Nonlinear refraction and two-photon absorption in dense 2Bi2O3-B2O3 glasses

High density transparent glasses (7.86 g/cc) were fabricated in the 2Bi2O3-B2O3 (BBO) system. Optical band gap of the obtained glasses was found to be 2.6eV. The refractive index measured for these glasses was 2.25±0.05 at λ=543 nm. Nonlinear refraction and absorption studies were carried out on the BBO glasses using z-scan technique at λ=532 nm of 10 ns pulse width. The nonlinear refractive index obtained was n2=12.1x10-14 cm2/W and nonlinear absorption coefficient was β=15.2 cm/GW. The n2 and β values of the BBO glasses were large compared to the other reported high index bismuth based oxide glass systems in the literature. These were attributed to the high density, high linear refractive index, low band gap and two photon absorption associated with these glasses. The electronic origin of large nonlinearities was discussed based on bond-orbital theory.