Loss-free and active optical negative-index metamaterials
Loss-free and active optical negative-index metamaterials
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DOI：
10.1038/nature09278
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发表时间：
2010-08-05
期刊：
影响因子：
64.8
通讯作者：
Shalaev, Vladimir M.
中科院分区：
文献类型：
--
作者：
Xiao, Shumin;Drachev, Vladimir P.;Shalaev, Vladimir M.
最近出现的超材料和变换光学领域承诺了一系列令人兴奋的应用，如隐形，具有深亚波长分辨率的光学成像和具有更快信息处理潜力的纳米光子学。在过去的几年里，使用纳米结构金属-电介质复合材料制造光学负折射率超材料（NIMs）的可能性引发了激烈的基础和应用研究（1-10）。然而，所有NIM应用的性能都受到金属固有的强烈能量耗散的限制，特别是在近红外和可见光波长范围内（11，12）。一般来说，损失的数量级太大，为拟议的应用程序，和减少损失的优化设计似乎是遥不可及的。解决这个问题的一种方法是将增益介质纳入NIM设计（13-16）。然而，是否可以实现低损耗的NIM一直是理论争论的主题（17，18）。在这里，我们的实验表明，在超材料的高局部场区域的增益材料的掺入使得有可能制造一个极低的损耗和有源光学NIM。在722和738 nm之间的可见光波长范围内进行损耗补偿，器件的原始损耗限制负折射率和品质因数（FOM）得到了大幅改善。在这个范围内，NIM变得活跃，使得透射和反射中的光强度之和超过入射光束的强度。在737 nm波长处，负折射率从-0.66提高到-1.017，FOM从1增加到26。在738 nm处，预计FOM变得宏观上大，为10（6）的量级。这项研究证明了制造一种光学负折射率超材料的可能性，这种材料不受其金属成分中固有损耗的限制。
The recently emerged fields of metamaterials and transformation optics promise a family of exciting applications such as invisibility, optical imaging with deeply subwavelength resolution and nanophotonics with the potential for much faster information processing. The possibility of creating optical negative-index metamaterials (NIMs) using nanostructured metal-dielectric composites has triggered intense basic and applied research over the past several years(1-10). However, the performance of all NIM applications is significantly limited by the inherent and strong energy dissipation in metals, especially in the near-infrared and visible wavelength ranges(11,12). Generally the losses are orders of magnitude too large for the proposed applications, and the reduction of losses with optimized designs seems to be out of reach. One way of addressing this issue is to incorporate gain media into NIM designs(13-16). However, whether NIMs with low loss can be achieved has been the subject of theoretical debate(17,18). Here we experimentally demonstrate that the incorporation of gain material in the high-local-field areas of a metamaterial makes it possible to fabricate an extremely low-loss and active optical NIM. The original loss-limited negative refractive index and the figure of merit (FOM) of the device have been drastically improved with loss compensation in the visible wavelength range between 722 and 738 nm. In this range, the NIM becomes active such that the sum of the light intensities in transmission and reflection exceeds the intensity of the incident beam. At a wavelength of 737 nm, the negative refractive index improves from -0.66 to -1.017 and the FOM increases from 1 to 26. At 738 nm, the FOM is expected to become macroscopically large, of the order of 10(6). This study demonstrates the possibility of fabricating an optical negative-index metamaterial that is not limited by the inherent loss in its metal constituent.