Johannes Weitenberg
RWTH Aachen University
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Publication
Featured researches published by Johannes Weitenberg.
Optics Letters | 2010
Peter Russbueldt; Torsten Mans; Johannes Weitenberg; Hans-Dieter Hoffmann; Reinhart Poprawe
We demonstrate a compact diode-pumped Yb:KGW femtosecond oscillator-Yb:YAG Innoslab amplifier master oscillator power amplifier (MOPA) with nearly transform-limited 636 fs pulses at 620 W average output power, 20 MHz repetition rate, and beam quality of M(x)(2) = 1.43 and M(y)(2) = 1.35. By cascading two amplifiers, we attain an average output power of 1.1 kW, a peak power of 80 MW, and a 615 fs pulse width in a single linearly polarized beam. The power-scalable MOPA is operated at room temperature, and no chirped-pulse amplification technique is used.
Optics Express | 2009
Peter Russbueldt; T. Mans; G. Rotarius; Johannes Weitenberg; H.D. Hoffmann; Reinhart Poprawe
The Innoslab design, already established for neodymium doped laser crystals, was applied to ytterbium doped laser materials. Recent progresses in brightness of high power diode lasers facilitate efficient pumping of quasi-three-level laser materials. Innoslab amplifiers are compared to competing thin-disk and fiber fs-amplifiers. A compact diode-pumped Yb:YAG Innoslab fs-oscillator-amplifier system, scalable to the kilowatt range, was realized. Numerical simulations result in conditions for high efficiency and beam quality. Nearly transform and diffraction limited 680 fs pulses at 400 W average output power and 76 MHz repetition rate without using CPA technology have been achieved at room temperature so far.
Optics Letters | 2011
Andreas Vernaleken; Johannes Weitenberg; Thomas Sartorius; Peter Russbueldt; Waldemar Schneider; Sarah L. Stebbings; Matthias F. Kling; Peter Hommelhoff; Hans-Dieter Hoffmann; Reinhart Poprawe; Ferenc Krausz; T. W. Hänsch; Thomas Udem
We report on single-pass high-harmonic generation (HHG) with amplified driving laser pulses at a repetition rate of 20.8 MHz. An Yb:YAG Innoslab amplifier system provides 35 fs pulses with 20 W average power at 1030 nm after external pulse compression. Following tight focusing into a xenon gas jet, we observe the generation of high-harmonic radiation of up to the seventeenth order. Our results show that state-of-the-art amplifier systems have become a promising alternative to cavity-assisted HHG for applications that require high repetition rates, such as frequency comb spectroscopy in the extreme UV.
Optics Letters | 2014
Henning Carstens; Nikolai Lilienfein; Simon Holzberger; Christoph Jocher; Tino Eidam; Jens Limpert; Andreas Tünnermann; Johannes Weitenberg; Dylan C. Yost; A. Alghamdi; Z.A. Alahmed; Abdallah M. Azzeer; Alexander Apolonski; Ernst E. Fill; Ferenc Krausz; Ioachim Pupeza
We investigate power scaling of ultrashort-pulse enhancement cavities. We propose a model for the sensitivity of a cavity design to thermal deformations of the mirrors due to the high circulating powers. Using this model and optimized cavity mirrors, we demonstrate 400 kW of average power with 250 fs pulses and 670 kW with 10 ps pulses at a central wavelength of 1040 nm and a repetition rate of 250 MHz. These results represent an average power improvement of one order of magnitude compared to state-of-the-art systems with similar pulse durations and will thus benefit numerous applications such as the further scaling of tabletop sources of hard x rays (via Thomson scattering of relativistic electrons) and of soft x rays (via high harmonic generation).
