Laser shock processing with 20 MW laser pulses delivered by optical fibers

Abstract

A large-core multi mode optical fiber is used to deliver 100 mJ, 5 ns laser pulses produced by a frequency-doubled Nd:YAG laser over a distance of several meters. No damage is observed neither inside the fiber nor at its surface. The transmitted pulses are focused to a diameter of 700 μm onto a water-immersed type 304 stainless steel sample for laser shock processing. With a pulse density of 10000 pulses/cm2, a compressive residual surface stress is achieved. The affected depth is almost 900 μm, the maximum compressive stress −700 MPa.