Topology is a branch of mathematics focusing on how shapes can change without breaking or tearing. But with the discovery of the quantum Hall effect, scientists found that certain materials, called topological insulators, could also be described using a concept from topology. In these materials, a special property, known as a topological invariant, characterizes the existence of robust surface states that are immune to defects and disorder in the system.

Recently, these protected edge states were also found in photonics, where they promise robust light transfer, better data transmission, and improved optical devices. Moreover, photonic model systems can mimic the behavior of electrons in topological condensed matter. Probing into the fundamental properties of topological phases, we want to uncover insights into the collective behavior of electrons and the emergence of exotic quantum states.

Combining topology with 3D microprinting technology allows for the creation of quantum simulators, which are tiny devices that can be used for fundamental research. It also offers the unique opportunity to translate topological effects into practical applications due to the microscopic size and fast and easy fabrication of 3D microprinted systems.

Hyperspectral imaging (HSI) is an advanced analytical technique that measures a complete spectrum of light for every pixel in an image. This enables highly accurate identification of materials in applications such as agriculture, medicine, and forensic science. However, current HSI systems are typically large, complex, and have limited light sensitivity. These limitations restrict their use, particularly for sensitive samples that cannot be exposed to intense illumination. The scientific exploratory project QSCOPE addresses these challenges by establishing new scientific foundations for future photonic and quantum technologies.

To achieve this goal, colloidal quantum dots - tiny semiconductor nanocrystals with wavelength-selective absorption - are integrated into photonic three-dimensional microstructures fabricated using laser-based 3D printing. Quantum dots of different sizes are stacked vertically and arranged laterally into pixel arrays, creating sensor elements that selectively absorb different wavelengths without the need for bulky optical components. In parallel, the project investigates methods for electrically reading out the signals generated by these quantum dots.

This approach has the potential to enable smaller, faster, and more light-sensitive HSI systems that operate without cryogenic cooling, making them suitable for integration into portable devices and medical instruments. Potential applications range from the precise analysis of agricultural products and more efficient recycling processes to novel medical diagnostic technologies.

The project is carried out in collaboration with Artur Widera (RPTU) and Maria Wächtler (CAU Kiel) and is funded by the German Federal Ministry of Research, Technology and Space (BMFTR).

While (linear) 2D topological systems have already been studied in detail, relatively little is known about optical topological 3D systems. Until now, this was mainly due to limitations in the manufacturing possibilities. The technology of 3D microprinting opens up new opportunities for the investigation of complex structures in a topological context.

We also use dimensional extension in 1D photonic multilayer structures to make higher-dimensional topological physics accessible within a simple photonic platform. Such systems also offer the unique possibility to apply “unphysical” inhomogeneous magnetic fields or boundary conditions.