Mapping of transmission spectrum between plasmonic and nonplasmonic single slits. II: nonresonant transmission

In our previous work, the similarity in resonant transmission properties for plasmonic and nonplasmonic 2D single slits can be realized by mapping their resonant wavelengths through waveguide dispersion. To further extend the mapping for nonresonant condition, complex reflection and transmission coefficients at the end faces of a semi-infinite slit are analyzed to reconstruct the whole transmission spectra. The complex reflection coefficients are found to be similar at the same effective wavelength for both the plasmonic and nonplasmonic cases. The spectrum reconstructed by a Fabry–Perot model matches the transmission spectrum of a nonplasmonic slit and can be transformed into that of a plasmonic case by wavelength stretching with plasmonic waveguide dispersion. The transmission cross section is bounded by λ/(πd). Width-dependent redshifts of the transmission spectrum are associated with effective capacitances at the slit end faces. The same mapping method applies for a single slit with substrate or periodic structure. Furthermore, the optical property of a plasmonic slit can be achieved by a nonplasmonic slit via dimensional scaling. The focusing lens effect of a plasmonic slit array can be mimicked by a nonplasmonic slit array with dimensional scaling. The unified transmission properties of plasmonic and nonplasmonic 2D single slits can simplify the design of slit structures for plasmonic applications.