Tunable asymmetric transmission across stretchable chiral metamaterial

Abstract

A stretchable chiral metamaterial with L-shaped and T-shaped Au patterns (SCMM-LT) is proposed to generate asymmetric transmission (AT) for circularly polarized waves on the polydimethylsiloxane substrate in the mid-infrared region. The peak value of AT can reach 50.02% at the resonance wavelength of 19.1 µm, owing to the enantiomerically sensitive plasmons. With stretching along the x axis and the y axis. respectively, the band of AT shifts to a longer wavelength, which proves the SCMM-LT can be a candidate as the tunable chiral metamaterial. In the future, the proposed stretchable chiral metamaterial could potentially possess high applicability for wearable electronic devices in a variety of sensor fields.

Active tuning hBN phonon polaritons and spontaneous emission rates based on VO₂ and graphene

“…双曲线材料(HMs)因具有各向异性而在纳米光子领域引起了极大的兴趣 [1][2][3] ． hBN 作为一种天然的 HMs， 因在中红外光谱范围内支持声子极化激元 (PhPs)， 已经在自发发射 (SE) 增强、 近场辐射传热和折射率传感 [4][5][6][7] 等领域得到了应用． 然 而，由于固有晶格导致的低效可调谐性，hBN PhPs 的可调谐性仍然是一个值得 研究的课题 [8] ． 过去的研究表明将不同功能材料堆叠组合成异质结构，为通过耦合作用调谐 材料特性并揭示其潜在物理机制提供了灵活方法 [9] ．由于石墨烯在红外和太赫兹 光谱范围内支持可调谐的表面等离子体极化激元(SPPs)，且石墨烯可以灵活地 与其他 HMs 或微纳结构结合，为实现光电器件的可调谐性提供了可能 [10,11] ，石 墨烯已经被用于实现可调谐的 PhPs 色散模式、近场辐射传热和光谱吸收．除石 墨烯外，包括二氧化钒(VO 2 )和 Ge 2 Sb 2 Te 5 在内的相变材料因具有的独特光学 特性，在加热或脉冲激光刺激时会发生从绝缘态到金属态的相变，其在实现主动 可调谐的光-物质相互作用方面取得了丰硕的成果 [4,9,[12][13][14] ．相比于 Ge 2 Sb 2 Te 5 可 以在 438 K 发生相变，VO 2 的相变温度仅为 340 K，因此 VO 2 在发生相变过程中 对其它复合材料的影响相对较小 [12,15,16] ． 此外， VO 2 的相变温度可通过掺杂 W、 Ti、Mg 或 Al 等金属纳米颗粒(M x V 1-x O 2 )进行调节 [15,17] ，例如通过将 W x V 1-x O 2 中的 x 设置为 1.5%， 就可以将 VO 2 从绝缘态 VO 2 (I)到金属态 VO 2 (M)的相变温度 降低至 295 K [18] ． 基于 VO 2 的低相变温度以及可通过掺杂金属纳米粒子调节相变 温度的优势，VO 2 已经在温度自适应辐射涂层、能量存储和可重构电子设备中得 到广泛应用 [19][20][21] 折射系数 n 和消光系数 k 如图 1(b) [15] ，为保证 VO 2 作为基底时无透射，应使 得 VO 2 的厚度大于 5 μm，在本文中取值为 10 μm．hBN…”

Switchable asymmetric transmission with broadband polarization conversion in vanadium dioxide-assisted terahertz metamaterials

“…Since Menzel et al first proposed the AT effect of linearly and circularly polarized waves, 9 various MMs have been proposed to obtain the AT effect across the frequency range from visible light to microwave bands. [10][11][12][13] Associated with AT, polarization conversion, 14 which is used to describe changes in the polarization direction of electromagnetic waves, is also efficiently achieved by different schemes, such as Z-shaped, 15 diagonal-shaped, 16 periodic pillar array, 17 etc. However, most of the above-mentioned MMs are prepared from traditional noble metals, whose characterization makes the function of MMs fixed after fabrication, which limits the development of tunable multi-functional MMs.…”

High-efficiency modulation of broadband polarization conversion with a reconfigurable chiral metasurface

“…41 The AT effect and polarization conversion of electromagnetic waves on the metasurface structures have been studied in the range of microwaves, [42][43][44][45][46][47] terahertzs [48][49][50][51] and optical band. [52][53][54][55][56] The design of these structures can be used for polarizers and have practical applications in imaging, communication and sensing. 7 Although these designed metasurface structures can achieve high efficiency and broadband AT effects, once these metasurface structures are designed, their function and performance are xed and lack effective tunability, which limits their practical applications.…”