NONLINEAR-OPTICAL PROPERTIES OF B2O3-BASED GLASSES - M(2)O-B2O3 (M=LI, NA, K, RB, CS, AND AG) BINARY BORATE CLASSES

The third-order nonlinear optical susceptibilities chi((3)) of M(2)O-B2O3 (M = Li, Na, K, Rb, Cs, and Ag) binary borate glasses have been measured by the third harmonic generation (THG) method. It is found that the enhancement of chi((3)) by the structural change of BO3, units to BO, units is small, while the enhancement of chi((3)) due to the formation of nonbridging oxygen is rather significant. The effects of alkali cations on the chi((3)) of alkali borate glasses are discussed in terms of the M-O bond character, focusing on the covalency of Li2O-B2O3 glasses. Comparison of the chi((3)) values for Cs2O-B2O3 and Ag2O-B2O3 glasses which contain cations of comparable polarizability reveals that the chi((3)) value is much greater for Ag2O-B2O3 glasses than for Cs2O-B2O3 glasses, which is possibly due to the great contribution of Ag(4d(z2) + 5s + 5p(z)) hybrid orbitals to the nonlinear optical response.