基于MEMS技术的太赫兹超材料三维电磁感应透明慢光调控器

The ever increasing need for faster data rates is pushing the wireless communication systems to sub-terahertz spectral range. The cutting edge high speed electronic devices based on high electron mobility transistors barely meet the speed requirements of these applications and seriously challenge the further scaling of communication channels to higher operational frequencies. In the past decade, artificially engineered materials popularly known as “metamaterials” have been proposed and explored as an efficient means of manipulating terahertz (THz) waves. Slow light devices form an integral part of any wireless communication system as they enable the realization of optical delay lines, buffers, modulators, etc. Near-field coupling in planar metamaterials provides an access route for the realization of optical analogue of electromagnetically inducted transparency (EIT) which is basically a quantum phenomenon that enables enhanced slow light characteristics and high non-linear properties. Active control of EIT is critical for the realization of functional slow light and non-linear THz devices. Currently reported approaches based on optical and thermal means, demands for bulky setups or exotic materials or provide low response time and so are not ideal for the miniaturized or commercial systems. Microelectromechnical system (MEMS) integrated into the near-field coupled resonators will enable physical control of the resonator geometry and their coupling distance and will enable highly efficient and miniaturized solution. In this proposal, 3D reconfigurable of MEMS metamaterials for coupled mode systems will be systematically designed. The in-plane 2D metamaterials under comb-drive actuation will be integrated with out-of-plane reconfigurable stress beam microcantilevers to make 3D reconfigurable metamaterial. The coupling and tuning mechanism of EIT slow light in this device are profoundly studied and revealed in terms of the influence of geometrical variation of unit cell on light-matter interaction. The scalable nature of MEMS and metamaterial will make this technology disruptive over the wide range of microwave, THz and infrared spectral applications in the near future.

慢光器件作为无线通信系统中的重要组成部分，能够提供太赫兹波的缓冲、调控和延迟功能。而超材料平面内的近场电磁耦合可以激发太赫兹的电磁感应透明效应(EIT)，这是一种强烈非线性的慢光表现。目前基于光学式和热学式调控EIT，由于特殊材料的引入、较大的器件体积和较慢的响应速度阻碍了微型系统和商业化集成。本项目创新地提出基于微机电系统 (MEMS) 的太赫兹超材料三维调控器，采用集成静电梳齿驱动和悬臂梁结构驱动实现平面内和平面外调控EIT；研究太赫兹波与超材料的EIT慢光电磁场耦合作用物理机制，探索通过改变超材料结构单元的相对位置而产生太赫兹EIT慢光频谱共振响应变化的调控机理。此项目可以为未来的高性能太赫兹超材料调控器的设计和制成提供完善的研究和实验平台。

慢光器件作为无线通信系统中的重要组成部分，能够提供太赫兹波的缓冲、调控和延迟功能。而超材料平面内的近场电磁耦合可以激发太赫兹的电磁感应透明效应(EIT)，这是一种强烈非线性的慢光表现。本项目设计了一组共四个基于两个同轴的双开口环谐振器的太赫兹超材料器件，可以实现在太赫兹波段的双频带调谐。同时，对入射电磁波进行了入射角、极化角的研究，结果表明，该器件可以实现幅值的调制，并且有对极化角不敏感的特性，有望用作可应用在任意形状表面的传感器。同时制备了一种基于弯曲传感的 “Ω”结构的超薄太赫兹超材料器件。器件的衬底为柔性材料parylene-C，上面是一层金属，单元结构为镂空的环。由于两种材料热膨胀系数的不同导致残余应力的存在，器件在制备完成后，中间的圆盘向上翘起约4.2°。将器件由外向内挤压，当挤压方向与Ω的对称轴垂直，圆盘的翘起角度几乎没有变化，反之，弯曲应力与翘起角度呈正相关。将4个基础结构单元依次旋转90°形成旋转对称的结构，弯曲实验表明，仅仅1.3 × 10−4的应力变化，就可以产生高达31.1%的幅度调制，因此该器件可以用作超灵敏传感器。