Ultrafast response of nonlinear refractive index of silver nanocrystals embedded in glass

Ultrafast Kerr-type nonlinearities and relaxation dynamics of photoexcited electrons in silver nanocrystals embedded in glass have been investigated b y means of femtosecond pump and probe spectroscopy. The transient absorptio n spectrum induced by the surface plasmon excitation shows a redshift and b roadening of the surface plasmon band. The additional broadening is ascribe d to the increase of surface plasmon damping and the redshift originates fr om a change in the real part of the dielectric function of the silver nanoc rystals due to nonequilibrium electron heating. The observed redshift yield s the nonlinear refractive index n(2) of +2.4x10(-10) esu and its time resp onse is 1.9 ps. (C) 1999 American Institute of Physics. [S0003-6951(99)0193 8-5].