Gold and silver resonators and their optical properties

We present fabrication and optical properties of sub-wavelength metallic structures, including the sub-100 nm size gold and silver split ring resonators (SRRs). It is shown that introducing rotational symmetry into SRR array could enhance the resonance magnitude of magnetic and electric modes under unpolarised light illumination, thus enabling SRR optical characterisation using simple unpolarised light. Sub-100-nm SRRs will be shown to have magnetic resonance entering in the visible frequency range, where silver SRR as small as similar to 60 nm had been successfully fabricated with fundamental magnetic resonance at similar to 604 nm. The resonance wavelengths of the LC and plasmon modes of the sub-100-nm SRRs are found to linearly decrease with the decrease of SRR size, suggesting that kinetic inductance has not yet occurred at such frequency and also the possibility of having shorter magnetic resonance wavelength.