TiO2

Titanium Dioxide is well-known as the highest index materials for the visible region. TiO2 can provide a durable protective coating used in multi-layers for laser mirrors, beam splitters, cold mirrors and heat reflecting mirrors.

Titanium oxides have some other stoichiometries, TiO, Ti2O3, Ti3O5, Ti5O9, Ti4O7, etc. All of these substances can be evaporated and subsequently oxidized to the final stable phase: TiO2.