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

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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.