Multi‐Photon 3D Laser Micro‐Printed Plastic Scintillators for Applications in Low‐Energy Particle Physics

Plastic scintillators are inexpensive to manufacture and therefore a popular alternative to inorganic crystalline scintillators. For many applications, their advantages outweigh their lower light yield. Additionally, it is easier to structure plastic scintillators with well‐developed processing techniques which is of growing relevance in modern applications. One technique to structure plastic material is 3D printing, with noteworthy recent advances in one‐photon‐based approaches. However, some applications require high spatial resolution and optically smooth surfaces, which can be achieved by multi‐photon 3D laser micro‐printing. One application example is the improvement of sensitivity of the Karlsruhe Tritium Neutrino (KATRIN) experiment. This improvement can be realized by printing a 3D scintillator structure as an active transverse energy filter directly onto the detector. Herein, the first two‐photon printable plastic scintillator providing a printing resolution in the micrometer regime is presented. Using the benefits of two‐photon grayscale lithography, optical‐grade surfaces are achieved. The light output is estimated to be 930 photons MeV−1. A prototype structure printed directly on a single‐photon avalanche diode array is demonstrated. Many modern detector systems require structured scintillators in combination with photo‐detectors. This requirement can be fulfilled by 3D printing plastic scintillators which becomes more and more relevant. However, the resolution and surface quality of 1‐photon‐based 3D printing techniques are not sufficient for many applications. Therefore, the first multi‐photon micro‐printable scintillator is presented and its printing and scintillation capabilities are demonstrated.