Li Peining, Lewin Martin, Kretinin Andrey V, Caldwell Joshua D, Novoselov Kostya S, Taniguchi Takashi, Watanabe Kenji, Gaussmann Fabian, Taubner Thomas
Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany.
1] Institute of Physics (IA), RWTH Aachen University, Aachen 52056, Germany [2] Fraunhofer Institute for Laser Technology ILT, Aachen 52074, Germany.
Nat Commun. 2015 Jun 26;6:7507. doi: 10.1038/ncomms8507.
Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications.
双曲线材料呈现出亚衍射、高定向性、体积受限的极化激元模式。在此我们报告，双曲线声子极化激元使得六方氮化硼平板能够实现令人兴奋的近场光学应用，包括异常成像现象（如被研究物体的放大重构）和亚衍射聚焦。放大成像和超分辨率聚焦均基于双曲线声子极化激元的体积受限、与波长相关的传播角来解释。借助先进的红外纳米成像技术和最先进的中红外激光源，我们成功地在I型和II型双曲线条件下演示并可视化了这些意外现象，二者均自然发生于六方氮化硼中。这些工作为理解双曲线声子极化激元在近场光学成像、引导和聚焦应用中的作用提供了完整且直观的物理图景。
