Fig. 1. Nanorectangle (NR) apertures milled in an aluminum film to concentrate the light at a subwavelength scale. (a and b) Scanning electron microscope image of some NR samples tested for the visible and UV experiments. All images have the same scale and 500 × 500 nm2 total dimensions. (c–f) Numerical simulations using finite-difference time-domain method of the electric field intensity enhancement within a plane located 10 nm inside the aperture (red wavelength (c and e)) or 5 nm (ultraviolet, (d and f)). Circular zero-mode waveguide (ZMW) apertures are shown in (e and f) to serve as reference. Throughout (c–f), the incoming light polarization is oriented vertically and perpendicular to the long axis of the NR.
