Qin Tianwei, Ma Weiliang, Wang Tao, Li Peining
Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074, China.
Optics Valley Laboratory, Hubei, 430074, China.
Nanoscale. 2023 Jul 20;15(28):12000-12007. doi: 10.1039/d3nr02213g.
Phonon polaritons in polar crystals have recently gained significant attention due to their remarkable confinement and enhancement of electromagnetic fields, low group velocities, and low losses. However, these unique properties, resulting from the coupling between photons and lattice vibrations, exhibit limited spectral responses that may hinder their practical applications. Here, we propose and experimentally demonstrate that polar van der Waals heterostructures can integrate their polar constituents to enable broadband phonon polariton responses. A polar heterostructure is created by simply transferring thin flakes of two polar van der Waals materials, hexagonal boron nitride (hBN) and α-phase molybdenum trioxide (α-MoO), onto a polar quartz substrate. Direct infrared nanoimaging experiments show that this integrated heterostructure supports phonon polaritons in a broadband infrared spectral range from 800 to 1700 cm. Further, numerical calculations predict vibrational strong coupling for a few molecule monolayers with multiple molecular absorption modes and phonon polaritons in the heterostructure. Our findings suggest that broadband phonon polariton responses in van der Waals integrated heterostructures have the potential to pave the way for the development of broadband and integrated infrared devices of molecular sensing, signal processing, and energy control.
由于其显著的电磁场限制和增强、低群速度以及低损耗，极性晶体中的声子极化激元最近受到了广泛关注。然而，这些由光子与晶格振动之间的耦合产生的独特性质，表现出有限的光谱响应，这可能会阻碍它们的实际应用。在这里，我们提出并通过实验证明，极性范德华异质结构可以整合其极性成分，以实现宽带声子极化激元响应。通过简单地将两种极性范德华材料——六方氮化硼（hBN）和α相三氧化钼（α-MoO）的薄片转移到极性石英衬底上，就可以创建一个极性异质结构。直接红外纳米成像实验表明，这种集成异质结构在800至1700 cm的宽带红外光谱范围内支持声子极化激元。此外，数值计算预测了具有多个分子吸收模式的少数分子单层与异质结构中的声子极化激元之间的振动强耦合。我们的研究结果表明，范德华集成异质结构中的宽带声子极化激元响应有可能为分子传感、信号处理和能量控制等宽带和集成红外器件的发展铺平道路。
