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固体开始导光的波长与其禁带间距的能量相符合。其长波截止波长通常决定于固体的品格或组成元素的品格型的吸收。这二个波长极限,可从其组成元素在周期表中的位置,也就是其原子量及电子结构而定性的给予判断。在透射范围内的吸收通常与试样中的杂质或缺陷有关,因而又与试样制作方法有关。为便于比较,目前所使用的材料可归纳为四大类:碱金属及碱土金属卤化物,结晶半导体,热压Ⅱ—Ⅵ族化合物及硫化物玻璃。它们之间的区别某种程度上在于制造方法及化学成分。比较对于光学上的应用是很重要的。某些物理性能表明:每一族或每一属的材料都有它自身的缺点。现有材料质量上的改进,目前主要在于制造方法。例如结晶半导体通常是以单晶形式使用了,但是以这种高质量的材料制造光学元件,其尺寸是被限制了。近来,材料科学家已经知道高性能的光学元件能由高纯的,其晶粒大小可以控制的多晶材料来制造。为此,目前的研究计划的目标是制作大块多晶体材料的新工艺。新的熔炼方法和化学蒸气沉积法已经发展成熟。强调质量必然要求发展新的检验技术。这些新的检验技术必须提供定量的与材料质量有关的知识,为制造材料服务。
The wavelength at which the solid begins to light is consistent with the energy of its forbidden band spacing. The long-wavelength cut-off wavelength is usually determined by the absorption of the solid or the character of the constituent elements. These two wavelength limits can be judged qualitatively from the position of their constituent elements in the periodic table, that is, their atomic weight and electronic structure. The absorption in the transmission range is usually related to the impurities or defects in the sample and therefore to the sample preparation method. The materials currently used can be grouped into four broad categories for comparison: alkali metal and alkaline earth halides, crystalline semiconductors, hot pressed II-VI compounds and sulfide glasses. The difference between them is to some extent the method of manufacture and the chemical composition. Comparison is very important for optical applications. Some physical properties show that the material of each family or genus has its own drawbacks. Improvements in the quality of existing materials are mainly based on manufacturing methods. Crystalline semiconductors, for example, are usually used in the form of single crystals, but optical elements are manufactured with such high-quality materials and their size is limited. Recently, material scientists have come to realize that high-performance optical components can be made from highly pure polycrystalline materials whose grain size can be controlled. For this reason, the current research project aims to create new processes for bulk polycrystalline materials. New smelting methods and chemical vapor deposition methods have matured. Stressing that quality necessarily requires the development of new inspection techniques. These new inspection techniques must provide a quantitative knowledge of material quality to service the material.