“…Near-field enhancement in nanogaps of various types leads to surface-enhanced Raman scattering (SERS) and strong light–matter interaction [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. This nanogap platform can also be used for constructing long wavelength polarizers, both negative and positive, which are related to the vector Babinet’s principle [ 40 , 41 , 42 , 43 ]. Decreasing the gap size makes higher field enhancement until the gap size becomes much smaller than the metallic film thickness; when the periodicity becomes much smaller than the wavelength; and when small gaps introduce quantum contacts between two metal planes [ 42 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ].…”