Advances of Laser Welding Technology of Glass -Science and Technology-

Advances of laser welding technology of glass by continuous wave (CW), ns pulse, and ultrashort pulse (USP) lasers are overviewed in the past two decades from scientific and technological points of view. A novel thermal stress model shows that crack prevention in laser welding of glass depends on whether or not the molten pool has a free-surface. In glass/glass welding by CW laser, crack-freewelding is limited to glass having small coefficient of thermal expansion (CTE) due to the shrinkage stress, since the molten pool has a free-surface. In glass/glass welding by USP laser, crack-free-welding is available independently of glass's CTE if the gap between glass substrates is small, since nonlinear absorption process produces a molten pool having no free-surface so that the shrinkage stress is suppressed. Technical efforts to increase the bridgable gap without cracks using USP laser are demonstrated. In dissimilar welding of glass/metal (or glass/Si), successful weld joint can be obtained using ns and USP lasers by suppressing the melt splash of metal (or Si).