Fabricating metamaterials from subwavelength-sized meta-atoms becomes increasingly difficult as the operating frequency increases. Various methods can be applied to nanoscale structure fabrication, i.e., assuming we want features that are much smaller than the wavelength and we are operating in the infrared or visible part of the spectrum. In addition, material properties change at higher frequencies, as we saw when discussing the Drude model for a metal, which behaves much more simply above its plasma frequency. Advances in fabrication technologies are ongoing, so just a few more common techniques are presented here. There are many sources of information on these technologies, including those from equipment vendors, which provide more detailed information about what can and cannot be done. In this chapter we have drawn frequently from an excellent paper by Boltasseva and Shalaev, and we note a recent review by Yoon et al.
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