Sketch of the periodic slit array illuminated by p-polarized light. Slits are infinitely long in the y-direction. Contour C is intended for the enhancement estimation Eq. (2) in the static regime.
FDFD simulations of components (a) and (b) of the electric field, absolute values of (c) the magnetic field and (d) the Poynting vector near the 10-nm-wide slit of thickness h = 50 nm in a gold grating with a period of at a frequency f = 0.01 THz resulting in G = 100. Bounds for color maps are chosen so to show better peculiarities of field distribution. (e) Profiles of the electric field component in different slits, all giving enhancement of 100. Parameters of gratings are given in the legend. (f) Mesh refinement (thin, grey lines) at the metal-slit boundaries (thick, black lines).
(a) Enhancement factor G (see Eq. (12)) for different slit widths (compare with numerical simulation in Fig. 6(a)). (b) Enhancement factor for slit-average field G and field at the slit center , if 2M slits act on the slit under consideration. In the inset, the long periods P approaching to the wavelength are considered. Enhancement factor versus (c) slit width and (d) metal thickness.
Evolution of transmission spectra with period P for thin metal films (w = h = 20 nm). Spectra are calculated for the homogenized material with dielectric permittivity (28).
(a) Field enhancement and (b) transmittance of 10-nm-wide slits cut in a 20-nm-thick film versus frequency for different grating periods P (FDFD simulation). The enhancements in the quasi-static limit are chosen to be , where A changes from 2 to 10 and B from 0 to 3 (increment is 1 both for A and B). The period of the grating is P = wG. (c) The dependence of the enhancement on the dimensionless parameter for a single slit (h = 20 nm). Each line is obtained by varying at some slit width w, so that a total of 23 curves are plotted for a set of 23 slit widths (taking values between 10 nm and ). For all the curves, the incident wavelength is changed from to corresponding to the frequency range between and
(a) Enhancement G and (b) transmittance T in gratings with periodicity and varying slit width w = P/G given by the following approximate set of numbers in nm: 400.0, 200.0, 100.0, 66.7, 50.0, 40, 33.3, 28.6, 25.0, 22.2, and 20.0, which correspond to enhancements 50 and 100 to 1000 with the increment 100 within the plateau zone (FDFD simulation). (c) Detailization of several curves for the enhancement from (a) on a logarithmic scale. Lines with open circles correspond to the enhancement in isolated slits of the same widths as indicated in the legend.
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