Sonstige Publikationen

2021

H. Stark, J. Buldt, M. Müller, A. Klenke, and J. Limpert
100 fs pulses directly from a kW-class mJ-level ytterbium-doped fiber CPA laser system
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
S. E. Kholaif, Y. Tu, C. Stihler, C. Jauregui, and J. Limpert
Characterization of transverse mode instability in fiber-laser systems using a position-sensitive detector
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
M. Gebhardt, T. Heuermann, R. Klas, A. Kirsche, C. Liu, Z. Wang, M. Lenski, C. Gaida, C. Jauregui, J. Antonio-Lopez, A. Schulzgen, R. Amezcua-Correa, J. Rothhardt, and J. Limpert
High repetition rate high-order harmonic generation up to the carbon K-edge in an antiresonant hollow-core fiber
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
C. Jauregui-Misas, C. Stihler, S. E. Kholaif, Y. Tu, and J. Limpert
Mitigation of transverse mode instability in polarization maintaining, high-power fiber amplifiers
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
C. Stihler, C. Jauregui, S. E. Kholaif, Y. Tu, and J. Limpert
Mitigation of transverse mode instability through a dynamic modification of the inversion in high-power fiber amplifiers
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
A. Steinkopff, C. Jauregui, C. Aleshire, A. Klenke, and J. Limpert
Optimizing the design of coherently combined multicore fiber amplifiers
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
G. Palma-Vega, C. Hupel, J. Nold, S. Kuhn, J. Limpert, N. Haarlammert, and T. Schreiber
Simplified manufacturing of advanced microstructured fibers for laser applications
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI
W. Eschen, V. Schuster, S. Wang, L. Loetgering, C. Liu, R. Klas, J. Limpert, and J. Rothhardt
Ultrafast nanoscale XUV table-top coherent diffractive imaging
Frontiers in Ultrafast Optics: Biomedical, Scientific, and Industrial Applications XXI (March 2021)
DOI

2020

M. Stapelfeld, F. Schmidl, P. Seidel, S. Stück, V. Tympel, T. Stöhlker, D. Haider, M. Schwickert, T. Sieber, M. Schmelz, T. Schönau, and R. Stolz
The Dual-Cryogenic Current Comperator (DCCC) as a new Prototype CCC for Beamline Monitoring
2020 IEEE SENSORS (December 2020)
DOI
M. Mueller, C. Aleshire, H. Stark, J. Buldt, A. Steinkopff, A. Klenke, A. Tünnermann, and J. Limpert
10.4 kW coherently-combined ultrafast fiber laser
Proc. SPIE, 11260 :112600B (February 2020)
Abstract:
We present a coherently-combined ultrafast fiber laser system consisting of twelve amplifier channels delivering 10.4 kW average power at 80 MHz repetition rate with a pulse duration of 240 fs FWHM and an almost diffraction-limited beam quality of M2 ≤ 1.2. The system incorporates an automated self-adjustment of the beam combination with 3 degrees of freedom per channel. The system today is, to the best of our knowledge, the world's most average-powerful femtosecond laser. Thermographic analysis indicates that power scaling to 100 kW-class average power is feasible.
Z. Wang, T. Heuermann, M. Gebhardt, C. Gaida, C. Jauregui, and J. Limpert
108 W average power ultrashort pulses with GW-level peak power from a Tm-doped fiber CPA system
Proc. SPIE, 11260 :112600K (February 2020)
Abstract:
Applications such as material processing, spectroscopy, particle acceleration, high-harmonic and mid-IR generation can greatly benefit from high repetition rate, high power, ultrafast laser sources emitting around 2 μm wavelength. In this contribution we present a single-channel Tm-doped fiber chirped-pulse amplifier delivering 108 W of average output power at 417 kHz repetition rate with 250 fs pulse duration and 0.73 GW of pulse peak power. To the best of our knowledge, this is the first demonstration of an ultrafast Tm-doped fiber laser with more than 100 W of average power and GW-level peak power.
A. Steinkopff, C. Jauregui, A. Klenke, C. Aleshire, A. Tünnermann, and J. Limpert
Investigation of the thermo-optical behavior of multicore fibers used in coherently combined fiber laser systems
Proc. SPIE, 11260 :112600D (February 2020)
Abstract:
In this work we present theoretical investigations of the power scaling potential of multicore fibers. In principle it is widely accepted that increasing the number of active cores helps to overcome current challenges such as transversal mode instabilities and non-linear effects. However, in order to do a proper analysis of the average power scaling potential of multicore fibers it is required to pay particular attention to thermal effects arising in such fibers. Therefore, a simulation tool has been developed that is capable of solving the laser rate equations, taking into account the resulting temperature gradient and the distortions in the mode profiles that it causes. In the study several different multicore fibers possessing a rectangular core position layout of 2×2 to 7×7 of active cores have been analyzed. Moreover, we have investigated the influence of the active core size in terms of thermal effects as well as the extractable output power and energy. This includes a study in the maximum achievable coherent combination efficiency of the multicore channels (that is strongly influenced by the distorted mode profile at the fiber end facet), the impact on nonlinear effects, the optical path differences between the cores and the amplification efficiency which are all triggered by thermal effects. Finally the scaling potential as well as the challenges of such fibers will be discussed.
