Sensing and Analysis of THz-Radiation using the Coherence Function (SensATion)

在电磁波的频谱中，太赫兹（THz）辐射位于微波和红外光谱之间，频率范围从100千兆赫到多太赫兹，与其他频谱制度相比，它具有许多显著的优势。虽然它是非电离的，但它可以穿透对可见光不透明的材料。此外，频率在分子振动，旋转和跃迁光谱范围内，使其非常适合检测和识别化学品和材料，例如毒品和爆炸物。在过去的几十年里，已经报道了在太赫兹范围内进行相干成像的各种方法。它们允许利用辐射的波动性质，从而实现先进的应用，如定量相对比成像，数字全息和超快速光谱。然而，目前所有在太赫兹范围内可用的相干成像技术要么基于叠加参考波场，要么基于电子门控的参考脉冲。这构成了技术水平的相当大的缺乏，因为目前没有办法表征先验未知的太赫兹辐射，例如由天线发射的，非线性光子元件，远距离的潜在自发光或恒星物体或量子光学中的非经典辐射。该项目的目标是缩小技术水平的差距，并研究和开发方法，以便在太赫兹范围内提供参考自由波场传感。该方法应基于使用剪切干涉仪对互相干函数（即空间相干）的采样。如果成功，这将首次允许在部分空间相干的情况下记录和分析先验未知的太赫兹辐射。应用范围包括光子元件、天线、自发光和远距离物体的表征，以及量子光学的研究。此外，目前在相干成像中的现有应用将在很大程度上受益于无参考技术。避免了引导和控制参考波的负担，使得新型灵活紧凑的相干成像传感器可以像相机设备一样移动。

In the spectrum of electro-magnetic waves, Terahertz (THz) radiation is located between microwaves and the infrared spectrum with frequencies ranging from 100 GHz up to multiple THz and offers a number of significant advantages compared to other spectral regimes. While being non-ionizing, it can penetrate materials which are opaque to visible light. Additionally, the frequencies are in the range of molecular vibration, rotation and transition spectra, making it well suited to detect and identify chemicals and materials such as drugs and explosives for example. In the past decades various methods for coherent imaging in the THz range have been reported. They allow to exploite the wave nature of the radiation and therefore enable advanced applications, such as quantitative phase contrast imaging, digital holography, and ultra-fast spectroscopy.However, currently all of the available coherent imaging techniques in the THz range are based either on a superposed reference wave field, or a reference pulse for electronic gating. This constitutes a considerable lack in the state of the art, because in consequence there are currently no means to characterize a priori unknown THz radiation, e.g. emitted by antennas, non-linear photonic components, potentially self-luminous or stellar objects in a far distance or non-classical radiation in quantum optics.The goal of this project is to close the gap in the state of the art and to research and develop methods in order to provide reference free wave field sensing in the THz range. The approach shall be based on sampling of the mutual coherence function (i.e. the spatial coherence) using a shear interferometer. If successful, this would for the first time allow recording and analysis of a priori unknown THz radiation even in case of partial spatial coherence. Applications would range from characterization of photonic components, antennas, self-luminous and distant objects as well as investigations in quantum optics. Furthermore, currently existing applications in coherent imaging would largely benefit from a reference free technique. Avoiding the burden of guiding and controlling a reference wave enables novel flexible and compact coherent imaging sensors that can be moved around like a camera device.