Compact Polarimetric THz Sensor for Reflectometric Imaging

太赫兹(THz)波段的独特特性，例如太赫兹波的非电离能级，再加上微米级的波长，在传感、光谱和成像应用中提供了关键的优势。例如，分子共振的吸收特征在太赫兹波段丰富，使关键的遥感和光谱技术能够用于天文学、宇宙学、物理学和化学的科学研究。然而，现代的太赫兹光谱和成像工具依赖于单极化传感器，因此，传感的太赫兹信号中的重要偏振信息经常丢失。在这个项目中，将开发一种全极化太赫兹传感器，这将首次通过利用太赫兹波的偏振特性，为太赫兹光谱和成像提供一种全新的模式。极化太赫兹成像和相关的传感器硬件可以通过利用极化数据来改变太赫兹成像的范例。必须指出的是，“偏振测量”在射频、微波和光学频段中的影响不可低估，因为关键应用影响到社会的许多方面。例如，偏振雷达保护我们免受入侵者的侵扰，光学椭偏仪通常用于固态材料工程的许多领域，包括价值数十亿美元的半导体工业。这里提出的全极化太赫兹传感器和相关的太赫兹光谱偏振测量工具将在生物医学传感、化学光谱和药物评价等急需领域引入新的传感和成像应用。此外，拟议的工作将产生一个实验室规模的光谱学工具，该工具可以很容易地纳入学术课程，作为动手实验和培训试验台，以激励学生在STEM领域继续他们的教育。特别是，拟议的工作将首次实现在100 GHz至5 THz频段具有辐射模式和偏振纯度的新型光导天线阵列，与脉冲和/或连续波激光源集成，以产生宽带或可调的全极化THz波段源和探测器，图像分辨率和光谱灵敏度提高3倍。随着这些新型传感器的问世，将首次展示以太赫兹反射图像形式的偏振传感数据。作为一种最相关和最具社会影响的应用，在由于结合水含量相似而健康组织和恶性组织的材料特性彼此非常接近的情况下，将追求使用THz旋光仪进行癌症边缘检测和识别。利用该传感器的全极化特性，该传感器获得的太赫兹图像具有显著改善的对比度，因此新传感器所提供的额外自由度将显著增强传统的太赫兹成像。此外，这里建议的紧凑型传感器拓扑结构将与内窥镜应用相称，并可能在完成建议的工作后进行临床试验。

Unique properties of the Terahertz (THz) band such as the non-ionizing energy levels of THz waves, coupled with micrometer-scale wavelengths offer key advantages in sensing, spectroscopy, and imaging applications. For example, absorption signatures of molecular resonance are rich in the THz band and enable key remote sensing and spectroscopy techniques for scientific research in astronomy, cosmology, physics and chemistry. Nevertheless, contemporary THz spectroscopy and imaging tools rely on single-polarization sensors, thus, vital polarimetric information in the sensed THz signals is often lost. In this project, a fully-polarimetric THz sensor will be developed, which will enable, for the first time, an entirely new modality for THz spectroscopy and imaging by harnessing the polarization properties of THz waves. Polarimetric THz imaging and the associated sensor hardware could change the paradigm for THz imaging by harnessing polarimetric data. It is important to note that the impact of "polarimetry" in the RF, microwave as well as optical bands cannot be understated, with key applications impacting many aspects of society. For example, polarimetric radars keep us safe from intruders and optical ellipsometers are routinely used in many areas of solid state materials engineering, including the multi-billion-dollar semiconductor industry. The fully-polarimetric THz sensor and the associated THz-spectroscopic polarimetry tools proposed here will usher in new sensing and imaging applications in the much-needed areas of biomedical sensing, chemical spectroscopy and pharmaceutical evaluation, to name a few. In addition, the proposed work will result in a laboratory-scale spectroscopy tool that can be readily incorporated into the academic curriculum to serve as a hands-on experimentation and training testbed to inspire students to pursue their education in STEM fields.In particular, the proposed effort will realize, for the first time, novel photoconductive antenna arrays with radiation pattern and polarization purity over the THz frequency band spanning from 100 GHz to 5 THz, integrated with pulsed and/or continuous-wave laser sources to generate wideband, or tunable, fully-polarimetric THz-band sources and detectors with 3-times improved image resolution and improved spectral sensitivity. With the availability of these novel sensors, first-ever polarimetric sensing data in the form of THz reflectometric images will be demonstrated. As a most relevant and high-societal-impact application, cancer margin detection and identification using THz polarimetry will be pursued where the material properties of the healthy and malignant tissues are very close to each other due to similar bound water content. With the full-polarimetric nature of the proposed sensor, THz images obtained by the proposed sensor exhibits significantly improved contrast and thus conventional THz imaging will be significantly enhanced by the additional degrees-of-freedom afforded by the new sensor. Moreover, the compact sensor topology proposed here will be commensurate with endoscopic applications and could likely result in a clinical trial upon the completion of the proposed effort.