Second harmonic generation from bulk glassceramics containing laser-poled dielectric nanocrystals

Silica glass with SnO2 nanocrystals, obtained from sol-gel synthesis and thermal densification at 1100 °C, was poled by means of a two-step process consisting of infrared 1064 nm laser irradiation followed by 532 nm laser exposure in high-voltage static electric field. Maker fringe experiments were then carried out at 1064 nm. The results show the formation of second-order nonlinearity with macroscopic nonlinear thickness (about 1 mm) and nonlinear susceptibility comparable with thermally poled silica (about 0.1 pm/V). Photoluminescence measurements suggest that mechanisms for this process should involve the activation and anisotropic ionization of defects at the interface between nanocrystals and glass.