Publications

DOI:

10.1016/j.yofte.2025.104471External link

University Bibliography Jena:

fsu_mods_00028951External link

It has been previously observed that each core in a multi-core fiber has its own birefringence properties. Therefore, obtaining a laser output with a well-defined polarization pattern from a multi-core fiber is challenging. In this work, we explain the origin of this core-dependent birefringence and present a polarization-maintaining, 35-core fiber design that is tested in an oscillator setup, delivering over 100W of power with a polarization contrast ratio close to 10dB. This is a significant improvement with respect to a comparable non-polarization-maintaining multi-core fiber.

DOI:

10.1364/OE.579763External link

University Bibliography Jena:

fsu_mods_00030211External link

This work presents the simultaneous scaling of the average power and pulse energy emitted by multicore fiber laser systems. This is achieved through two series of experiments that use a generation of Yb-doped multicore fiber amplifiers with 49 cores, seeded by a Q-switched multicore fiber laser. One of the main results of these experiments is a total pulse energy of up to 117 mJ at a repetition rate of 5 kHz in quasi-continuous pumping operation. In a different experiment with a smaller core size multicore fiber, an average power of 400 W was achieved at a repetition rate of 5 kHz, corresponding to a pulse energy of 80 mJ in continuous pumping. The experimental results match our simulation predictions, providing valuable insights into the further energy scalability of Yb-doped multicore fibers.

DOI:

10.1364/OE.579999External link

University Bibliography Jena:

fsu_mods_00030210External link

We report the demonstration of single-frame randomized probe imaging (RPI) using a 13.5 nm extreme ultraviolet (EUV) beam from a table-top high-harmonic generation (HHG) source. Three types of beams—a smooth, vortex, and speckle beam—were used to investigate the effect of different illuminations on image quality. Single-frame RPI reconstructions were successfully achieved for all beam types, with the highest resolution of 110 nm obtained using the EUV speckle beam. Comparisons with ptychography reconstructions confirm the advantages of structured illuminations over a smooth beam, showing improved convergence and image fidelity. Furthermore, averaging a small number of RPI images reconstructed from individual diffraction patterns significantly improves the resolution to sub-100 nm. These results demonstrate the capability of single-frame RPI to deliver rapid, high-resolution EUV imaging, offering a promising approach for applications limited by acquisition time, such as ultrafast pump-probe studies and real-time feedback.

DOI:

10.1364/OE.580785External link

University Bibliography Jena:

fsu_mods_00034896External link

In this article we look at the newest developments in the understanding and mitigation of TMI in single-core fibers. This includes recent quantitative measurements that reveal the dependence of the TMI threshold on the modal content of the seed, systematic measurements on the dependence of the TMI threshold on the fiber core size, as well as the study of TMI in PM fibers including a novel passive mitigation strategy and the static modal energy transfer recently observed in these fibers.

DOI:

10.1016/j.yofte.2025.104496External link

University Bibliography Jena:

fsu_mods_00029154External link

We report on the development of a carrier-envelope phase (CEP)-stable 1030 nm fiber-based laser system producing 6.2 fs pulses achieved via the multi-pass cell (MPC) post-compression technique with 402 W average power at 100 kHz repetition rate. This system employs an upgraded three-stage MPC compression scheme exhibiting excellent beam quality properties for this intensity region. Active stabilization locks the CEP noise below 430 mrad root mean square. This work represents the first demonstration of a coherently combined fiber laser system simultaneously achieving such exceptional average power, CEP stability and sub-two-cycle pulse durations. Similar to all other light sources of the Extreme Light Infrastructure Attosecond Light Pulse Source, this newly developed system is accessible to the international research community in peer-reviewed open user calls of the Extreme Light Infrastructure European Research Infrastructure Consortium.

DOI:

10.1017/hpl.2025.10103External link

University Bibliography Jena:

fsu_mods_00035153External link

We present a theoretical evaluation of radiation dose constraints for extreme ultraviolet (EUV) and soft X-ray microscopy. Our work particularly addresses the long-standing concern regarding strong absorption of EUV radiation in biological specimens. Using an established dose–resolution model, we compare hydrated and dehydrated cellular states and quantify the fluence required for nanoscale imaging. Our analysis identifies a protein window spanning photon energies from ∼70 eV up to the carbon K-edge (284 eV). Towards the upper end of this range, at photon energies above 100 eV, EUV microscopy could in principle achieve sub-10 nm half-pitch resolution in dehydrated samples at doses well below the Henderson limit. In this situation, the radiation dose required for EUV imaging is predicted to be substantially lower than what is required for comparable resolution in water window soft X-ray microscopy. Furthermore, EUV photons with sufficiently high energy exhibit penetration depths of µm-level in dehydrated biomatter, enabling exceptional amplitude and phase contrast through thin cellular regions and small cells. These findings provide quantitative guidelines for photon energy selection and support the EUV protein window as a dose-favorable and physically viable modality for high-resolution, label-free, material-specific imaging of dehydrated biological matter.

DOI:

10.1016/j.ultramic.2026.114337External link

University Bibliography Jena:

fsu_mods_00034593External link

University Bibliography Jena:

fsu_mods_00034314External link

University Bibliography Jena:

fsu_mods_00019662External link

University Bibliography Jena:

fsu_mods_00022111External link

DOI:

10.1117/12.3042877External link

University Bibliography Jena:

fsu_mods_00024778External link

DOI:

10.1117/12.3040176External link

University Bibliography Jena:

fsu_mods_00024763External link