Nonresonant Optical Nonlinearities of Surface Chemically Modified ZnO Composite Nanoparticles

With surface chemical modification, we have obtained core-shell structure ZnO nanoparticles. The nonresonant third-order nonlinear optical refraction of this new composite material was found to be -3.8 x 10^-l0 esu by Z-scan measurements with a femtosecond pulsed laser. The ultrafast nonlinear response time ~250 fs measured by time-resolved pump-probe techniques suggests that the nonlinearity of this new material originates mainly from a rapid electronic polarization process or virtual process such as the optical Stark effect.