Evanescent-field illumination for Terahertz biological imaging

太赫兹辐射是波长在300到100微米之间的辐射。由于它是非电离的（不像x射线），并且可以穿透许多光学不透明的介质，因此它有望用于成像。与光学成像相比，自由空间太赫兹成像的一个限制是分辨率差。提高分辨率的工业标准技术是近场光栅扫描，它将所谓的衍射极限以下的分辨率提高到几十微米。然而，这种改进是以时间为代价的。该博士研究项目将研究消褪场照明技术（通过周期结构中的全内反射和表面模式）以及最先进的太赫兹相机，以实现改进的空间分辨率，而无需近场光栅扫描。利用商用全光纤耦合太赫兹时域光谱仪和连续波IMPATT二极管光源以及太赫兹相机，博士生将设计，建模并实现高分辨率太赫兹显微镜。显微镜的成像能力将用生物样本进行测试。

Terahertz (THz) radiation is radiation with a wavelength between 300 and 100 micrometres. It holds promise for imaging since it is nonionizing (unlike X-rays) and can penetrate through many optically opaque media. A limitation of free-space THz imaging is poor resolution compared to optical imaging. The industry standard technique for improving resolution is near-field raster-scanning which improves the resolution below the so-called diffraction limit to a few tens of micrometres. However, this improvement comes at the expense of time. This PhD research programme will look at evanescent-field illumination techniques (via total internal reflection and surface modes in periodic structures) along with state-of-the-art THz cameras to achieve an improved spatial resolution without the need for near-field raster scanning. Using a commercial all fibre-coupled Terahertz time-domain spectrometer and CW IMPATT diode sources along with a THz camera, the PhD student will design, model and implement a high-resolution THz microscope. The imaging capabilities of the microscope will be tested using biological samples.