Project C07 - Photonic Integrated THz Image Sensor

Principal Investigators: Prof. Dr. Andreas Stöhr, UDE ZHO; Prof. Dr. Martin Hofmann, RUB PTT

The main goal of this project is to develop a photonic based 300 GHz sensor enabling 1D/2D beam steering for imaging applications. The sensor will utilize Integrated Photonic Chips (PIC) to perform THz imaging in the 300 GHz band. To our knowledge, such a continuouswave photonic based 1D/2D sensor has not been demonstrated yet.

The key innovation in this project 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 colour 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. In the first period, we aim to realize individual 1x4 transmitter and 1x4 receiver arrays pumped by the external local oscillator lasers in combination with appropriate optics for 1D beam steering. At a later stage, the operating frequency and the number of transmitter and receiver array elements will then be increased for better image resolution and 2D beam steering. Our central question is whether an efficient and compact image sensor can be realized with cost-effective 1550 nm photonic integrated chips (PICs). For this project, we combine the expertise of the group at UDE in the development of photonic millimeter-wave and THz components with that of the group at RUB on laser development and diode laser based THz imaging and spectroscopy systems. Since the sensor integration introduces several challenges in processing and integration, we will also cooperate closely on the technological level. Consequently, UDE and RUB have already transferred RUB’s plasma etching machine for deep Si and III/V waveguide etching to UDE’s cleanroom facilities.

In summary, C07 proposes a disruptive system concept for a novel 1D/2D scanning THz sensor based upon integrated photonic chips. The chips represent a key building block for the visionary mobile MARIE THz material sensor. On the technological level, the project will create national and international excellence in PIC and photonic-electronic integration mainly for imaging, but the key technologies are expected to be disruptive also for other applications such as spectroscopy or test & measurement.