亚波长环形电磁结构的光学特性研究

Study on Optical Properties of Subwavelength Electromagnetic Materials

利用聚焦离子束(focusedion beam,FIB)刻蚀方法在120nm厚的金膜上制备了实验测量样品。再用实验的方法测量了在可见光波段及近红外波段的透射曲线,当样品具有相同的晶格常数以及空气孔直径时,环形空气孔结构,不仅具有六重旋转对称性还具有中心对称性,它的最大透射率大约是正方角晶格空气孔的5倍。亚波长环形空气孔结构透射增强峰的在可见光波段,而正方晶格空气孔的透射增强峰在近红外波段,样品的透射强度和透射增强峰的位置各不相同,证明了结构的旋转对称性对透射曲线的影响。

By mean of focused ion beam（FIB） etching,the samples were prepared on a 120 nm-thick gold film.The comparison of optical transmission shows that the circular hole arrays,which possesses the six-fold rotational symmetry and central symmetry,has higher transmittance than the two periodic structures＇.Its peak efficiency is about five times larger than that of the square hole arrays.It can be attributed to the stronger constructive interference of multiple scattered waves in a higher symmetrical hole structure.The position of the enhanced peak for the circular hole arrays locates in the visible region,while that of square hole arrays is in the infrared region.