Nonlinear Optical Properties of B ₂ O ₃ ‐Based Glasses: M ₂ O‐B ₂ O ₃ (M = Li, Na, K, Rb, Cs, and Ag) Binary Borate Glasses

Abstract

The third‐order nonlinear optical susceptibilities χ (3) of M 2 O‐B 2 O 3 (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 χ (3) by the structural change of BO 3 units to BO 4 units is small, while the enhancement of χ (3) due to the formation of non‐ bridging oxygen is rather significant. The effects of alkali cations on the χ (3) of alkali borate glasses are discussed in terms of the M‐O bond character, focusing on the covalency of Li 2 O‐B 2 O 3 glasses. Comparison of the χ (3) values for Cs 2 O‐B 2 O 3 and Ag 2 O‐B 2 O 3 glasses which contain cations of comparable polarizability reveals that the χ (3) value is much greater for Ag 2 O‐B 2 O 3 glasses than for Cs 2 O‐B 2 O 3 glasses, which is possibly due to the great contribution of Ag(4 d z2 + 5 s + 5 p z ) hybrid orbitals to the nonlinear optical response.