Experimental study of Different Pulse Delay on thePhenomenon of Double Shock Wave Induced byMillisecond-nanosecond Combined-pulse Laser

We study the motion morphology, distance, and velocity of plasma and laser-induced shock waves induced by a millisecond–nanosecond (ms-ns) combined-pulse laser with different pulse delays on silicon. The laser shadowgraph method is used, and the phenomenon of double laser-induced shock waves has been found while the pulse delay is 1.2–1.8 ms. The controlling variable method is used to study this phenomenon, and it is found that it is mainly related to the ignition of the laser-supported absorption wave induced by the ms laser. Moreover, the plasma expansion velocity increases with the increase of pulse delay, the axial propagation distance of laser-induced shock waves increases monotonically with pulse delay, and the velocity of laser-induced shock waves decreases with the increase of pulse delay.