Impact of GST thickness on GST-loaded silicon waveguides for optimal optical switching

Phase-change integrated photonics has emerged as a new platform for developing photonic integrated circuits by integrating phase-change materials like GeSbTe (GST) onto the silicon photonics platform. The thickness of the GST patch that is usually placed on top of the waveguide is crucial for ensuring high optical performance. In this work, we investigate the impact of the GST thickness in terms of optical performance through numerical simulation and experiment. We show that higher-order modes can be excited in a GST-loaded silicon waveguide with relatively thin GST thicknesses (<100 nm), resulting in a dramatic reduction in the extinction ratio. Our results would be useful for designing high-performance GST/Si-based photonic devices such as non-volatile memories that could find utility in many emerging applications.