Characteristics of Plume Sound in Nd: YAG Laser Dirlling

Abstract

In order to obtain the fundamental characteristics of the plume sound induced during Nd : YAG laser drilling, the relationship between the sound pressure level and laser oscillating method, laser processing conditions were investigated and the frequency spectrum analysis was also done. The sound pressure waveform and frequency spectrum relate to the oscillating method, that is to say, the frequency spectrum, which is induced by Q-switch laser, consists of continuous spectrum such as white sound and n×f_Q (n: 1, 2, 3, …, f_Q : Oscillating frequency of Q-switch laser), the one induced by CW laser, contains only the continuous spectrum. The sound pressure level was influenced by laser processing conditions. Further, it could be estimated that the relationship between the sound power (W) and the reaction force (F_Pl) could be expressed as W∝F_Pl². Based on the results above, it can be expected that the useful informations about process monitoring can be obtained from the plume sound.