Alternative materials for practical plasmonics

Plasmonics has long been seen as a promising technology for integrated optical devices for many fundamental applications such as telecom, chemistry, quantum science, and medicine. However, large scale of integration relies on CMOS-compatibility – a problem for plasmonic devices that typically make use on noble metals. Recently, CMOS compatible metal nitrides and transparent conducting oxides have been proposed as very promising alternative material platforms. For instance, TiN is a gold-like ceramic material with a permittivity cross-over near 500 nm that can be shaped as ultra-thin, and ultra-smooth epitaxial films on substrates such as c-sapphire, MgO, and silicon. Partnering TiN with CMOS-compatible silicon nitride enables a fully solid state waveguide which is able to achieve a propagation length greater than 1 cm for a ~8 μm mode size at 1.55 μm. TiN-based plasmonic interconnects have outperformed gold waveguides due in large part to the reduced scattering loss of epitaxial quality films. Another example of alternative plasmonic compound is represented by highly doped zinc oxide, a dynamic photonic material that can be used for ultra-compact and high performance modulators. Together, these alternative materials form the base of a fully integrated nanophotonic system, capable of exceptional performance with operational frequencies in the THz regime.