Third-order optical nonlinearities and their ultrafast response in Bi_2O_3–B_2O_3–SiO_2 glasses

Nonresonant-type homogeneous Bi2O3–B2O3–SiO2 glasses were prepared by melting. The third-order optical nonlinear susceptibility χ(3), which was determined by measurement of third-harmonic generation, increased with increasing concentrations of Bi2O3 in the glass. The maximum χ(3) estimated was 9.3×10-12 esu in glass that contained 92 wt. % of Bi2O3.χ(3) values of these glasses were enhanced by the small optical bandgap. These glasses also exhibited an ultrafast response time, less than 200 fs, when a degenerate four-wave mixing method with a femtosecond laser was used, indicating that the nonlinearity of these glasses originated mainly from pure electronic polarization.