This paper proposes a diagnostic technique to directly measure the 2-dimensional beam distribution in the focal area of a high-power and pulsed Nd3+:YAG laser for material processing. A rotating-pinhole laser beam analyzer combined with a signal-pulse generator was used to measure the intensity distribution of a 1.06 μm wavelength beam, while synchronizing the output of the pulsed laser with the motion of the pinhole. Some experiments were carried out with a Nd3+:YAG rod under thermal stationary conditions and results were obtained.
Reproducibility of measured beam intensity distribution is very good with high temporal and spatial resolution. The focused 1/e2 beam diameter of waveform-controlled pulses has a constant value without depending on the intensity of the laser pulses. Only the mean-power density is proportional to the power of the laser pulses. The beam-intensity distribution of a short pulse length of 0.3 ms width can be also measured precisely. Suitable welding conditions for mild steel and some aluminum alloys can be determined by the mean power density and the pulse length of a square pulse.