Using the characteristic of refractive index are smaller than 1 in the reststrahlen band,we can produce photonic crystal having forbidden band in the middle infrared and far infrared.

由此可知利用材料在剩余射线带内折射率小于1特性，我们可以制备出中红外区和远红外区存在带光子晶体。

Incorporating array of metallic wires into the host media, such as ferrimagnet YIG under an external magnetic bias field, is a novel method to synthesize negative refractive index (NRI) material.

摘要以亚铁磁煤-YIG为基体，在其中嵌入金属导体线阵列是人工合成负折射率微波媒种新方法。