Implementing the near- to far-field transformation in the finite-difference time-domain method

Area of Science:

• Computational electromagnetics
• Light scattering physics

Background:

• Finite-difference time-domain (FDTD) is used for light-scattering computations.
• Near-to-far field transforms are essential for obtaining far-field scattering properties.

Purpose of the Study:

• To investigate and compare the accuracy of near-to-far field transform methods for light scattering by spheres using FDTD.
• To analyze the impact of refractive index on the performance of surface and volume integral approaches.

Main Methods:

• Utilized rigorous Lorenz-Mie theory to compute accurate near-field components on FDTD-staggered meshes.
• Applied both surface-integral and volume-integral approaches for near-to-far field transformation.
• Investigated canonical scattering problems involving spheres with varying refractive indices.

Main Results:

• For small refractive indices, surface integrals are more accurate for phase functions and extinction efficiencies.
• Volume integrals show higher accuracy for specific scattering matrix elements (P12, P32, P43), particularly in backscattering.
• Volume integration accuracy decreases with high refractive indices, while surface methods maintain accuracy.

Conclusions:

• The choice between surface and volume integral methods for near-to-far field transformation in FDTD depends on the scattering properties of interest and the material's refractive index.
• Surface integral methods offer robust accuracy across different refractive indices for certain scattering parameters.
• Volume integral methods are advantageous for specific scattering matrix elements but are sensitive to high refractive indices.