Study On Preparation And Laser Damage Morphologies Character Of YAG Single Crystal And Ceramics And Their Machansims

YAG crystal was prepared by traditional Czochrolski Method and YAG transparent ceramics was prepared by solid-state reaction method, and the performances of YAG crystal and ceramics were characterized. In order to investigate laser-induced damage of YAG material, millisecond, nanosecond and femtosecond pulsewidth laser were used to induce damage of YAG, three kinds of damage mechanism for YAG by laser were analyzed.For preparation of YAG crystal, the experimental results show that: YAG crystal was prepared by Czochrolski Method-a kind of traditional crystal methods, which guarantee the quality of YAG crystal. To compare the characterization of YAG crystal specimen by heat treatment under vacuum or air with as prepared, XPS, transimittance, FWHM of XRD were used, trying to determine the effect factors of optical quality for YAG crystal.For preparation of YAG transparent ceramic, study results show that:YAG powder could be synthesized by high-purity Y₂O₃, Al₂O₃ powder or Y₂O₃,Al powder by solid-state reaction method. The temperature of YAG powder synthesized by latter method is lower than former one, and YAG powder could be synthesized at 1200℃, YAG transparent ceramics could be prepared by Y₂O₃ ,Al₂O₃ powder and could not by Y₂O₃, Al powder.In this paper, ms laser was used to induce damage for YAG crystal, and the single pulse ms laser induced damage and its mechanism was studied in detail. The results show that: the main mechanism of ms laser damage for YAG crystals or transparent ceramic is melting, cone-shaped keyhole is formed on the surface, and its depth is near linear to laser energy. Laser induced damage to YAG based on heat conduction, melting, vaporization, ionization four processes, a mathematical model is established and results agree well with experimental data. At the same time cutting kerf of YAG crystal by ms laser is analyzed and explained by theory.YAG crystal and transparent ceramics damaged morphology and mechanism by laser is of a detailed study. Research result shows that: For surface damaged YAG by ns laser, surface evaporation and bulk evaporation are the main damage mechanism; For bulk damaged YAG by ns laser, thermal explosion is the main damaged mechanism, crystal is melt by laser inside, then expanded, surface uplift, crystal will be crack while the laser pulse energy sufficiently large; The damage mechanism of YAG ceramic is similar to that of YAG crystal.Ultrashort pulse fs laser induced damage morphology and its mechanism is also studied in detail. Result shows that: main mechanism of crystal damage by laser is strong electric field strip the surface atom. Ablation threshold of different treatment of YAG is determined by maximum value method and it is very near to the value computed by dielectric abalation threshold by Robert Eason, the result is similar between Betis'critical electric field threshold with Bulgakova'Coulomb explosion theory, Strong electric field stripping the atom on the surface is analyzed from theory, Y atom, Al atom, Atom emission spectra of Y ion, Al ion, YO molecule, AlO molecule appear for YAG by fs laser induced damage.