Through-Silicon Ultrafast Laser Welding

Joining workpieces is an essential step in numerous industrial applications. In contrast to many traditional methods, ultrafast laser welding offers the possibility to join workpieces in a fast, clean and contactless way. This method relies on the propagation of ultrashort pulses in a first workpiece, and energy deposition at the interface with a second workpiece. While it can be employed in configurations where the first workpiece is a dielectric material, it cannot be straightforwardly applied for a first workpiece made out of silicon (e.g., silicon-metal, silicon-silicon). This originates from nonlinear propagation effects which dramatically diminish the energy deposition at the interface [1-4]. Among these effects related to filamentation which cause strongly delocalized energy deposition, one must cite phenomena such as intensity clamping and nonlinear focal shift.