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Andreas Tünnermann

Bio: Andreas Tünnermann is an academic researcher from Fraunhofer Society. The author has contributed to research in topics: Fiber laser & Laser. The author has an hindex of 97, co-authored 1738 publications receiving 43757 citations. Previous affiliations of Andreas Tünnermann include Schiller International University & University of Jena.


Papers
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Journal ArticleDOI
TL;DR: Theoretical models and qualitative explanations of experimental results are presented in this paper for femtosecond laser ablation of solid targets by 0.2-5000 ps Ti: Sapphire laser pulses.
Abstract: Laser ablation of solid targets by 0.2–5000 ps Ti: Sapphire laser pulses is studied. Theoretical models and qualitative explanations of experimental results are presented. Advantages of femtosecond lasers for precise material processing are discussed and demonstrated.

2,513 citations

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TL;DR: In this paper, the authors studied the ablation of metal targets by Ti:sapphire laser radiation and showed that the intensity depends logarithmically on the laser fluence.
Abstract: Ablation of metal targets by Ti:sapphire laser radiation is studied. The ablation depth per pulse is measured for laser pulse durations between 150 fs and 30 ps and fluences ranging from the ablation threshold ∼0.1 J/cm2 up to 10 J/cm2. Two different ablation regimes are observed for the first time. In both cases the ablation depth per pulse depends logarithmically on the laser fluence. A simple theoretical model for a qualitative description of the experimental results is presented.

914 citations

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TL;DR: An overview of the state of the art in the field can be found in this paper, where the authors discuss present challenges and the future outlook of high-power fiber laser applications.
Abstract: High-power fibre lasers are in demand for industrial, defence and scientific applications. This review provides an overview of the present state of the art in the field and discusses present challenges and the future outlook.

781 citations

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TL;DR: A three-dimensional chiral optical metamaterial is experimentally demonstrated that exhibits an asymmetric transmission for forwardly and backwardly propagating linearly polarized light.
Abstract: We experimentally demonstrate a three-dimensional chiral optical metamaterial that exhibits an asymmetric transmission for forwardly and backwardly propagating linearly polarized light. The observation of this novel effect requires a metamaterial composed of three-dimensional chiral meta-atoms without any rotational symmetry. Our analysis is supported by a systematic investigation of the transmission matrices for arbitrarily complex, generally lossy media that allows deriving a simple criterion for asymmetric transmission in an arbitrary polarization base. Contrary to physical intuition, in general the polarization eigenstates in such three-dimensional and low-symmetry metamaterials do not obey fixed relations and the associated transmission matrices cannot be symmetrized.

577 citations

Journal ArticleDOI
TL;DR: This Letter reports on the generation of 830 W compressed average power from a femtosecond fiber chirped pulse amplification (CPA) system and discusses further a scaling potential toward and beyond the kilowatt level by overcoming the current scaling limitations imposed by the transversal spatial hole burning.
Abstract: In this Letter we report on the generation of 830 W compressed average power from a femtosecond fiber chirped pulse amplification (CPA) system In the high-power operation we achieved a compressor throughput of about 90% by using high-efficiency dielectric gratings The output pulse duration of 640 fs at 78 MHz repetition rate results in a peak power of 12 MW Additionally, we discuss further a scaling potential toward and beyond the kilowatt level by overcoming the current scaling limitations imposed by the transversal spatial hole burning

559 citations


Cited by
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08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam.
Abstract: Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

4,613 citations

Journal ArticleDOI
TL;DR: The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices.
Abstract: Since its discovery, the asymmetric Fano resonance has been a characteristic feature of interacting quantum systems. The shape of this resonance is distinctively different from that of conventional symmetric resonance curves. Recently, the Fano resonance has been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials. The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices.

3,536 citations

Journal ArticleDOI
04 Oct 2006
TL;DR: In this paper, a review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime.
Abstract: A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

3,361 citations

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TL;DR: Topological photonics is a rapidly emerging field of research in which geometrical and topological ideas are exploited to design and control the behavior of light as mentioned in this paper, which holds great promise for applications.
Abstract: Topological photonics is a rapidly emerging field of research in which geometrical and topological ideas are exploited to design and control the behavior of light. Drawing inspiration from the discovery of the quantum Hall effects and topological insulators in condensed matter, recent advances have shown how to engineer analogous effects also for photons, leading to remarkable phenomena such as the robust unidirectional propagation of light, which hold great promise for applications. Thanks to the flexibility and diversity of photonics systems, this field is also opening up new opportunities to realize exotic topological models and to probe and exploit topological effects in new ways. This article reviews experimental and theoretical developments in topological photonics across a wide range of experimental platforms, including photonic crystals, waveguides, metamaterials, cavities, optomechanics, silicon photonics, and circuit QED. A discussion of how changing the dimensionality and symmetries of photonics systems has allowed for the realization of different topological phases is offered, and progress in understanding the interplay of topology with non-Hermitian effects, such as dissipation, is reviewed. As an exciting perspective, topological photonics can be combined with optical nonlinearities, leading toward new collective phenomena and novel strongly correlated states of light, such as an analog of the fractional quantum Hall effect.

3,052 citations