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A new technique has been developed for creating multiscale micro/nanoscale surfaces on metals. This technique is based on past work in femtosecond laser surface processing (FLSP) and dual pulse laser induced breakdown spectroscopy (LIBS). Using a femtosecond laser, pulse pairs were created with varying pulse separations between 0 ps to 500 ps. The creation of surface structures with dual pulse FLSP was studied on Ag, Cu, Ti, Al, Ni, and 304 stainless steel in relation to pulse separation.
Using dual pulse FLSP micro/nano structures have been created for the first time on silver. The silver structures are multiscale in nature with an average height of 32 μm and a nanoparticle aggregate covering them. This dual pulse method also reduces the needed fluence to create micro/nano structures on copper when compared to FLSP performed with a single pulse train. It was found that the formation of these surface structures is dependent on the pulse separation between pulse pairs. The initial pulse temporarily decreases the material reflectivity which causes increased absorption of the second pulse. The reduction in reflectivity increases the laser energy being coupled into the material.
Advisor: Dennis Alexander