For high-permeability grain-oriented Si steels, it has been proved that the core loss is remarkably reduced by domain refinement. In this study, the magnetic domain structure has been refined by using an Nd:YAG laser under various operation conditions. We have, in particular, investigated the relation between the efficiency of laser scribing and the optical wavelength of the laser pulse. By using the second or third harmonic generation (SHG or THG) method, the fundamental wavelength (1064 nm) of the scribing laser was changed to 532 mn or 355 nm. The core loss has been improved by as much as 19% for the THG laser pulses.

Keywords: laser scribing; wavelength dependence; core loss; second harmonic generation; third harmonic generation