Ultrafast laser microwelding for transparent and heterogeneous materials

When ultrafast laser pulses are focused inside the interface between a couple of transparent materials, the optical intensity in the focal area can usually become high enough to initiate the filamentary propagation of optical pulses and almost simultaneously the nonlinear absorption occurs in the filamentary area. Due to this absorption of optical energy, both of the materials can locally be melted and the interface is joined after resolidification. The laser microwelding technique based on the nonlinear phenomena has several unique features: (i) the insertion of any intermediate layers is no need for the microwelding, (ii) it's possible to weld the materials with different thermal expansion coefficients, (iii) the joint area can also be arbitrarily extended by scanning the filamentary area. We call this powerful technique "ultrafast laser microwelding". In this paper, we present the results on "ultrafast laser microwelding" for transparent materials such as the silica and borosilicate glass, and heterogeneous materials such as glass and metals.