Studies of Two-photon Absorption in Heavy Metal Oxide Based Glasses

A serial of glass samples in Bi2O3-B2O3-SiO2 ternary system with high heavy metal oxide (Bi2O3) content were prepared by using conventional melting technique. Their linear refractive indexes n at 632.8nm were measured by prismcoupler, it showed that the n values were ranged from 1.9 to 2.1, and increased with increasing Bi2O3 content which was due to the high polarizability of Bi 3+ ions; their linear absorption spectra were depicted by spectrophotometer, and the optical band gaps Eopg were in the range from 2.229eV to 2.268eV while exhibited decreasing tendency with increasing Bi2O3 content. By employing open apertured Z-scan measurements at various wavelengths (770, 800, and 850nm), nonlinear absorption coefficients β which were due to twophoton absorption (TPA) since the incident photon energy hv (1.61, 1.55, and 1.46eV) of measured wavelengths were between Eopg/2 and Eopg of all samples studied were obtained. The results showed that the glass sample with lowest Bi2O3 content exhibited highest TPA coefficients ((3.6~6.1)×10 -12 m/W) which indicated as resonatetype induced by gap state at all measured wavelengths, demonstrating the sample can be applied in optical limiter. On the other hand, glass samples with higher Bi2O3 content showed offresonatetype TPA only at low wavelength of 770nm, and their TPA coefficients β increased with Bi2O3 content leading to the great potentials in all-optical switching (AOS).