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Research on Millimeter-Wave and Submillimeter-Wave Scanning Near-Field Microscopy

毫米波和亚毫米波扫描近场显微镜研究

基本信息

批准号：
13650365
负责人：
NOZOKIDO Tatsuo
金额：
$ 2.24万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

The objective of this research project is to demonstrate the new type of scanning near-field microscopy, i.e. scanning near-field anisotropy microscopy (SNAM) and to quantify images obtained from the scanning near-field microscope system using a metal slit-type probe which we have proposed and developed, in order to visualize physical parameters of objects such as refractive index and refractive index anisotropy, in the millimeter-wave and submillimeter-wave regions. The results obtained in the term of the project follow.In order to quantify images more precisely in the millimeter- and submillimeter-wave regions, we have proposed, designed, and made a new type of sample base to reduce needless signal fluctuations originated from surface modes. We have successfully demonstrated the effectiveness of this new hardware and found that the signal fluctuation reduces to less than 10% of the previous one. This result means that the microscope system we have developed have a potential to give a limiting refractive index sensitivity of better than Δn/n〜0.1. Furthermore, in order to visualize physical parameters of objects, we have proposed an equivalent circuit to describe the interaction between the probe and object, and succeeded to demonstrate the validity of the circuit by computer simulation using a finite element method and by experiments in the millimeter-wave region.We have tried to visualize anisotropy of objects by including an anisotropy model derived from two-dimensional refractive idex ellipsoid in the image reconstruction process using a block-gradient method, which is a kind of iterative reconstruction technique. An isotropic metal patch, a wire gird with large anisotropy, and a LiNbO_3 crystal which is a typical anisotropic dielectric, were experimentally tested in the millimeter-wave region and the images were reconstructed. We have found that anisotropy of these objects are clearly imaged with a resolution of less than 1/10 of the radiation wavelength used.

本研究项目的目的是展示新型扫描近场显微镜，即扫描近场各向异性显微镜（SNAM），并使用我们提出和开发的金属狭缝型探针对扫描近场显微镜系统获得的图像进行量化，以便可视化物体的物理参数，如折射率和折射率各向异性，在毫米波和亚毫米波区域。为了更精确地量化毫米波和亚毫米波区域的图像，我们提出、设计并制作了一种新型的样品基座，以减少来自表面模式的不必要的信号波动。我们已经成功证明了这种新硬件的有效性，并发现信号波动减少到以前的10%以下。这一结果意味着我们开发的显微镜系统有可能提供优于Δn/n <$0.1的极限折射率灵敏度。此外，为了可视化物体的物理参数，我们提出了一个等效电路来描述探针和物体之间的相互作用，通过有限元法的计算机模拟和毫米波实验，成功地证明了该电路的有效性。三维折射率椭球在图像重建过程中采用块梯度法，这是一种迭代重建技术。对各向同性金属贴片、大各向异性金属丝栅和典型的各向异性介质LiNbO_3晶体在毫米波波段进行了实验测试和图像重建。我们已经发现，这些对象的各向异性清晰地成像，分辨率小于所用辐射波长的1/10。