ENHANCEMENT OF OPTICAL NONLINEARITY OF HEAVY-METAL OXIDE GLASSES BY REPLACING LEAD AND BISMUTH WITH THALLIUM

We report on the results of degenerate four-wave mixing experiments at a wavelength of 1.06 mum on a number of heavy-metal gallate glasses. The replacement of lead (Pb) and/or bismuth (Bi) by thallium (Tl) lead s to an enhancement of the optical nonlinearity, resulting in the larg est nonresonant electronic nonlinearity yet reported for an oxide glas s. Chi(3) is proportional to the concentration of Tl; samples with mor e than 25 cation % Tl have chi(3) larger than that of carbon disulfide (CS2). The optical nonlinearity has afl off-resonant electronic origi n, which is confirmed by measurements of the diagonal and off-diagonal components of the chi(3) tensor.