Quantum and Thermal Interaction between Substances and Combined Laser Beams with Different Wavelength

1)激光波长对烧蚀加工特性的影响烧蚀打孔是一种材料。激光波长为调Q激光的二倍频(λ=5 32 nm)、三倍频(λ=35 5 nm)和四倍频(λ=2 6 6 nm)。在二次、三次高次谐波打孔过程中，即使在非扇形脉冲作用下，孔周围仍会出现热影响区，多次激光照射后会产生裂纹。但是，由于受到四次高次谐波的影响，热影响区几乎看不到，整个过程变成了量子模。此外，还研究了等离子体的发光行为，发现入射光束与等离子体之间的相互作用对烧蚀过程有显著的影响。2)不同波长的组合激光对各种金属熔化特性的影响组合LAS…用不同波长的Er激光，即基频激光(L=1064 nm)和调Q激光倍频(L=532 nm)照射到不同的金属表面。结果表明，峰值功率为5kW的基波激光不能熔化纯铜、铝等高反射金属。而加入小功率倍频激光(40W)后，熔化效率提高了130%。在其他金属中也证实了类似的影响。在厚度小于0.1 mm的超薄薄板搭接焊接中，基本波长的YAG激光器不能焊接，但在组合激光的情况下焊接成功。3)激光焊接小孔动力学的直接观察利用高时间分辨率的X射线透射式成像系统观测了连续和脉冲激光焊接小孔的行为。在连续激光焊接中，小孔的起伏很快，这种不稳定导致了气孔的形成。而在脉冲激光点焊中，当激光功率迅速停止时，小孔迅速坍塌，金属蒸汽和保护气体被限制在小孔内，导致小孔形成大气孔。抑制孔洞形成最有效的方法是使用受控脉冲波。较少

The outline of results obtained in the research period from 1998 to 2001are summarized below.1) Effect of wavelength of laser on ablation processing characteristicsAblation hole drilling pheaoniena were materials. Laser wavelength used were the second high harmonic (λ=532 nm), third high harmonic (λ=355 nm) and fourth high harmonic (λ=266 nm) of Q-switched YAG laser. In the hole drilling of acrylic plate by the second and third high hamonics, there appeared heat affected zone around the hole in spite of nono-secorid pulse and cracking was generated after multiple laser irradiation. However, by the fourth high harmonics, the heat affected zone was hardly seen and the process became the quantum mode. Also, light emission behavior from plasma was studied and it was revealed that the interaction between incident beam and plasma gave significant effect of ablation process.2) Effect of combined laser beams with different wavelength on melting characteristics of various metalsThe combined las … More er beams with different wavelength, i.e., basic wavelength of YAG laser (l=1064 nm) and second high harmonics (SHG) of Q-switched YAG laser (l=532 nm) was irradiated on the various metals. It was revealed that the high reflective metals such as pure copper and aluminum could not melt by basic wave of YAG laser with peak power of 5 kW. However, the addition of small power SHG YAG laser (40 W) enhanced the melting efficiency greatly up to 130 percent. The similar effect was confirmed in other metals. In the lap welding of very thin sheet less than 0.1 mm in thickness, the basic wavelength YAG laser can not weld, but it was successfully welded when the combined laser beams were used.3) Direct observation of keyhole dynamics in laser weldingKeyhole behaviors in CW and pulsed laser welding were observed by X-ray transmission imaging system with high temporal resolution. In CW laser welding, the keyhole fluctuated quickly and this instability caused the porosity formation. While, in pulsed laser spot welding, a keyhole was quickly collapsed and metal vapor as well as shielding gas were confined in the keyhole when laser power was quickly terminated which led the formation of large porosity. The most effective way to suppress the porosity formation was the use of controlled pulse wave. Less