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

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 sev eral meters. No damage is observed neither inside the fiber nor at its surf ace. The transmitted pulses are focused to a diameter of 700 mu m onto a wa ter-immersed type 304 stainless steel sample for laser shock processing. Wi th a pulse density of 10000 pulses/cm(2) a compressive residual surface str ess is achieved. The affected depth is almost 900 mu m, the maximum compres sive stress -700 MPa.