Publications

2019

show Content M. Heck, G. Schwartz, R. G. Krämer, D. Richter, T. A. Goebel, C. Matzdorf, A. Tünnermann and S. Nolte, "Control of higher-order cladding mode excitation with tailored femtosecond-written long period fiber gratings," Opt. Express 27, 4292 (2019).

Abstract

We report on the detailed investigation of the core to cladding mode coupling in femtosecond-written long period fiber gratings (LPFG). It is shown that the excitation of higher-order cladding modes with strong selectivity and high precision is possible. The coupling behavior of several gratings, as well as its dependence on the modified core cross-section, is determined theoretically and confirmed experimentally by its spectral response. The presented tool paves the way for a completely new class of tailored LPFGs for different fiber integrated devices.

doi: 10.1364/OE.27.004292

show Content H. Kämmer, G. Matthäus, K. A. Lammers, C. Vetter, M. Chambonneau, and S. Nolte, "Origin of Waveguiding in Ultrashort Pulse Structured Silicon," Laser Photonics Rev. 13, 1800268 (2019).

Abstract

The origin of waveguiding in the bulk of silicon after sub‐ps laser inscription is investigated. Locally resolved Raman measurements of waveguide cross sections and along the propagation axis reveal highly localized crystal deformations. These modifications consist of highly confined regions of silicon with a disturbed crystal structure accompanied with strain. This transformation is responsible for a local increase of the refractive index allowing localized waveguiding. On the basis of near‐field measurements at an excitation wavelength of 1550 nm, the absolute value of the refractive index change is estimated to be in the range of 10−3. The origin of waveguiding after sub‐picosecond laser inscription in the bulk of crystalline silicon is examined. Micro‐Raman spectroscopy analyses of the waveguide cross sections reveal highly localized disturbed crystal structures. These material transformations result in a local increase of the refractive index responsible for guiding light.

doi: 10.1002/lpor.201800268

show Content C. P. Jisha, J. Beeckman, F. Van Acker, K. Neyts, S. Nolte and A. Alberucci, "Generation of multiple solitons using competing nonlocal nonlinearities," Opt. Lett. 44, 1162 (2019).

Abstract

We discuss the dynamics of fundamental Gaussian beams launched in saturable and nonlocal nonlinear media. Solely in the presence of a self-focusing saturable nonlinearity, the breathing solitons undergo strong deformation. The addition of a defocusing nonlinearity leads to the generation of couples of solitons. Experimentally, we demonstrate in nematic liquid crystals the formation of multiple spatial solitons starting from a bell-shaped input, with both direction and the number of filaments depending on the input power, confirming the theoretical predictions.

doi: 10.1364/OL.44.001162

show Content R. G. Krämer et al., "Femtosecond written fiber Bragg gratings in Ytterbium-doped fibers for fiber lasers in the kilowatt regime," Opt. Lett. 44, 723-726 (2019).

Abstract

We investigate the high-power durability of fiber Bragg gratings written directly into an ytterbium-doped large mode area fiber using ultrashort laser pulses. The gratings were successfully integrated as a high reflector into an oscillator setup reaching up to 1.9 kW signal output power with an efficiency of 87%. Defect states induced during the inscription process could be drastically reduced by a self-annealing process resulting in a stable laser performance.

 doi: 10.1364/OL.44.000723

show Content S. C. Warren-Smith et al., "Tunable multi-wavelength third-harmonic generation using exposed-core microstructured optical fiber," Opt. Lett. 44, 626 (2019)

Abstract

We demonstrate that exposed-core microstructured optical fibers offer multiple degrees of freedom for tailoring third-harmonic generation through the core diameter, input polarization, and nanofilm deposition. Varying these parameters allows control of the phase-matching position between an infrared pump wavelength and the generated visible wavelengths. In this Letter, we show how increasing the core diameter over previous experiments (2.57 μm compared to 1.85 μm) allows the generation of multiple wavelengths, which can be further controlled by rotating the input pump polarization and the deposition of dielectric nanofilms. This can lead to highly tailorable light sources for applications such as spectroscopy or nonlinear microscopy.

doi: 10.1364/OL.44.000626

show Content F. Maes, C. Stihler, L.-P. Pleau, V. Fortin, J. Limpert, M. Bernier, and R. Vallée, "3.42 µm lasing in heavily-erbium-doped fluoride fibers," Opt. Express 27, 2170 (2019).