C. Jauregui, C. Stihler, Y. Tu, S. Kholaif, and J. Limpert
Mitigation of transverse mode instability with travelling waves in high-power fiber amplifiers
Proc. SPIE, 11260 :112601A (February 2020)
Abstract:
In this work we present a novel way to mitigate the effect of transverse mode instability in high-power fiber amplifiers. In this technique a travelling wave is induced in the modal interference pattern by seeding the amplifier with two modes that have slightly different frequencies. The interference pattern thus formed will travel up-or downstream the fiber (depending on the sign of the frequency difference between the modes) with a certain speed (that depends on the absolute value of the frequency difference). If the travelling speed is chosen properly, the thermally-induced index grating will follow the travelling modal interference pattern creating a constant phase shift between these two elements. Such a constant controllable phase shift allows for a stable energy transfer from the higher-order modes to the fundamental mode or viceversa. Thus, this technique can be adjusted in such a way that, at the output of the fiber almost all the energy is concentrated in the fundamental mode, regardless of the excitation conditions. Moreover, this technique represents one of the first examples of the new family of mitigation strategies acting upon the phase shift between the modal interference pattern and the refractive index grating. Additionally, it even exploits the effect of transverse mode instability for gaining control over the beam profile at the output of the amplifier. Therefore, by adjusting the frequency difference between the seed modes, it is possible to force that the beam at the output acquires the shape of the fundamental mode or that of a higher order mode.
C. Aleshire, A. Klenke, M. Müller, H. Stark, A. Tünnermann, and J. Limpert
Simplification strategies for segmented-mirror splitters in multicore fiber CBC systems
Proc. SPIE, 11260 :112600E (February 2020)
Abstract:
A simplification of segmented-mirror splitters for coherent beam combination based on numerical optimization of coating designs is presented. The simplified designs may facilitate the production of such elements for coherent beam combination while maintaining high combination efficiency. The achievable efficiency and error tolerance, and additional performance characteristics are analyzed in the context of coherently combined multicore fiber laser systems.
M. Gebhardt, T. Heuermann, Z. Wang, M. Lenski, C. Gaida, R. Klas, A. Kirsche, S. Hädrich, J. Rothhardt, and J. Limpert
Soft x-ray high order harmonic generation driven by high repetition rate ultrafast thulium-doped fiber lasers
Fiber Lasers XVII: Technology and Systems (February 2020)
DOI
C. Jauregui, A. Steinkopff, and J. Limpert
Talbot Fiber: a poorman's approach to coherent combining
Proc. SPIE, 11260 :1126011 (February 2020)
Abstract:
In this work we present a multicore fiber design that exploits the Talbot effect to carry out the beam splitting and recombination inside of the fiber. This allows reducing the complexity of coherent combining systems since it makes the splitting and combining subsystems together with the active stabilization redundant. In other words, such a multicore fiber behaves for the user as a single core fiber, since the energy is coupled just in a single core and it is extracted from the same core. This work describes the operating principle of this novel fiber design and analyzes its performance in high power operation using a simulation model based on the supermode theory. This includes a study on the impact on non-linear effects, on the amplification efficiency, on the thermal resilience of this design and on the performance dependence on the pump direction. Moreover, some design guidelines will be provided to tailor the characteristics of the fiber. Finally, it will be discussed how these fibers can be used to increase the TMI threshold of fiber laser systems.
C. Stihler, C. Jauregui, S. Kholaif, and J. Limpert
The sensitivity of the mode instability threshold to different types of intensity noise
Proc. SPIE, 11260 :1126018 (February 2020)
Abstract:
In this work we experimentally and theoretically investigate the impact of seed intensity-noise on the threshold of transverse mode instability (TMI) in Yb-doped, high-power fiber laser systems and compare it to the impact of pump intensity-noise. Former studies have shown that pump intensity-noise significantly decreases the TMI threshold due to the introduction of a phase shift between the modal interference pattern and the thermallyinduced refractive index grating in the fiber. However, it can be expected that fluctuations of the seed power will also induce such phase shifts due to a change of the extracted energy and the heat load in the fiber. Thus, it is important to investigate which one, i.e. the seed-or the pump intensity-noise, has a severer impact on the TMI threshold. Our experiments have shown that the TMI threshold of a fiber amplifier was decreased by increasing the seednoise amplitude. However, contrary to conventional belief, the impact of seed intensity-noise was much weaker than the one of pump intensity-noise. The measurements are in good agreement with our simulations and can be well explained with previous studies about the noise transfer function. The reason for the weaker impact of seed intensity-noise on the TMI threshold is the attenuation of its frequency components below 20 kHz in saturated fiber amplifiers, which includes the frequencies relevant for TMI. Thus, the main trigger for TMI in saturated fiber amplifiers can be considered to be pump intensity-noise. A suppression of this noise below 20 kHz represents a promising way to increase the TMI threshold of fiber laser systems.
