Study on the non-linear refraction of silver nanoparticles with aggregation effect

The non-linear refractive responses of a highly monodisperse 10.5 nm diameter silver nanoparticles with the addition of KNO3 have been measured by Z-scan technique with 35-ps pulse-duration laser pulses at 1064 nm. Strongly enhanced non-linear refractions are observed by four times in the presence of KNO3. Through the size distribution and transmission electron microscopy measurements, the morphology of the aggregated silver nanoparticles has been observed as a chain-like aggregation. The dramatically enhanced non-linear refractive response was explained by the enhanced electromagnetic field near the surface of the silver nanoparticles as they approached.