In-plane anisotropy in biaxial ReS2 crystals probed by nano-optical imaging of waveguide modes
Fabian Mooshammer, Sanghoon Chae, Shuai Zhang, Yinming Shao, Siyuan Qiu, Anjaly Rajendran, Aaron J. Sternbach, Daniel J. Rizzo, Xiaoyang Zhu, P. James Schuck, J… 展开作者
Fabian Mooshammer, Sanghoon Chae, Shuai Zhang, Yinming Shao, Siyuan Qiu, Anjaly Rajendran, Aaron J. Sternbach, Daniel J. Rizzo, Xiaoyang Zhu, P. James Schuck, James C. Hone, D. N. Basov
Near-field imaging has emerged as a reliable probe of the dielectric function of van der Waals crystals. In principle, analyzing the propagation patterns of subwavelength waveguide modes (WMs) allows for extraction of the full dielectric tensor. Yet previous studies have mostly been restricted to high-symmetry materials or narrowband probing. Here, we resolve in-plane anisotropic WMs in thin rhenium disulfide (ReS2) crystals across a wide range of near-infrared frequencies. By tracing the evolution of these modes as a function of crystallographic direction, polarization of the electric field and sample thickness, we have determined the anisotropic dielectric tensor including the elusive out-of-plane response. The excitonic absorption at ~1.5 eV manifests itself as a clear backbending feature in the WM dispersion and a reduction of the quality factors as fully supported by numerical calculations. Our results extend the sensitivity of near-field microscopy towards biaxial anisotropy and provide key insights into the optoelectronic properties of ReS2.
Effective Dielectric Constants of Photonic Crystal of Aligned Anisotropic Cylinders: Application to the Optical Response of Periodic Array of Carbon Nanotubes
Controlling and focusing of in-plane hyperbolic phonon polaritons in α-MoO3 with plasmonic antenna
范德华材料中的双曲声子极化激元（HPhPs）具有将长波电磁场限制到深亚波长尺度的能力。与单轴vdW双曲材料如六方氮化硼（h-BN）形成鲜明对比的是，最近出现的双轴双曲材料如α-MoO 3和α-V2 O 5由于其独特的面内双曲色散，进一步在平坦区控制光方面带来了新的自由度。然而，这种平面内HPhPs的控制和聚焦迄今为止仍然是难以捉摸的。在这里，我们提出了一个通用的技术发射，控制和聚焦的平面HPhPs在α-MoO 3与几何设计的等离子体天线。利用高分辨率近场光学成像技术，我们直接激发并映射了真实空间中的HPhPs波前。我们发现亚波长操纵和聚焦行为强烈依赖于天线末端的曲率。该策略在宽带光谱区域中有效地操作。这些发现不仅可以为双轴双曲晶体在纳米尺度上对光的操纵提供基本的见解，而且还为平面纳米光子应用开辟了新的机会。
