Delayed optical nonlinearity of thin metal films
  Metals typically have very large nonlinear susceptibilities, whose origin is mainly of thermal character. We model the cubic nonlinearity of thin metal films by means of a delayed response derived \textit{ab initio} from an improved version of the classic two temperature model. We validate our model by comparison with ultrafast pump-probe experiments on gold films. 
Matteo Conforti, Giuseppe Della Valle
physics.optics