Periodic Reporting for period 1 - PhoVeNA (Photonic Vector Network Analyzers)
Reporting period: 2024-06-01 to 2025-11-30
The deployment of 5G networks and the upcoming deployment of 6G in the next decade is essential to advance wireless communication for keeping pace with modern data hunger. While 6G will start with microwave bands, future 6G will incorporate first channels in the Terahertz domain (100 GHz -10 THz). However, terahertz technology in communication applications has a main bottle neck: the lack of powerful sources and versatile components. In order to engineer these towards maturity, sophisticated characterization tools are required to identify design flaws. The most prominent of these are Vector Network analyzers (VNAs), a class of systems currently dominated by electronics. Meanwhile, photonic technologies start to become competitive with established electronic technologies in the lower THz band and already excel beyond 1 THz in terms of dynamic range. Optical comb technologies enable frequency accuracy and stability beyond that of electronic systems, potentially at a fraction of the cost. This project aims for the development of two photonic prototype systems: (i) a photonic frequency extender for the WR10 band, compatible with electronic base band VNAs and (ii) a completely photonic system based on a frequency comb with a bandwidth of several THz, spectral purity comparable to or better than that of electronic VNAs and seamless tunability over the whole range. The technology to be developed in this project will simplify characterizing devices over a larger frequency range at (much) lower cost, enabling large scale deployment of VNA systems. This will, in turn, foster development of Terahertz systems for further key applications besides communication, e.g. in spectroscopy, including medical applications, industrial scale non-destructive testing and quality control as well as security.
The proposal targeted for two protoypes. Prototype 1 is a photonic frequency extender consisting of an electro-optic continuous-wave comb driving a set of photomixers/photoconductors. We successfully completed the optical subsystem and the assembly of several photoconductors in a WR10 package. The photonic extender was successfully tested at the premises of Rohde & Schwarz GmbH & Co. KG, attached to a commercial microwave base unit. As a proof of concept, we characterized filter structures and compared the results to purely electronic measurements.
Prototype 2 is a fully photonic system. We successfully carried out preliminary tests with ATLAS/Toptica Terascan Ultra at industrial partner TOPTICA Photonics SE. The laser signal generated by the frequency-comb-based ATLAS system drove a photonic source-receiver pair in order to measure S21 with sub-kHz precision. As test object, we used a low-pressure gas cell with water and ammonia vapor. Both gas types were successfully characterized down to the Doppler-limited linewidth. The results became an integral part of the Nature Communications publication https://doi.org/10.1038/s41467-025-66457-6(opens in new window).
Prototype 2 is a fully photonic system. We successfully carried out preliminary tests with ATLAS/Toptica Terascan Ultra at industrial partner TOPTICA Photonics SE. The laser signal generated by the frequency-comb-based ATLAS system drove a photonic source-receiver pair in order to measure S21 with sub-kHz precision. As test object, we used a low-pressure gas cell with water and ammonia vapor. Both gas types were successfully characterized down to the Doppler-limited linewidth. The results became an integral part of the Nature Communications publication https://doi.org/10.1038/s41467-025-66457-6(opens in new window).
Purely photonic vector network analyzers offer the capability to cover a large share of the microwave and THz spectrum (few 10 GHz to several THz) within a single system, without the need of extenders. This would make the system very versatile and drastically reduces system price, offering new commercial pathways beyond current niche applications. Mixed photonic-electronic systems are less expensive beyond a few 100 GHz than their electronic counterparts and inherit the performance, software and evaluation capabilities of the microwave base unit. For future commercialization, we realized that a better out-of-band rejection of the optical subsystem is necessary to improve suppression of undesired comb side bands.
In short, we have achieved the following scientific and technical results:
-Electro-optic comb laser system for driving photonic devices at WR10 with Hz-level spectral purity
-Full compatibility of a photonic frequency extender to an electronic microwave base unit
-A fully photonic system with sub-kHz spectral resolution below 1 THz and frequency coverage of several THz.
In short, we have achieved the following scientific and technical results:
-Electro-optic comb laser system for driving photonic devices at WR10 with Hz-level spectral purity
-Full compatibility of a photonic frequency extender to an electronic microwave base unit
-A fully photonic system with sub-kHz spectral resolution below 1 THz and frequency coverage of several THz.