Second order optical non-linearity of transparent glass-ceramic materials induced by alternating field

The optical non-linearity of transparent glass-ceramic materials in K2O–Nb2O5–GeO2 and K2O–Nb2O5–TeO2 systems has been investigated using electric-field-induced second harmonic (EFISH) and Maker fringe techniques. For the tellurite glass-ceramics, which show an SHG property without any electric treatment like thermal poling, the SH signal is relatively low and insensitive to the applied field. On the other hand, the germanate glass-ceramics consisting of nanocrystalline K3.8Nb5Ge3O20.4 phase have a good transparency, and the apparent susceptibility of second order non-linearity is linearly increased with instantaneous applied field of various frequencies up to 1 kHz. The non-linearity constant corresponding to the third-order χ(3) is estimated by Maker fringe profiles and increased by three times after nanocrystallization over the precursor glass.