Mobile Material Characterization and Localization by Electromagnetic Sensing


More than 100 years ago, scientists invented the mobile camera to take pictures at any location. More than 30 years ago, engineering scientists invented the mobile phone to make calls anywhere. Now it is time to invent a mobile material detector to determine materials of any surface as well as inside an object at any location.

All of these inventions are based on technological advances that enable electronic components to reach a complete system through integrated circuits. Compared to today's voluminous and static material detectors, a mobile material detector enables numerous new applications: locating autonomous fireplaces and unconscious people in smoky, burning buildings, reliably detecting cables and objects inside walls, or more generally, to systematically generate material cards, for example, to find and classify objects in any environment. MARIE's selected lower measurement frequency corresponds to the current state of research for compact mobile transmitters and receivers with 250 GHz; The targeted upper measurement frequency is 4 THz, in order to be able to identify a variety of materials due to their specific absorption lines.

Compact Optoelectronic THz Spectroscopy System

Time Domain Spectroscopy (TDS) is the gold standard for material characterization in the frequency range of 100 GHz to a few THz. However, typical TDS systems are complex and operate in a laboratory environment only. For the long-term vision of MARIE, a compact and portable TDS system is necessary. This subproject aims at developing such a compact and portable THz system for material inspection by taking a Quasi TDS (QTDS) approach. The main difference in our system is the multimode operation of the diode lasers in contrast to the more demanding mode-locked operation of solid-state or fiber lasers. During the subproject, we will investigate the complex interplay of multimode diode lasers and optoelectronic components for THz generation and detection. We will then proceed to develop a quasi-time domain spectroscopy system, which incorporates all these findings making use of well-established telecommunication diode laser technology at 1550 nm. This QTDS system will be used to efficiently measure spectral fingerprints up to frequencies around 1 THz.

Photonic Integrated THz Image Sensor

The main goal of this subproject is to develop a photonic based 300 GHz sensor enabling 1D/2D beam steering for imaging applications. The sensor will utilize Photonic Integrated Chips (PICs) to perform THz imaging in the 300 GHz band. To our knowledge, such a continuous-wave photonics-based 1D/2D sensor has not been demonstrated yet. The key innovation in this subproject is the development of an integrated photonic THz beam steering chip using an Optical Beam Forming Network (OBFN) with high-power Triple Transit Region Photodiodes (TTR-PD) for THz generation and InGaAs mixers with and without integrated PDs for the optical LO. For homodyne operation, a phase-stable two color diode laser system with 300 GHz difference frequency will be developed and adapted to serve as an optical local oscillator. We will combine the components and demonstrate a coherent 300 GHz imaging sensor. To avoid time-consuming mechanical scanning, we will use arrays of transmitters and receivers for beam steering.

Further information: SFB / TRR 196 MARIE

Contact: Andreas Stöhr