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Highlighted authors are members of the University of Jena.

  2. Polarization-maintaining, rod-type, ytterbium-doped, multi-core fiber for high power operation

    Year of publicationPublished in:Optics Express Y. Khalil, C. Jauregui, A. Klenke, M. Bahri, J. Nold, N. Haarlammert, T. Schreiber, J. Limpert
    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.
    University Bibliography Jena:
    fsu_mods_00030211External link

  3. 117-mJ pulse energy, high average power, Q-switched Yb-doped 49-core fiber amplifier

    Year of publicationPublished in:Optics Express M. Bahri, C. Jauregui, A. Klenke, M. Lenski, J. Nold, N. Haarlammert, T. Schreiber, J. Limpert
    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.
    University Bibliography Jena:
    fsu_mods_00030210External link

  4. Recent developments in the understanding and passive mitigation of transverse mode instability

    Year of publicationPublished in:Optical Fiber Technology: Materials, Devices, and Systems C. Jauregui, Y. Tu, S. Kholaif, F. Möller, G. Palma-Vega, N. Haarlammert, T. Walbaum, T. Schreiber, J. Limpert
    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.
    University Bibliography Jena:
    fsu_mods_00029154External link

  5. Over 400 W average power, sub-two-cycle, carrier-envelope phase-stable fiber laser system

    Year of publicationStatusReview pendingPublished in:High Power Laser Science and Engineering I. Seres, E. Shestaev, M. Tschernajew, P. Jójárt, C. Gaida, N. Walther, T. Bartyik, B. Gilicze, Z. Bengery, D. Hoff, M. Kienel, T. Eidam, J. Limpert, Á. Börzsönyi, K. Varjú, Z. Várallyay
    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.
    University Bibliography Jena:
    fsu_mods_00035153External link

  6. Dose constraints for high-resolution imaging of biological specimens with extreme ultraviolet and soft X-ray radiation

    Year of publicationPublished in:Ultramicroscopy C. Liu, L. Licht, J. Rothhardt
    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.
    University Bibliography Jena:
    fsu_mods_00034593External link

  8. Pulse energy scaling of ultrafast lasers via spectral-temporal shaping and coherent combination

    Year of publication L. Stark
    University Bibliography Jena:
    fsu_mods_00019662External link

  11. Precision manufacturing of multicore fibers for superior fiber laser performance

    Year of publicationPublished in:Fiber Lasers XXII: Technology and Systems N. Haarlammert, J. Nold, S. Kuhn, C. Jauregui, J. Limpert, T. Schreiber
    University Bibliography Jena:
    fsu_mods_00024763External link

  12. Influence of core size on the transverse mode instability threshold of fiber amplifiers

    Year of publicationPublished in:Optics Express S. Kholaif, C. Jauregui, J. Nold, N. Haarlammert, S. Kuhn, T. Schreiber, J. Limpert
    We present what we believe to be the first systematic experimental study investigating the impact of core size on transverse mode instability. This is a very complex measurement that requires a significant amount of attention to detail. For example, this study can only be done using fibers which modal characteristics do not change with the core size, a property offered by Ytterbium-doped large-pitch fibers. Additionally, it is mandatory to consider the influence of gain saturation and photodarkening to isolate the impact of the core size on the transverse mode instability threshold. The findings of the measurements reveal that the dependence of this threshold with the core size is weaker than predicted by some theoretical models. Additionally, during the course of these measurements, a mode instability threshold over 600 W was achieved in one of the fibers, which represents the highest, diffraction-limited, average output power reported from an Ytterbium-doped, rod-type fiber so far.
    University Bibliography Jena:
    fsu_mods_00029704External link
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