Polarization selectable nonlinearities in elongated silver nanoparticles embedded in silica

The size, shape and composition of nanoparticles in a composite become design parameters that can be manipulated to enhance the third-order nonlinear response of the composite. In this work we report the study of the nonlinear response of a composite material consisting of elongated silver nanoparticles that are aligned in a preferential direction. The absorptive and refractive contributions to the nonlinear response of the sample were studied using the Z-scan technique with 80 fs pulses at 825 nm. The nonlinear response was studied as a function of the intensity, and the polarization angle of the light. A large anisotropy was observed in both the refractive and absorptive contributions to the nonlinearity. The fast electronic, and slow thermal contributions to the nonlinear response were resolved by conducting experiments using a chopper to change the thermal load to the sample, while maintaining a constant peak irradiance. The results were compared with the nonlinear optical response of spherical silver nanoparticles.