Third-order nonlinearity of metal nanoparticles: Isolation of instantaneous and delayed contributions

Measurement of transient absorption of a sample allows estimation of the evolution of the nonlinear response of materials after excitation by a short pump pulse. In this work, the time dependent nonlinear response of silver nanoplatelets in water was measured using transient absorption technique for various volume fractions of silver in water. These measurements were carried out in subpicosecond time scales and a suitable theoretical model was developed. It is been shown that the hot-electron contribution to the third-order nonlinearity of metal colloids is much higher than its instantaneous third-order nonlinearity. At low volume fractions, the delayed hot-electron contribution to third-order nonlinearity increases linearly with the volume fraction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766379]