Two-layer model for light transmission through a nanostructured metallic subwavelength slit.
The schematic supercell configuration of a general metallic layer under the TMM simulation. The supercell consists of air domains and each has its own EM field modes. These modes are used to construct the transfer matrix between the incoming and outgoing EM fields.
Calculated contour plot of angle transmission distribution of a nanostructured metallic slit. The overall thickness of the slab is and the width of the central slit is 400 nm. The groove pattern has a period of , a depth of , a width of 400 nm, and there are 10 grooves on both sides. There are four lines on the plot, which represent four kinds of coupling method between surface wave and grating.
Four coupling methods between surface wave and surface corrugation grating. This figure explains why there are four lines on the contour plot of Fig. 3.
Calculated angular diffraction distribution plots of structures with different periods. As the period of the grating gets larger, more coupling methods appear because more reciprocal vectors are needed for coupling with the surface waves. The period of the structures is 5.0, 5.5, 7.0, 7.5, 8.0, and for panels (a)–(f), respectively. The other geometrical parameters of the structures are the same as Fig. 3.
Calculated diffraction pattern [panels (a) and (c)] and angular transmission distribution [panels (b) and (d)] of an incident -polarized light scattered by two nanostructured metallic slits, slit 1 [ panels (a) and (b)] and slit 2 [panels (c) and (d)]. Slit 1 has a groove period of and generates one well-collimated beam at wavelength , while slit 2 has a groove period of and generates two well-collimated beams at wavelength . In panels (a) and (c), the coordinates are all in unit of micrometer.
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