Invisibility has been a topic of long-standing interest owing to the advent of metamaterials and transformation optics, but still faces open challenges after its tremendous development in recent decades. One of the big challenges is the narrow bandwidth, as the realization of an invisibility cloak is usually based on a metamaterial—an artificial composite material composed of subwavelength resonator structures that are always associated with dispersion. Different from previous works that have tried to eliminate the material dispersion to enhance the bandwidth of an invisibility cloak, here, it is found that by judiciously harnessing the material dispersion, the bandwidth of the cloak can still be significantly increased. Interestingly, the material dispersion does not violate the law of causality. As a proof of concept, an ultrabroadband terahertz (THz) carpet cloak is experimentally demonstrated through an array of superdispersive microparticles, rendering the target object invisible to detection by both time- and frequency-domain wideband systems. The work presents a feasible invisibility strategy that is closer to practical applications and may pave a brand-new way for the development of dispersion-dominated ultrabroadband metadevices.

中文翻译：

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超色散使能超宽带太赫兹斗篷的实验实现

由于超材料和变换光学的出现，隐形一直是人们长期关注的话题，但在近几十年的巨大发展之后仍然面临着公开的挑战。最大的挑战之一是窄带宽，因为隐形斗篷的实现通常基于超材料——一种由总是与色散相关的亚波长谐振器结构组成的人造复合材料。与以往试图消除材料色散以增强隐形斗篷带宽的工作不同，这里发现，通过明智地利用材料色散，斗篷的带宽仍然可以显着增加。有趣的是，物质色散并不违反因果律。作为概念证明，超宽带太赫兹 (THz) 地毯斗篷通过一系列超色散微粒进行实验证明，使目标物体不可见，无法被时域和频域宽带系统检测到。该工作提出了一种更接近实际应用的可行隐身策略，可能为色散主导的超宽带元器件的发展开辟一条全新的道路。