The key role of interband transitions in hot-electron-modulated TiN films

Titanium nitride (TiN) is an emerging new material in the field of plasmonics, both for its linear and nonlinear optical properties. Similarly to noble metals, like, e.g., gold (Au), the giant third-order optical nonlinearity of TiN following excitation with fs-laser pulses has been attributed to the generation of hot electrons. Here we provide a numerical study of the Fermi smearing mechanism associated with photogenerated hot carriers and subsequent interband transitions modulation in TiN films. A detailed comparison with Au films is also provided, and saturation effects of the permittivity modulation for increasing pump fluence are discussed.