can obtain a better balance between the storage capacity and the thermal management in uniform GST arrays while the non-uniform array can further improve the thermal uniformity. Our studies indicate that spatial distribution optimization of light storage media is necessary to develop low-energy-consumption on-chip PIC.