  ZnO nano particles are synthesized at different percentages of Ag dopant by
facile precipitation method. Two photon absorption (2PA) cross-section and
nonlinear refractive index of ZnO nano particles are studied with 130
femto-second laser pulses at a repletion rate of 1 kHz with central wavelength
of 532 nm by z-scan technique. The 2PA cross-section of ZnO nano particles are
obtained by theoretical calculations, using rate equation approach. Both
absorption cross-section and nonlinear refractive index increased with
increasing the Ag dopant percentage. We have observed an increase of order of
104 in the nonlinear refractive index in the presence of femto-second laser
excitation with reference to nano-second laser excitation.
