Yu Shang-Jie, Yao Helen, Hu Guangwei, Jiang Yue, Zheng Xiaolin, Fan Shanhui, Heinz Tony F, Fan Jonathan A
Department of Electrical Engineering, Stanford University, Stanford, California 94305, United States.
Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
ACS Nano. 2023 Nov 28;17(22):23057-23064. doi: 10.1021/acsnano.3c08735. Epub 2023 Nov 10.
Low-dimensional, strongly anisotropic nanomaterials can support hyperbolic phonon polaritons, which feature strong light-matter interactions that can enhance their capabilities in sensing and metrology tasks. In this work, we report hyperbolic polaritonic rulers, based on microscale α-phase molybdenum trioxide (α-MoO) waveguides and resonators suspended over an ultraflat gold substrate, which exhibit near-field polaritonic characteristics that are exceptionally sensitive to device geometry. Using scanning near-field optical microscopy, we show that these systems support strongly confined image polariton modes that exhibit ideal antisymmetric gap polariton dispersion, which is highly sensitive to air gap dimensions and can be described and predicted using a simple analytic model. Dielectric constants used for modeling are accurately extracted using near-field optical measurements of α-MoO waveguides in contact with the gold substrate. We also find that for nanoscale resonators supporting in-plane Fabry-Perot modes, the mode order strongly depends on the air gap dimension in a manner that enables a simple readout of the gap dimension with nanometer precision.
低维、强各向异性的纳米材料能够支持双曲线声子极化激元，其具有强光与物质相互作用的特性，可增强它们在传感和计量任务中的能力。在这项工作中，我们报道了基于微尺度α相三氧化钼（α-MoO）波导和悬浮在超平金衬底上的谐振器的双曲线极化激元标尺，其展现出对器件几何形状异常敏感的近场极化激元特性。利用扫描近场光学显微镜，我们表明这些系统支持强受限的图像极化激元模式，该模式呈现出理想的反对称间隙极化激元色散，对气隙尺寸高度敏感，并且可以使用一个简单的解析模型进行描述和预测。用于建模的介电常数通过与金衬底接触的α-MoO波导的近场光学测量精确提取。我们还发现，对于支持面内法布里-珀罗模式的纳米尺度谐振器，模式阶数强烈依赖于气隙尺寸，其方式能够以纳米精度简单读出气隙尺寸。
