Enhanced nonlinear optical properties of oxygen deficient lead-niobium-germanate film glasses

Abstract

The third order nonlinear optical properties of oxygen deficient lead-niobium-germanate film glasses with heavy metal contents beyond that of the bulk glass formation region have been investigated. Values of the nonlinear third order optical susceptibility up to /χ(³)/ ≈ 1.8×10⁻¹¹ esu have been measured by degenerate four wave mixing at 800 nm in films having large heavy metal fractions (0.93). The fast buildup and decay times ( ≈ 130 fs) of the nonlinear response confirm its nonresonant character. The partial reduction of Nb⁵+ to Nb4+ evidenced by x-ray photoelectron spectroscopy, which is associated with the oxygen deficiency, appears to be responsible for the strong enhancement of /χ(³)/.