Large electrooptic modulation in a thermally-poled germanosilicate fiber

A large linear electro-optic phase shift observed in a germanosilicate fiber has been induced by thermal poling at about 250/spl deg/C for 20-60 min with an electric field of >8/spl times/10/sup 5/ V/cm and a 3.3-cm electrode length. Polarization dependence of the V/sub /spl pi//L product in a birefringent germanosilicate fiber has been found, and the lowest V/sub /spl pi//L product has been measured for TE-polarization of 224 V/cm at 633 nm. Furthermore, it has been found that the electrical resistance between the electrodes is reduced by thermal poling.>