Wavelength optimization for machining metals with the harmonic generations of a short pulsed Nd:YAG laser

The wavelength conversion for a short pulsed Nd:YAG laser has been implemented from infrared to visible and to ultraviolet spectra by using nonlinear optical crystals. The analytical method of wavelength optimization for machining metals with various harmonic generations of a Nd:YAG laser is presented in this paper. Combining the absorptivity of metal and the conversion efficiency of laser apparatus, the absorption efficiency is proposed to select an optimum machining wavelength. Various metals have different optimum machining wavelengths. The optimum machining wavelengths for gold, silver, and copper are in the third-, fourth- and second-harmonic generations of a Nd:YAG laser, respectively. For other metals, such as nickel, their optimum machining wavelengths are all in the fundamental wavelength of a Nd:YAG laser.