Multiple Extraordinary Optical Transmission Peaks via a Single Subwavelength Slit Surrounded by Mixed-Period Grooves

In this paper, we use mixed-period grooves to surround a subwavelength slit to realize multiple extraordinary transmittance peaks for transmitted light. The mixed-period grooves refer to a set of 1-D grooves arranged with particular groove pitches, which are formed by merging two sets of 1-D periodic grooves with similar geometries but mainly different groove periodicities. The finite-difference time-domain method was used to calculate the transmittance spectra for the proposed mixed-period slit-groove structure over the visible regime. The calculated spectra show that the mixed-period grooves could induce dual groove-generated extraordinary transmission peaks in the visible regime. We find that the mixed-period grooves can act as a grating coupler to excite surface plasmon polaritons at multiple incident wavelengths. Moreover, one approach has been presented to further boost the transmission at the dual groove-generated peaks.