Modeling of optical modulator based on silicon by using germanium antimony telluride (GST) nanolayer in elliptical cylindrical waveguide structure

Abstract

This study introduces a high-performance silicon-based optical modulator that utilizes a germanium-antimony-telluride (GST) nanolayer within an elliptical cylindrical waveguide structure. By exploiting the phase-change dynamics of GST and engineered hybrid eHE_11 and oHE_11mode confinement, the device achieves an ultralow insertion loss of 0.15 dB, a remarkably high extinction ratio of 30.28 dB" " at a wavelength of 1550 nm for the fundamental eHE_11mode. The elliptical geometry enhances light-matter interaction through anisotropic mode confinement while improving thermal management, enabling a data bit rate of 13.33" Mb/s" via sub-200" ns" dual-voltage electrothermal actuation (4 V for crystallization, 10 V for amorphization). The switch maintains high energy efficiency, consuming E_"SET" =12.227" nJ" and E_"RESET" =5.015" nJ" calculated across the entire device volume. Multiphysics simulations validate the design: the tuned GST thickness (40±10" nm" ) balances the switching speed and optical contrast, while gold electrodes enable localized Joule heating with minimal optical loss (0.1" dB/µm" ). These advancements position the proposed modulator as a promising candidate for high-speed optical interconnects and programmable photonic circuits, addressing the critical demands for low-loss, high-contrast, and robust integrated photonics.