Analysis of Nitrides- and TCOs-Based Plasmonic Waveguides for Slow-Wave and Negative Index Sub-Wavelength Propagation

In this paper, a comparison between metal-insulator-metal (MIM) waveguides made of silver and newly emerging plasmonic materials is reported. In particular, titanium nitride (TiN) from the class of nitrides, and gallium zinc oxide (GZO) from the class of transparent conducting oxides, are proposed as alternatives to conventional metals for the more flexible exploitation of plasmonic properties. Depending on the specific application, the new choices of the plasmonic material allow for tuning of the surface plasmon resonance and may also reduce typical conductive losses. Moreover, compared to noble metals, these new plasmonic materials have the extremely important property of being compatible with the mature CMOS technology. In this paper, the specific application of MIM waveguides made of TiN and GZO for dispersion engineering (slow-wave propagation and negative effective index) is considered for the first time.