We report on the refractive index modification (Delta n) and its cross sectional profile of the created lines inside the different types of optical glasses, containing BaO, TiO2, or La2O3 as a metal oxide. The lines were fabricated by scanning a stage and focusing the femtosecond laser pulses, 800nm wavelength, a 250 kHz repetition rate and 200 fs pulse duration, from the Ti: sapphire regenerative amplifier system. The Delta n measurements were performed with the qualitative phase microscopy technique. As a result, it was found that the Delta n and its sign are different depending on glass types. For example, in the glasses containing TiO2, the Delta n became smaller in the modified region and some of them showed relatively large decrease of the Delta n, Delta n <-0.01, with about 10 mu m width. Such a glass material could be useful for the compact optics and optical devices. (C) 2010 Elsevier B.V. All rights reserved.