Hello,

I would like to calculate the near-field frequency domain E field close to a silver sphere with 120nm diameter, with a electric dipole source. I noticed that there is an oscillation in my frequency results. I think these oscillations are numerical artifacts, because Generalized Mie theory produces the same major peak without any oscillations away from the peak. So I would really want to get rid of these oscillations in my FDTD calculations.

I’ve attached 2 calculations, one with 250-750nm test250-750nm.fsp (1.1 MB)

and one with 320-380nm test320-380nm.fsp (477.5 KB). The two calculations are basically the same, except that they use different material fittings: test320-380nm performs fit over the wavelength range of 250 to 450nm with an imaginary weighting of 15, while test250-750nm uses weighting of 1 over the range of 250 to 750nm. Both calculations show oscillations in E field (see Fig 1 for test250-750nm monitor 12 and Fig 2 for test320-380nm monitor 12).

Could anyone help me with this? Thank you very much.

Fig 1

Fig 2