The layer of air near the earth is cooler than an overlying layer. 靠近地表的空气层比其上面的层气温低。
If the thickness of one air layer is changed, a defect comes into being, and the corresponding defect mode in the PBG will change accordingly. 如果改变某空气层的厚度,会在光带隙中产生缺陷态,缺陷态的位置随该空气层的厚度的改变而改变。