Laboratory for Future Interdisciplinary Research of Science and Technology, Department of Electrical and Electronic Engineering, Tokyo Institute of Technology 2-12-1, Ookayama, Meguro-ku, Tokyo, 152-8552, Japan.
Department of Orthopaedic Surgery, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, 113-8519, Japan.
Sci Rep. 2019 Mar 5;9(1):3498. doi: 10.1038/s41598-019-39015-6.
Plasmon-based devices are powerful for use in highly sensitive evanescent-field detection and analysis, but they exhibit the problem of limited frequency tunability for fixed structures. This feature causes problems in the multi-frequency investigations required for materials characterization, bio-related research, etc. Here, we propose and fabricate a spiral-shaped plasmonic structure that enables a continuous frequency-tuneable evanescent-field concentration in the terahertz (THz) region with simple operation. The device also increases the electric field intensity at the subwavelength aperture, thus significantly amplifying the transmission. Highly tuneable transmission bands are observed by simply rotating the spiral plasmonic structure, which are in good agreement with the behaviour expected from electromagnetic simulation. Medical examinations are performed by measuring the interactions between the frequency-tuneable plasmons and bio-samples, which enables observing distinct tissue-dependent transmission spectra and images. The developed device simultaneously offers the advantages of both plasmonic devices and frequency-tuneable devices, which can increase the availability and versatility of evanescent-field THz sensing and analysis. The mechanism presented will shed light on THz plasmonics and motivate the implementation of a variety of applications based on plasmon-mediated THz technologies.
基于等离子体的器件在高灵敏度消逝场检测和分析中非常强大，但它们存在固定结构频率可调性有限的问题。这一特性在材料特性、生物相关研究等所需的多频率研究中造成了问题。在这里，我们提出并制造了一种螺旋形等离子体结构，能够在太赫兹（THz）区域实现连续可调谐的消逝场集中，操作简单。该器件还增加了亚波长孔径处的电场强度，从而显著放大了传输。通过简单地旋转螺旋等离子体结构，可以观察到高度可调谐的传输带，这与电磁模拟所预期的行为非常吻合。通过测量可调谐等离子体与生物样本之间的相互作用来进行医学检查，这使得可以观察到明显的组织相关传输光谱和图像。所开发的器件同时具有等离子体器件和可调谐器件的优点，这可以增加消逝场太赫兹传感和分析的可用性和通用性。所提出的机制将为太赫兹等离子体学提供启示，并激发基于等离子体介导的太赫兹技术的各种应用的实现。
