Wu Yingjie, Ou Qingdong, Dong Shaohua, Hu Guangwei, Si Guangyuan, Dai Zhigao, Qiu Cheng-Wei, Fuhrer Michael S, Mokkapati Sudha, Bao Qiaoliang
Department of Materials Science and Engineering, Monash University, Clayton, Victoria, 3800, Australia.
ARC Center of Excellence in Future Low-Energy Electronics Technologies, Monash University, Clayton, Victoria, 3800, Australia.
Adv Mater. 2021 Jul;33(26):e2008070. doi: 10.1002/adma.202008070. Epub 2021 May 17.
Phonon polaritons-light coupled to lattice vibrations-in polar van der Waals crystals offer unprecedented opportunities for controlling light at the nanoscale due to their anisotropic and ultralow-loss propagation. While their analog plasmon polaritons-light coupled to electron oscillations-have long been studied and exhibit interesting reflections at geometrical edges and electronic boundaries, whether phonon polaritons can be reflected by such barriers has been elusive. Here, the effective and tunable reflection of phonon polaritons at embedded interfaces formed in hydrogen-intercalated α-MoO flakes is elaborated upon. Without breaking geometrical continuity, such intercalation interfaces can reflect phonon polaritons with low losses, yielding the distinct phase changes of -0.8π and -0.3π associated with polariton propagation, high efficiency of 50%, and potential electrical tunability. The results point to a new approach to construct on-demand polariton reflectors, phase modulators, and retarders, which may be transplanted into building future polaritonic circuits using van der Waals crystals.
声子极化激元（光与晶格振动的耦合）存在于极性范德瓦尔斯晶体中，由于其各向异性和超低损耗传播特性，为在纳米尺度上控制光提供了前所未有的机会。虽然类比的表面等离激元极化激元（光与电子振荡的耦合）早已得到研究，并且在几何边缘和电子边界处表现出有趣的反射现象，但声子极化激元是否能被此类势垒反射一直不为人知。在此，我们阐述了在氢嵌入的α-MoO薄片中形成的嵌入界面处声子极化激元的有效且可调谐反射。在不破坏几何连续性的情况下，此类嵌入界面能够以低损耗反射声子极化激元，产生与极化激元传播相关的-0.8π和-0.3π的明显相位变化、50%的高效率以及潜在的电学可调性。这些结果指向了一种构建按需极化激元反射器、相位调制器和延迟器的新方法，这可能会被移植到使用范德瓦尔斯晶体构建未来的极化激元电路中。
