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 GHz到多个THz，与其他光谱区域相比具有许多显著的优点。虽然是非电离的，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。在过去的几十年中，已经报道了用于太赫兹范围内的相干成像的各种方法。它们允许利用辐射的波动性质，因此能够实现高级应用，例如定量相衬成像、数字全息术和超快光谱学。然而，目前所有可用的太赫兹范围内的相干成像技术都是基于叠加的参考波场或用于电子门控的参考脉冲。这在现有技术中构成了相当大的不足，因为结果是目前没有手段来表征先验未知的THz辐射，例如由天线、非线性光子组件、潜在的自发光或恒星物体在遥远的距离或非-量子光学中的经典辐射。该项目的目标是缩小现有技术中的差距，并研究和开发方法，以便提供THz范围内的参考自由波场感测。该方法应基于使用剪切干涉仪对互相关函数（即空间相干性）进行采样。如果成功，这将首次允许记录和分析先验未知的THz辐射，即使在部分空间相干的情况下。应用范围将从光子元件，天线，自发光和遥远的物体以及量子光学研究的表征。此外，相干成像中的当前现有应用将在很大程度上受益于无参考技术。避免引导和控制参考波的负担使得能够实现新颖的灵活且紧凑的相干成像传感器，其可以像相机设备一样四处移动。

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.