  This paper has presented inversely determining the resonant configuration of
the bilateral nanostructures for periodic metallic slits with extraordinary
optical transmission performance. The topology optimization approach is
utilized to implement the inverse design procedure. Several geometrical
configurations of the bilateral nanostructures are derived for periodic
metallic slits. The resonant performance of the derived nanostructures are
demonstrated by the transmission spectra, where the transmission peak is
presented at the specified wavelength in the inverse design procedure. This
provides an approach to control the red or blue shift of the transmission peak
or localize the resonant performance at a desired frequency, by specifying the
desired incident wavelength in the inverse design procedure. The inverse design
method is extended to make the periodic metallic slits to be less sensitive to
the incident wavelength. This research can be further extended to inversely
find the resonant subwavelength structures for extraordinary optical absorption
and other surface palsmon polariton based photonic devices. The inverse design
of three dimensional apertures for extraordinary optical transmission will be
investigated in our future researches.
