Design Optimization of GeSn‐Based Structures for Efficient Mid‐Infrared Surface Plasmon Polariton Excitation and Propagation via Grating Coupling

Surface plasmon polaritons (SPP) are efficiently excited using various techniques, including prism coupling and diffraction gratings, to control the light–SPP coupling at the nanoscale. While typically excited at the metal–dielectric interfaces, the use of Gr‐IV materials offers special advantages, showing the compatibility for integration with existing semiconductor technologies. GeSn alloy has attracted much attention for its potential in various applications, particularly in integrating Si photonics with CMOS technologies. The bandgap tunability of the alloy allows it for use in IR applications, specifically in the mid‐IR range. Herein, SPP excitation using grating‐assisted coupling in GeSn heterostructure has been investigated using COMSOL MULTIPHYSICS Simulator. In particular, the study has taken into consideration rectangular, sinusoidal, trapezoidal, and triangular GeSn dielectric gratings to assess their performance and optimize the structural parameters to increase the efficiency of SPP generation. Performance analysis shows that over a wide excitation wavelength range of 3600–4100 nm, the rectangular grating achieves the highest power density (1.5 × 10 7 W m −2 ) and normalized magnetic field (530 A m −1 ). Critical information for the design of CMOS‐compatible mid‐IR plasmonic devices based on GeSn is provided by these results, which demonstrate the impact of grating geometry on SPP excitation efficiency.