Split Ring Resonator (SRR) based metamaterials

Abstract Metamaterials are artificial materials that are known to produce extraordinary electromagnetic responses due to their constituent artificially-engineered micro- or nanostructures of dimensions smaller than that of the wavelength of light. The Split ring resonator (SRR) is such a nanostructure that forms the basic unit of a metamaterial. Since the dimensions of the SRRs are required to be smaller than the resonance wavelength, it becomes critical when response is required at the near infrared and optical wavelengths. In this thesis the various properties of the nanoscale SRRs are studied that resonates in the infrared and visible spectrum. The SRRs mentioned in this thesis are made of both aluminium and gold and have been fabricated on silicon and silica substrates using standard electron beam lithography (EBL) techniques. The effect of different metals (Al and Au) on the resonance of SRRs is studied. A substantial shift is reported, in the response of arrays of similarly sized SRRs, made respectively of aluminium and of gold. It is shown that by using aluminium based SRRs instead of gold; the magnetic resonance of SRRs can be shifted into the visible spectrum. The effect of titanium adhesion layers on the properties of SRRs are considered and it is shown that even a 2 nm thin layer of titanium can red-shift the SRR resonance by 20 nm. It is shown, that by adding asymmetry between the geometries of similar sizes SRRs, it is possible to produce a steeper resonance response, thereby increasing the quality factor of the SRRs. This steep response of asymmetric split ring resonators (A-SRRs) are utilised for the optical detection of very thin film organic compounds. It is further shown that by localising the organic compound to specific regions of the A-SRRs, greater enhancement in optical detection could be achieved. Finally, the same property of A-SRRs are utilised for the enhanced detection and differentiation between different DNA strands