Pulsed-laser-induced dark traces in LiNbO(3):Zn and LiNbO(3):Mg

Laser-induced dark traces in LiNbO(3):Zn (7.5 mol.%) and LiNbO(3):Mg (6.5 mol.%) crystals have been studied with the crystals as the component for 1064-532-nm second-harmonic generation of Nd:YAG radiation operating in a pulsed mode. The results show that, at high input power density, both crystals suffer from dark traces, which reduce the second-harmonic-generation efficiency. The dark traces are induced by the 532-nm radiation and can be recovered after the laser beam is shut off. The transmission loss spectra show a broad absorption peak near 400 nm.