What makes single-helical metamaterials generate "pure" circularly polarized light?
What makes single-helical metamaterials generate "pure" circularly polarized light?
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DOI：
10.1364/oe.20.001552
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发表时间：
2012-01
期刊：
影响因子：
3.8
通讯作者：
Lin Wu;Zhenyu Yang;Ming Zhao;Peng Zhang;Zeqin Lu;Yang Yu;Shengxi Li;Xiuhua Yuan
中科院分区：
文献类型：
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作者：
Lin Wu;Zhenyu Yang;Ming Zhao;Peng Zhang;Zeqin Lu;Yang Yu;Shengxi Li;Xiuhua Yuan
具有左手螺旋超材料的圆偏振器可以传输右手圆偏振（RCP）光而几乎没有损耗。但是在透射光中会产生一定量的左旋圆偏振光，这就是圆偏振器的噪声。因此，我们将RCP光强度与LCP光强度的比值定义为信噪比（S/N）。在我们以前的工作中，发现多螺旋超材料圆偏振器的信噪比比单螺旋超材料圆偏振器的信噪比高两个数量级。然而，如何制作微米或亚微米尺寸的多螺旋结构一直是一个巨大的挑战。单螺旋超材料是否有可能获得与多螺旋超材料同样高的信噪比？为了回答这个问题，我们采用时域有限差分法（FDTD）系统地研究了单螺旋异向介质的结构参数对信噪比的影响。结果表明，单螺旋超材料的信噪比也可达到30 dB左右，与多螺旋超材料的信噪比相当。此外，我们用天线理论解释了这一现象，并对单螺旋圆极化器的性能进行了优化。
Circular polarizers with left-handed helical metamaterials can transmit right-handed circularly polarized (RCP) light with few losses. But a certain amount of left-handed circularly polarized (LCP) light will occur in the transmitted light, which is the noise of the circular polarizer. Therefore, we defined the ratio of the RCP light intensity to the LCP light intensity as the signal-to-noise (S/N) ratio. In our previous work, it's found that circular polarizers with multi-helical metamaterials have two orders higher S/N ratios than that of single-helical metamaterials. However, it has been a great challenge to fabricate such multi-helical structures with micron or sub-micron feature sizes. Is it possible for the single-helical metamaterials to obtain equally high S/N ratios as the multi-helical ones? To answer this question, we systematically investigated the influences of structure parameters of single-helical metamaterials on the S/N ratios using the finite-different time-domain (FDTD) method. It was found that the single-helical metamaterials can also reach about 30dB S/N ratios, which are equal to the multi-helical ones. Furthermore, we explained the phenomenon by the antenna theory and optimized the performances of the single-helical circular polarizers.