14 Jan. 12 years of nonlinear photonics: collaborative research completed
After the maximum possible duration of three funding periods, the Collaborative Research Center CRC/TRR 142 „Tailor-made Nonlinear Photonics: From Fundamental Concepts to Functional Structures” was completed in December 2025. A total of 210 scientists were involved in the 12 years of research. The total funding amounted to 35 million euros.
Nonlinear effects for future applications
Prof. Thomas Zentgraf, spokesperson for the Collaborative Research Center, provided an overview of 12 years of CRC TRR 142. Image: University of Paderborn, Besim Mazhiqi
The aim of the Collaborative Research Center (CRC) was to research, develop, and construct nonlinear photonic systems. When light and matter interact, linear effects change the incident light. Examples include reflection and scattering. However, the wavelengths remain the same. With a laser, it is different: it enables the generation of nonlinear effects such as frequency doubling. According to those involved, TRR 142 has produced concepts for making novel nonlinear functionalities from the fields of materials physics and quantum photonics usable for applications in the field of future information and communication technologies.
Moving beyond fundamental research
“We wanted to take nonlinear optical and quantum effects from the stage of basic physics research and put them into practical application,” says Prof. Thomas Zentgraf from the Department of Physics at the University of Paderborn, spokesperson for the SFB. According to Zentgraf, this involved combining the core competencies of the University of Paderborn in the fields of photonic materials, solid-state technology, quantum optics, and theory with those of TU Dortmund University in nonlinear spectroscopy and instrumentation. The team focused on tailoring nonlinear interactions, controlling quantum systems, light emission and propagation, and nonlinearities at the single-photon level. “TRR 142 has contributed significantly to the further development of nonlinear photonics and quantum optics and, with its interdisciplinary cutting-edge research, has laid the foundations for promising technologies,” says University President Prof. Matthias Bauer.
Results were also presented during a poster session. Image: University of Paderborn, Besim Mazhiqi
Tap-proof communication through manipulation
One application of SFB research is encrypted, tap-proof communication. To encode the transmitted data, the researchers have specifically modified optical properties, among other things. To this end, they have developed metasurfaces. Until now, materials were neither designed nor sufficiently researched for efficient use. “They consist of artificially produced structures whose optical, magnetic, or electrical properties do not occur in nature. Their advantage is that they can refract and even change radiation,” says Zentgraf. “This allows new frequencies to be achieved that would not be possible without targeted manipulation.”
This arrangement of nanostructures on surfaces has enabled the creation of artificial materials whose linear and nonlinear optical behavior can be adjusted. Their functionality goes far beyond that of conventional materials. This enables compact optical components for frequency conversion or control of light propagation. Research in the field of quantum photonics focused on quantum communication, quantum sensing, and quantum information processing. Integrated optics provided an important basis for implementation. For example, the development of efficient waveguides for frequency conversion. According to the researchers, the targeted use of these technological developments has enabled the realization of integrated optical frequency converters, quantum light sources, and nonlinear interferometers, which are indispensable key components for optical quantum technologies.
Quantum dots and quantum teleportation
Quantum technologies offer many novel possibilities for processing and transmitting information and performing precise measurements. As the protection of sensitive data and information becomes increasingly important, corresponding communication networks are gaining in significance. Semiconductor quantum dots can play an important role here. Quantum dots behave like artificial atoms: with precise laser excitation, they can be used to control individual photons with great accuracy and to create single-photon sources, which are essential for secure quantum communication. In addition to producing such structures, the physicists in Paderborn have also succeeded in realizing so-called quantum teleportation with the aid of imperfect quantum dots, i.e., artificial material structures. In this process, the state of one photon is transferred to another. The sender and receiver become entangled with each other. This requires sources that produce indistinguishable photons.
The closing event provided another opportunity for discussions about the Collaborative Research Center. Image: University of Paderborn, Besim Mazhiqi
Research for the future
Collaborative Research Centers are long-term research institutions at universities where scientists work together on interdisciplinary research programs. They enable innovative, challenging, complex, and long-term research projects to be carried out by coordinating and concentrating people and resources at the applicant universities. They are funded by the German Research Foundation (DFG) for a period of up to 12 years, with each funding period lasting four years.
Information on the TRR is available at: trr142.uni-paderborn.de
Source: www.uni-paderborn.de
Image: University of Paderborn, Besim Mazhiqi