Analysis and control of penetration depth fluctuations in single-mode fiber laser welds

Penetration depth fluctuations of single-mode fiber laser welds were studied and the effects of sinusoidal laser power modulations and circular focus spot oscillation were investigated. It was found that fiber laser welds had a high aspect ratio and penetration fluctuations tended to be larger for these deep, narrow welds. The weld penetration profiles had broadband, aperiodic power spectral densities with most of the signal power in the spectral band from 0Hz to 1kHz. The amplitude of the frequency response of the laser penetration to large amplitude laser power modulations decreased at rates varying from -20db/decade to - 60dB/decade as modulation frequencies increased from 100Hz to 1kHz. It was found that sinusoidal laser power modulation in a range of frequencies decreased the aperiodic penetration fluctuations. Welds were also made with linear travel and superimposed circular oscillations having a range of rotational frequencies and diameters using a galvanometer scanner. Oscillation parameter ranges...