Geometry of the energy input of a shockwave generated by a nanosecond laser-induced breakdown

Abstract

Abstract The spatio-temporal evolution of the shock wave generated by a laser induced breakdown is often investigated and interpreted in the framework of the theory of shock similarity solutions. This work is a discussion about the choice of the most relevant geometry (spherical or cylindrical) to be used in the Jones modelling to track the intermediate-strength shockwave trajectory coming from a laser-induced non-resonant breakdown in argon. Laser incident energies ranging from 10 to 200 mJ with initial pressure of argon from 250 to 2500 mbar are investigated using a Q-switched Nd:YAG laser operating at a wavelength of 532 nm with a 6 ns pulse duration. Experimental results show that using the radial component r b of the ellipsoidal shape of the shockwave with a cylindrical geometry best describes the shockwave trajectory over time. Moreover, the deduced characteristic length r 0 allows us to observe a shockwave shape similarity for all tested laser energies at a given pressure.