Terahertz measurement system based on frequency-selective detector chips for inline industrial monitoring

该项目旨在开发基于频率选择检测器芯片的太赫兹测量系统，该系统针对在线工业监测应用。事实上，许多介电材料在太赫兹频率下具有特征光谱特征，同时是透明的，这在产品控制和认证、生物医学分析和材料识别等应用方面具有很大的潜力。到目前为止，缺乏快速的频率分辨测量技术，或者它们的价格标签，阻碍了这种应用以令人满意的方式得到解决。项目合作伙伴Toptica Photonics AG的产品“terspeed”代表了朝着这个方向迈出的一步，但它没有利用可用的光谱信息。该系统使用先进的光导发射器与成熟的光纤技术相结合产生的频谱宽太赫兹脉冲。整流肖特基二极管（SDs）用于信号检测，对几个太赫兹脉冲进行平均。光谱信息在探测过程中丢失，并且探测器受到SDs灵敏度的强本征频率滚降的影响，特别是在1太赫兹以上。鉴于上述目标应用领域，需要快速的频率选择数据采集，特别是在1thz以上的频率范围和大频谱范围内的数据采集。这是这个项目的关键点。我们的目标是将基于天线耦合半导体场效应晶体管（所谓的TeraFETs）的太赫兹探测器带入测量系统。在许多申请人的项目中，如之前的dfg资助项目，terafet已被证明是高效的太赫兹探测器。虽然sd代表低于1thz的最先进技术，但这个角色已经转移到1thz以上的terafet。terafet的频率衰减要弱得多，对1太赫兹以上的SDs的灵敏度更高，灵敏度范围可达数太赫兹。现有的terspeed平台及其光电源将通过使用TeraFET探测器进行扩展，频率选择性要么内在地结合在TeraFET的窄带谐振天线设计中，要么外部地通过使用由频率选择表面制成的窄带滤波器结构与宽带TeraFET结合使用。因此，terspeed的系统概念将扩展到多光谱太赫兹测量系统。其功能将通过与应用相关的光谱测量来证明，其中将包括在在线情况下快速记录产品认证的安全特性。

The project aims at the development of a THz measurement system based on frequency-selective detector chips, the system targeting inline industrial monitoring applications. The fact that many dielectric materials have characteristic spectral features at THz frequencies and simultaneously are transparent, holds much potential for applications such as product control and authentication, biomedical analysis and material identification. Until now, the lack of fast frequency-resolved measurement techniques, or their price tag, have prevented such applications to be addressed in a satisfactory manner.The product “TeraSpeed” of the project partner Toptica Photonics AG represents a step in this direction, but has the shortcoming that it doesn’t utilize the available spectral information. The system works with spectrally broad THz pulses generated with advanced photoconductive emitters in combination with a mature optical fiber technology. Rectifying Schottky diodes (SDs) are employed for signal detection, averaging over several THz pulses. The spectral information is lost in the detection process and the detectors suffer from the strong intrinsic frequency roll-off of the sensitivity of the SDs notably above 1 THz.With the view towards the target application fields mentioned above, fast frequency-selective data acquisition especially in the frequency regime above 1 THz and over a large spectral range is a requirement. This is the pivotal point of this project. We aim to bring THz detectors based on antenna-coupled semiconductor field-effect transistors (so-called TeraFETs) into the measurement systems. In a number of the applicant’s projects such as the preceding DFG-funded project, TeraFETs have proven to be highly efficient THz detectors. While SDs represent the state-of-the-art below 1 THz, this role has gone to TeraFETs above 1 THz. TeraFETs have a much weaker frequency role-off and are superior in sensitivity to SDs above 1 THz, with a sensitivity range reaching multiple THz.The existing TeraSpeed platform with its optoelectronic source will be expanded by the use of TeraFET detectors, the frequency selectivity either being incorporated intrinsically in the narrowband, resonant antenna design of the TeraFETs, or extrinsically by the use of narrow-band filter structures made from frequency-selective surfaces to be used in combination with broadband TeraFETs. The system concept of the TeraSpeed will thus be extended into that of a multispectral THz measurement system. Its functionality will be demonstrated by application-relevant spectroscopic measurements, among which will be the rapid recording of security features for product authentication in an inline situation.