FDTD Simulation of Electromagnetic Field Distribution in Two-Dimensional Surface Plasmon Waveguide Structures

Finite-difference time-domain (FDTD) simulation provides an effective approach for analyzing electromagnetic field distributions in two-dimensional surface plasmon waveguide structures. This computational technique is particularly valuable in photonics research, where plasmonics continues to gain attention due to its capability for subwavelength light confinement and enhanced light-matter interactions. The FDTD algorithm implements spatial and temporal discretization of Maxwell's equations using central difference approximations, typically employing Yee's grid scheme where electric and magnetic field components are staggered in both space and time domains. Key implementation aspects include setting perfectly matched layer (PML) boundary conditions to absorb outgoing waves, defining material parameters through frequency-dependent permittivity models (e.g., Drude model for metals), and implementing field update equations through iterative time-stepping. The core computation involves solving coupled curl equations: ∇×E = -μ∂H/∂t and ∇×H = ε∂E/∂t, discretized using second-order accurate finite differences. For surface plasmon waveguides, the code typically initializes source excitation using dipole or waveguide mode sources, then propagates fields through the structure while recording field distributions at specific monitor points. Through systematic simulation of surface plasmon behavior across various waveguide geometries, researchers can quantitatively analyze propagation characteristics, mode confinement factors, and loss mechanisms, enabling optimized design of plasmonic devices for applications in sensing, communication, and integrated photonic circuits.