Development of New Ultra-Precision Machining Using Solid Lasers in Ultraviolet

现代工业对精密零件的需求量很大，因此近年来发展了超精密加工技术。然而，机械加工过程中的加工精度存在三大缺陷，即刀具磨损、变形和热变形。激光烧蚀加工具有非接触、非热加工的特点，是未来超精密加工的重要工艺之一。这种工艺可以解决机械加工中的上述问题，而且这种工艺既可以在样品上沉积材料，也可以在不引入太多热量的情况下从样品中去除材料。该工艺还具有一个特点，即在加工过程中可以用激光干涉仪监测表面形状。主要研究成果如下：1.研制了一套由紫外光激光器、32位计算机、机械扫描装置、激光CVD真空室和测量样品表面形貌的干涉仪组成的超精密激光加工系统。利用YAG激光器和非线性光学晶体进行微细加工，研制出了一种新型的小尺寸固体紫外激光系统。纯金属和熔融二氧化硅可以很容易地被UV激光而不是YAG激光去除，尽管有频率转换的损失。利用六羰基钨的激光烧蚀技术，可以在薄片衬底上以0.1埃/脉冲的速度沉积金属钨薄膜。作为激光CVD成形的一个实例，生成了一个台面。通过将金属激光沉积到衬底上的凹坑中，获得了平坦的表面。与热处理相比，紫外光激光的光化学处理可以在被激光照射的表面获得更光滑的表面。

There is a big demand for getting more precise parts in modern industries, so that the ultra-precision machining has been developed recently. However, there are three drawbacks on the machining accuracy in the mechanical machining process, and the drawbacks are the tool wear, deflection and thermal deformation. The laser machining process using laser ablation is one of the most important process for ultra-precision machining in future because of non-contact and non-thermal machining process. This process can solve the abovementioned problems in mechanical machinings, and also this process can deposit material on a sample as well as remove material from the sample without introducing much heat. This process also has a feature that the surface figure can be monitored by a laser interferometer during the machining process. Research results are summerized as follows :1. There has been developed an ultra-precision laser machining system which consists of UV lasers, a 32-bit computer, a mechanical scanning apparatus, a vacuum chamber for laser CVD, and an interferometer for measuring a surface figure on a sample.2. New solid state UV laser system of a small size has been developed by using a YAG laser and nonlinear optical crystals for micro-fabrication process.3. Pure metals and fused silica canbe easily removed by UV lasers rather than YAG lasers, in spite of having a loss for frequency conversion.4. A metal tungsten film can be deposited on a slicon substrate at a rate of 0.1 angstrom/pulse in thickness by laser ablation of tungsten hexacarbonyl.5. A table mesa has been generated as an example for making shapes by laser CVD. A flat surface has been obtained by laser deposition of metal into a pit on a substrate.6. A much smoother surface can be obtained on a laser-irradiated surface by photo-chemical process of UV lasers by comparison with thermal process of YAG lasers.