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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CELTA (Convergence of Electronics and Photonics Technologies for Enabling Terahertz Applications)

Teaser

Summary

Societal relevance: securing that the food we consume is free of poisonous substances, securing that medicines are not falsified and being able to early detect diseases such as cancer, are a few examples of applications of Terahertz technologies. The ITN CELTA aims to produce the next generation of researchers who will enable Europe to take a leading role in the multidisciplinary area of utilizing Terahertz technology for applications involving components and complete systems for sensing, instrumentation, imaging, spectroscopy, and wireless communications. Within CELTA, fifteen early stage researchers are working towards the realization of three demonstrators: beam steering technology for communication applications, a photonic vector analyzer for spectroscopy and materials characterization, and a THz imager for sensing applications.

The problem tackled. For the three demonstrators considered in CELTA, a common technological challenge is achieving high enough power level of Terahertz radiation at the transmitter side and performing high sensitivity detection at the receiver side. Another challenge of Terahertz technologies is compact, small size and portable solutions, preferable with user friendly interfaces. Increasing the resolution and reliability of imaging realized by Terahertz cameras is a timely and relevant challenge. All the three above-mentioned challenges are tackled within the ITN CELTA.

Overall objectives: To face the challenge of power levels for THz generation and high sensitivity of THz receivers, the following objectives are pursued in CELTA. Firstly, transmitter and receiver configurations including combination of beam steering and beamforming using antenna arrays, phase shifting, envelope detectors, and an optical true time delay network are considered. Furthermore, high power amplification and multiple stages of frequency multiplication are also considered. A free-space THz vector network analyzer (VNA) using optical fiber coupled and compact THz elements is developed as a small size and portable solution. A fine tunable THz transmitter as well as a compact and highly sensitive THz detector are developed serving the objective of compactness and high-resolution for imaging and THz-VNA analysis. Finally, the challenge of increasing resolution and reliability of THz cameras is tackled by a combination of large pixel array THz cameras in combination with advanced signal processing algorithms.

Work performed

Progress is made in all the sub-systems required for the three demonstrators developed in CELTA.

Regarding the beamforming demonstrator advances have been centered in the design of an integrated circuit for optical true time delay beamforming. Its preliminary feasibility was validated using discrete components and multi-core optical fibers. A dielectric rod waveguide-based phase-shifters with integrated carbon nanotube layers have been simulated, fabricated and measured in the frequency range 75â€“500 GHz. Circularly polarized antennas in a substrate integrated waveguide technology has also been designed, analyzed and manufactured. Another component that has been designed is a leaky wave antenna (LWA) with frequency/electrically scanning capability of main beam over a wide angular range.

Regarding the sub-systems of THz electronics for the vector network analyzer (THz-VNA) and THz imager, new results are related to the design of frequency doublers at 280 GHz and frequency triplers at 549 GHz with high rejection of undesired harmonics. Furthermore, a 183 GHz and a 366 GHz voltage-controlled oscillator was designed with output power of 3 dBm, tuning range of 11 GHz and an expected low phase noise. A solid-state power amplifier based a common emitter configuration at 160 GHz was design. It exhibits remarkable features: high output power up to 15 dBm, power efficiency of 11% and gain of 26 dB. New progress has also been made developing electro-optical comb scheme for signal generation a detection in the sub-THz range. Schemes based on phase modulation, dual comb generation and mode-locking/mode-picking through optical injection locking were demonstrated within a remote dual comb detection .
Terahertz photonic generation has also offered important advances with the first prototypes of graphene-hybrid electrode based photomixers. For some of those devices, a packaging architecture for plug-and-play operation has been developed as well as experiments for determining their noise equivalent power (for receivers) and their emitted power (as transmitters).

The progress towards the Terahertz imager demonstrator is highlighted by the design and manufacturing of two different types of THz arrays (6x7 pixels and 12x12 pixels) . They were tested at room temperature and at 80 K showing state-of-the-art performance for quasi-optical detectors. THz camera electronics has also been developed. A new concept of a compact sensor based on interferometric transmission measurement applicable for near-field scanning microwave microscopy measurements was suggested and experimentally verified in frequency range 45 MHz â€“ 20 GHz. Also, a continuous-wave Terahertz off-axis digital holographic system has been built. And sparsity based compression technique has been introduced before numerical data reconstruction in order to reduce the dataset required for hologram reconstruction.

Final results

The experimental validation of hybrid photonic/millimeter wave systems with beam-steering capabilities has been carried out that paved the way for a new optical beamformer chip design, that together with the new design of a dielectric rod waveguide-based antenna array are remarkable novel results towards the implementation of an agile beam-forming system. Another issue address is the possibility to achieve high gain and wide scanning angles. Hence, the results we expect by the end of the project is a system with broadband operation, small size, that is also energy efficient and reconfigurable.

THz electronics achievements concerns frequency doublers an triplers with high quality performance, as well as voltage controlled oscillators, that together with a novel graphene-hybrid electrode based photomixers constitutes a novel hybrid electrode structure for realizing the THz-VNA demonstrator. The expected of the project, photonic optical combs will be included in the overall architecture and therefore we expect that a a complete THz-VNA system to perform beyond the-state-of-the-art.

THz imaging is the third main experimental demonstrator of the project. Within this area, two THz detection arrays were designed, fabricated and successfully tested as well as electronics for the cameras showing performance at the edge of what is possible today, including holographic capabilities. Planned work includes using plasmonic detectors to achieve high resolution THz cameras, MIMO radars in the THz range, new SiGe BJTs amplifiers, interferometry in the sub-THz region, as well as signal processing software to retrieve and interpret what the imaging system captures, particularly to include the holographic feature.
All three demonstrators have the potential to be taken over for higher technology readiness levels (TRL) with view of test in realistic end-user conditions and therefore be considered for commercialization. The prospects of use of such THz products in metrology, sensing and communications would be of large impact due to their compact, potential low cost and high performance parameters.