Abstract
Internal processing of glass was conducted by a femtosecond laser. The laser is irradiated repeatedly while the distance between pulses was kept constant. When the time interval of pulses was comparatively long, a narrow and long triangle-like pattern was obtained. On the other hand, a feather pen-like pattern was generated when the time interval is relatively short. It was estimated that the former pattern is obtained by two-photon absorption and the latter pattern is generated also by the temperature dependence of linear absorption coefficient due to heat accumulation effect. Validity of these estimations was confirmed by simple heat conduction analysis.
