Solution by Pseudo-spectral time-domain method applied to Light scattering by hexagonal ice crystals

The pseudo-spectral time-domain (PSTD) method is used to solve Maxwell's equations. In this method, high order spatial derivatives are represented in terms of the fast Fourier transform (FFT). In contrast to the conventional finite-difference time domain (FDTD) method, PSTD is computationally more efficient since a coarse grid resolution (2-4 cells per wavelength) can be used in PSTD for acceptable accuracy. Thus, it appears feasible that PSTD can be applied to light scattering by nonspherical particles with moderate size parameters. We first validate PSTD by comparing with Mie theory for the case of spheres. Then, the PSTD method is utilized to compute the single scattering properties of nonspherical ice crystals. The results are then compared with the corresponding FDTD results at wavelengths of 0.66 µm and 11 µm.