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Plasmonics has long been seen as a promising technology for integrated optical devices for many fundamental applications such as telecommunications, chemistry, quantum science, and medicine. However, for these devices to be realized in a large scale, they should be CMOS-compatible – a problem for plasmonic devices which have generally relied on noble metals. Recently, CMOS compatible materials titanium nitride and transparent conducting oxides (such as doped zinc oxide) have been proposed as the most promising materials for telecommunication applications. TiN is a gold-like ceramic material with a permittivity cross-over near 500 nm. In addition, TiN can attain ultra-thin, 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. In fact, similar designs using TiN have outperformed gold waveguides due in large part to the reduced scattering loss of epitaxial quality films. Utilizing highly doped zinc oxide films as a dynamic photonic material, high performance modulators can also be realized. Together, these alternative materials form the base of a fully integrated nanophotonic system, capable of exceptional performance with speeds greater than 1 THz, in large part due to the development of alternative materials. Consequently, nanophotonic technologies are reaching a critical point where many applications including telecom, medicine, and quantum science can see practical systems which provide new functionalities.
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