Appendix 2—figure 1. Three-dimensional finite-difference time-domain simulations of the electric field intensity distribution ${\displaystyle |\mathrm{E}{|}^2}$ in units of ${\displaystyle V^2/m^2}$ in the proximity of the zero-mode waveguides (ZMW) for excitation by a diffraction-limited focused Gaussian beam with wavelengths of 488 nm (A) and 640 nm (B).

The lower side of the 100-nm-thick palladium membrane is placed at z = 0 nm. The source is located at the bottom and the electric field is polarized in the x-direction. The electric field intensity distributions are shown for pores with a diameter of 50 nm, 100 nm, and 200 nm (from top to bottom) in the xz (left) and yz (middle) planes passing through the center of the pore, and the xy (right) plane at the entrance to the pore at z = 0 nm. See Appendix 2—figure 2 for a zoomed-out representation of the intensity distribution.