1] Laboratory of Applied Research on Electromagnetics (ARE), Zhejiang University, Hangzhou 310027, China [2] Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona 85721, USA.
Department of Electrical and Computer Engineering, University of Arizona, Tucson, Arizona 85721, USA.
Nat Commun. 2014 Dec 19;5:5841. doi: 10.1038/ncomms6841.
Artificial effective media are attractive because of the fantastic applications they may enable, such as super lensing and electromagnetic invisibility. However, the inevitable loss due to their strongly dispersive nature is one of the fundamental challenges preventing such applications from becoming a reality. In this study, we demonstrate an effective gain medium based on negative resistance, to overcompensate the loss of a conventional passive metamaterial, meanwhile keeping its original negative-index property. Energy conservation-based theory, full-wave simulation and experimental measurement show that a fabricated sample consisting of conventional sub-wavelength building blocks with embedded microwave tunnel diodes exhibits a band-limited Lorentzian dispersion simultaneously with a negative refractive index and a net gain. Our work provides experimental evidence to the assertion that a stable net gain in negative-index gain medium is achievable, proposing a potential solution for the critical challenge current metamateiral technology faces in practical applications.
人工等效媒质具有诱人的应用前景，例如超透镜和电磁隐形。然而，由于其强烈的色散性质而导致的不可避免的损耗，是阻止这些应用成为现实的一个基本挑战。在这项研究中，我们展示了一种基于负电阻的等效增益媒质，可以补偿传统无源超材料的损耗，同时保持其原始的负折射率特性。基于能量守恒的理论、全波模拟和实验测量表明，由嵌入微波隧道二极管的传统亚波长结构组成的一个样品，同时表现出有限带宽的洛伦兹色散、负折射率和净增益。我们的工作为这样一种断言提供了实验证据，即在负折射率增益媒质中实现稳定的净增益是可行的，为当前超材料技术在实际应用中面临的关键挑战提出了一种潜在的解决方案。
