Abstract
Due to their extremely high peak intensity, ultrashort laser pulses can readily initiate the multi-photon
process at the focal point inside transparent materials and directly and precisely join them via localized
melting without any intermediate layer under a room-temperature environment. These features are well
fi tted for the hermetic sealing of such photonics devices as solar cells, LCDs, and MEMS. We review
the recent advances of the welding or joining of glass substrates with an ultrashort laser micro (ULM)
joining technique. After briefl y discussing its principles, we address such critical issues of it as the pulse
repetition rate, the use of the fi lamentary propagation of pulses, residual stress, glass-metal joining, the
joined glass-metal interface, and the temperature dynamics. Finally, we introduce trial applications to
industrial solar cell panels and the glass-Si wafer joining.