Optics Express | 2013
Henning Carstens; Simon Holzberger; Jan Kaster; Johannes Weitenberg; V. Pervak; Alexander Apolonskiy; Ernst E. Fill; Ferenc Krausz; Ioachim Pupeza
In passive enhancement cavities the achievable power level is limited by mirror damage. Here, we address the design of robust optical resonators with large spot sizes on all mirrors, a measure that promises to mitigate this limitation by decreasing both the intensity and the thermal gradient on the mirror surfaces. We introduce a misalignment sensitivity metric to evaluate the robustness of resonator designs. We identify the standard bow-tie resonator operated close to the inner stability edge as the most robust large-mode cavity and implement this cavity with two spherical mirrors with 600 mm radius of curvature, two plane mirrors and a round trip length of 1.2 m, demonstrating a stable power enhancement of near-infrared laser light by a factor of 2000. Beam radii of 5.7 mm × 2.6 mm (sagittal × tangential 1/e(2) intensity radius) on all mirrors are obtained. We propose a simple all-reflective ellipticity compensation scheme. This will enable a significant increase of the attainable power and intensity levels in enhancement cavities.
Optics Express | 2011
Johannes Weitenberg; Peter Rußbüldt; Tino Eidam; Ioachim Pupeza
We demonstrate a high-finesse femtosecond enhancement cavity with an on-axis obstacle. By inserting a wire with a width of 5% of the fundamental mode diameter, the finesse of F = 3400 is only slightly reduced to F = 3000. The low loss is due to the degeneracy of transverse modes, which allows for exciting a circulating field distribution avoiding the obstacle. We call this condition quasi-imaging. The concept could be used for output coupling of intracavity-generated higher-order harmonics through an on-axis opening in one of the cavity mirrors.
Optics Express | 2013
Dominik Esser; Johannes Weitenberg; Wiebke Broering; Ioachim Pupeza; Simon Holzberger; Hans-Dieter Hoffmann
We demonstrate micro structuring of fused-silica laser mirror substrates by Inverse Laser Drilling. Slits of a width down to ~80 µm and circular holes with diameters down to ~50 µm have been structured into quarter-inch thick substrates. Except for chipping, the surface areas around these openings have not been irreversibly affected by the manufacturing process. The micro structured mirrors can be used for geometrical output coupling of coherent EUV radiation from cavity-enhanced high harmonic generation.
Journal of Optics | 2015
Johannes Weitenberg; P. Rußbüldt; Ioachim Pupeza; Th. Udem; H-D Hoffmann; R Poprawe
We describe a novel method for providing geometrical on-axis access to an optical enhancement resonator through an on-axis aperture at one of its mirrors. A superposition of transverse modes in a stable degenerate resonator is used to form a field distribution which avoids the aperture and therefore exhibits small loss. Upon propagation in the resonator the modes acquire a different phase, and an on-axis intensity maximum is formed at a different position. We call this a quasi-imaging resonator, because it is related to imaging in the sense that a hole in the field distribution, exacted by the aperture, is reproduced after a resonator round trip.
conference on lasers and electro-optics | 2011
Ioachim Pupeza; Johannes Weitenberg; Peter Rußbüldt; Tino Eidam; Jens Limpert; Ernst E. Fill; Thomas Udem; Hans-Dieter Hoffmann; Reinhart Poprawe; Andreas Tünnermann; Ferenc Krausz
Degenerate transverse modes are used to excite a field distribution with maximum on axis intensity near the focus and avoiding a large on-axis aperture far away from the focus in a femtosecond resonator with finesse 3000.
conference on lasers and electro-optics | 2011
Ioachim Pupeza; Jan Kaster; Tino Eidam; Birgitta Bernhardt; Johannes Weitenberg; Ronald Holzwarth; T. W. Hänsch; Thomas Udem; Jens Limpert; Andreas Tünnermann; Ernst E. Fill; Ferenc Krausz
A resonator is presented, designed to overcome current power and intensity scaling limitations of HHG enhancement cavities and offering the prospect of MW circulating powers for ultrashort pulses. Suitable XUV output coupling mechanisms are addressed.