Abstract
Previous reports of ultrafast laser welding of glass-to-glass have indicated that a pre-existing optical contact (or very close to) between the parts to be joined is essential. In this paper, the capability of picosecond laser welding to bridge micron-scale gaps is investigated, and successful welding, without cracking, of two glasses with a pre-existing gap of 3 µm is demonstrated. It is shown that the maximum gap that can be welded is not significantly affected by welding speeds, but is strongly dependent on the laser power and focal position relative to the interface between the materials. Five distinct types of material modification were observed over a range of different powers and surface separations, and a mechanism is proposed to explain the observations.
Highlights
Ultrafast laser welding has received significant attention due to its highly localized heating [1,2,3], coupled with the ability to join optically transparent materials
In order to join two transparent materials with conventional laser welding, an optically-absorbing intermediate layer is required [1]. This layer is not necessary with ultrafast laser welding, since it is enabled by the nonlinear absorption of the laser radiation due to high peak power of the laser pulses
We have carried out welding of two glass parts with a controlled gap, either by using a sample with a curved surface together with a glass wafer, or two wafers, one which has a series of grooves etched into the surface
Summary
Ultrafast laser welding has received significant attention due to its highly localized heating [1,2,3], coupled with the ability to join optically transparent materials. In order to join two transparent materials with conventional laser welding, an optically-absorbing intermediate layer is required [1]. This layer is not necessary with ultrafast laser welding, since it is enabled by the nonlinear absorption of the laser radiation due to high peak power of the laser pulses. The highly localized nature of the nonlinear absorption means that welds can be created whilst avoiding excessive heating of the surrounding material – important for joining materials with significantly different thermal expansion coefficients [1,8]
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