Study and development of high peak power short pulse Nd：YAG laser for peening applications

Because short pulse Nd：YAG laser of nanosecond pulse-width and high peak power has a unique capability to improve the mechanical properties of metal parts, a study on the development of high peak power short pulse from Nd：YAG laser along with its peening application has been performed. The design scheme of laser and the characteristic of laser beam transmission are presented and discussed. A pulse energy of 25 J with 15 ns pulse-width and a maximum peak power of 1660 kW laser system which use one oscillation and eight amplifiers has been achieved. Laser beam has a max divergence angle of 0.03 mrad, a pulse-to-pulse pulse-width stability of ＋0.1 ns, and the pulse-to-pulse energy stability factors of less than ±2.8%. A low value of divergence means an easier modification of a nearly hat-top laser beam intensity profile and an easier transmission of laser beam. To evaluate the performance of the laser system, several metal materials are processed. Laser peening quality and effi- ciency are analyzed by using an optical microscope, a transmission electron microscope, and an X-ray diffraction device. The processing results show that the performance of this laser system is excellent.