Modeling of Optical Modulator based on Silicon by Using Germanium Antimony Telluride (GST) Nanolayer in Elliptical Cylindrical Waveguide Structure

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 eHE01, oHE11, and eHE11 mode confinement, the device achieves an ultralow insertion loss (0.22 dB), high extinction ratio (8.0 dB), and energy-efficient operation (2.91 nJ/bit) at a wavelength of 1550 nm. The elliptical geometry enhances the light-matter interaction through anisotropic mode confinement while improving thermal management, enabling sub-200 ns switching via dual-voltage electrothermal actuation (4 V for crystallization, 10 V for amorphization). 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 energy-efficient integrated photonics.