Internal modification by ultrashort laser pulses (USLPs) has attracted much attention, which include waveguide formation, selective etching, microwelding and so on. Among them glass welding is, without any doubt, one of the most promising applications, since glass welding is extremely difficult due to brittle property despite its excellent physical and chemical properties.
Present talk consists of two parts. First part discusses laser absorption property of transparent dielectrics, which includes evaluation of nonlinear absorptivity and analysis of laser absorption process based on rate equation model. Second part includes crack-free welding mechanism, sample preparation for welding and mechanical strength of weld joint. High mechanical strength of glass-to-glass microwelding is shown to be realized at high throughput using USLPs at high pulse repetition rates. High speed, high strength glass-to-Si welding is also presented, which is competitive to anodic bonding technology.