T. Heuermann, M. Gebhardt, Z. Wang, C. Gaida, F. Maes, C. Jauregui, and J. Limpert
Watt-class optical parametric amplification driven by a thulium doped fiber laser in the molecular fingerprint region
Proc. SPIE, 11260 :112600I (February 2020)
Abstract:
Numerous molecules important for environmental and life sciences feature strong absorption bands in the molecular fingerprint region from 3 μm-20 μm. While mature drivers at 1 μm wavelength are the workhorse for the generation of radiation up to 5 μm (utilizing down-conversion in nonlinear crystals) they struggle to directly produce radiation beyond this limit, due to impeding nonlinear absorption in non-oxide crystals. Since only non-oxide crystals provide transmission in the whole molecular fingerprint region, a shift to longer driving wavelengths is necessary for a power scalable direct conversion of radiation into the wavelength region beyond 5 μm. In this contribution, we present a high-power single-stage optical parametric amplifier driven by a state of the art 2 μm wavelength, thulium-doped fiber chirped pulse amplifier. In this experiment, the laser system provided 23 W at 417 kHz repetition rate with 270 fs pulse duration to the parametric amplifier. The seed signal is produced by supercontinuum generation in 3 mm of sapphire and pre-chirped with 3 mm of germanium. Combining this signal with the pump radiation and focusing it into a 2 mm thick GaSe crystal with a pump intensity of 160 GW/cm2 lead to an average idler power of 700 mW with a spectrum spanning from 9 μm-12 μm. To the best of our knowledge, this is the highest average power reported from a parametric amplifier directly driven by a 2 μm ultrafast laser in the wavelength region beyond 5 μm. Employing common multi-stage designs, this approach might in the future enable multi-watt high-power parametric amplification in the long wavelength mid infrared.
M. Müller, C. Aleshire, L. Stark, J. Buldt, A. Steinkopff, E. Haddad, F. Légaré, A. Klenke, A. Tünnermann, and J. Limpert
10.4 kW 12-channel ultrafast fibre laser
Advanced Solid State Lasers ( 2020)
DOI
J. Fellinger, A. Mayer, W. Grosinger, G. Winkler, L. Perner, S. Droste, S. Salman, C. Li, C. Heyl, and I. Hartl
Flexible Figure-9 Yb: Fiber Laser: Operation Regimes and Noise Performance
Advanced Solid State Lasers ( 2020)
DOI
S. Hädrich, N. Walther, E. Shestaev, T. Nagy, P. Simon, A. Blumenstein, R. Klas, J. Buldt, H. Stark, S. Breitkopf, and . others
High Pulse Energy CEP-stable Few-cycle Pulses at High Average Power: Status of the ELI-ALPS HR2 System
High Intensity Lasers and High Field Phenomena ( 2020)
DOI
M. Gebhardt, T. Heuermann, C. Gaida, Z. Wang, M. Lenski, R. Klas, A. Kirsche, C. Liu, S. Hädrich, C. Jauregui, and . others
High-order harmonic generation in noble gas driven by high-power ultrafast thulium-doped fiber lasers
Advanced Solid State Lasers ( 2020)
DOI
P. Balla, A. B. Wahid, I. Sytcevich, C. Guo, A.-L. Viotti, l. Silletti, A. Cartella, S. Ališauskas, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, B. Manschwetus, T. Lang, A. Trabattoni, F. Calegari, A. Couairon, A. L'Huillier, C. L. Arnold, I. Hartl, and C. M. Heyl
Post-compression of picosecond pulses to four optical cycles
OSA High-brightness Sources and Light-driven Interactions Congress 2020 (EUVXRAY, HILAS, MICS) ( 2020)
DOI
P. Balla, A. B. Wahid, I. Sytcevich, C. Guo, A.-L. Viotti, l. Silletti, A. Cartella, S. Ališauskas, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, B. Manschwetus, T. Lang, A. Trabattoni, F. Calegari, A. Couairon, A. L'Huillier, C. L. Arnold, I. Hartl, and C. M. Heyl
Post-Compression of Picosecond Pulses to Four Optical Cycles via Multi-Pass Spectral Broadening
The 22nd International Conference on Ultrafast Phenomena 2020 ( 2020)
DOI
R. Klas, W. Eschen, A. Kirsche, J. Rothhardt, and J. Limpert
Power scalable fiber laser driven high-harmonic source for broadband high photon flux continua
Compact EUV & X-ray Light Sources ( 2020)
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