Abstract

In this paper, we investigate laser emission at 3.4μm in heavily-erbium-doped fluoride fibers using dual-wavelength pumping. To this extent, a monolithic 7 mol% erbium-doped fluoride fiber laser bounded by intracore fiber Bragg gratings at 3.42 μm is used to demonstrate a record efficiency of 38.6 % with respect to the 1976 nm pump. Through numerical modeling, we show that similar laser performances at 3.4 μm can be expected in fluoride fibers with erbium concentrations ranging between 1 – 7 mol%, although power scaling should rely on lightly-doped fibers to mitigate the heat load. Moreover, this work studies transverse mode-beating of the 1976 nm core pump and its role in the generation of a periodic luminescent grating and in the trapping of excitation in the metastable energy levels of the erbium system. Finally, we also report on the bistability of the 3.42 μm output power of the 7 mol% erbium-doped fluoride fiber laser.

doi: 10.1364/OE.27.002170

show Content G. K. Tadesse et al., “Wavelength-scale ptychographic coherent diffractive imaging using a high-order harmonic source”, Sci. Rep. 9(1), 1735 (2019).

Abstract

Ptychography enables coherent diffractive imaging (CDI) of extended samples by raster scanning across the illuminating XUV/X-ray beam thereby generalizing the unique advantages of CDI techniques. Table-top realizations of this method are urgently needed for many applications in sciences and industry. Previously, it was only possible to image features much larger than the illuminating wavelength with table-top ptychography although knife-edge tests suggested sub-wavelength resolution. However, most real-world imaging applications require resolving of the smallest and closely-spaced features of a sample in an extended field of view. In this work, we resolve features as small as 2.5 \lambda (45 nm) by using a table-top ptychography setup and a high-order harmonic XUV source. For the first time, a Rayleigh-type criterion is used as a direct and unambiguous resolution metric for high-resolution table-top setup. This reliably qualifies this imaging system for real-world applications e.g. in biological sciences, material sciences, imaging integrated circuits and semiconductor mask inspection.

doi:10.1017/S1431927618012515

show Content 3. Maximilian Heck, Ria G. Krämer, Tobias Ullsperger, Thorsten A. Goebel, Daniel Richter, Andreas Tünnermann, and Stefan Nolte, "Efficient long period fiber gratings inscribed with femtosecond pulses and an amplitude mask," Opt. Lett. 44, 3980-3983 (2019)

Abstract

We present efficient long period fiber gratings written with femtosecond laser pulses at 800 nm and an amplitude mask, to the best of our knowledge, for the first time. The measured transmission spectra depict strong resonances, while the total grating length and polarization-dependent loss could be significantly reduced compared to previous results. Two gratings are exemplarily shown—one in a standard single mode, and one in a large-mode-area fiber revealing a predictable spectrum without intermediate peaks due to the suppression of coupling to asymmetric higher-order cladding modes.

doi: 10.1364/OL.44.003980

show Content 2. C. P. Jisha, A. Alberucci, J. Beeckman and S. Nolte, "Nonlinear localization of light using Pancharatnam-Berry phase". OPN Year in Review, December (2019)

Abstract

Since its introduction by Sir Michael Berry in 1984, geometric phase became of fundamental importance in physics, with applications ranging from solid state physics to optics. In optics, Pancharatnam-Berry phase allows the tailoring of optical beams by a local control of their polarization. Here we discuss light propagation in the presence of an intensity-dependent local modulation of the Pancharatnam-Berry phase. The corresponding self-modulation of the wavefront counteracts the natural spreading due to diffraction, i.e., self-focusing takes place. No refractive index variation is associated with the self-focusing: the confinement is uniquely due to a nonlinear spin-orbit interaction. The phenomenon is investigated, both theoretically and experimentally, considering the reorientational nonlinearity in liquid crystals, where light is able to rotate the local optical axis through an intensity-dependent optical torque. Our discoveries pave the way to the investigation of a new family of nonlinear waves featuring a strong interaction between the spin and the orbital degrees of freedom.

doi: 10.1103/PhysRevX.9.021051

show Content 1. F. Löchner, R. Mupparapu, M. Steinert, A. George, Z. Tang, A. Turchanin, T. Pertsch, I. Staude, and F. Setzpfandt, “Controlling second-harmonic diffraction by nano-patterning MoS2 monolayers” accepted at Opt. Express (2019)

Abstract

The ability to design and enhance the nonlinear optical responses in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) is both of fundamental interest and highly desirable for developing TMDC-based nonlinear optical applications, such as nonlinear convertors and optical modulators. Here, we report for the first time a strong anisotropic enhancement of optical second-harmonic generation (SHG) in monolayer molybdenum disulfide (MoS2) by integrating with one-dimensional (1D) titanium dioxide nanowires (NWs). The SHG signal from the MoS2/NW hybrid structures is over 2 orders of magnitude stronger than that in the bare monolayer MoS2. Polarized SHG measurements revealed a giant anisotropy in SHG response of the MoS2/NW hybrid. The pattern of the anisotropic SHG depends highly on the stacking angle between the nanowire direction and the MoS2 crystal orientation, which is attributed to the 1D NW-induced directional strain fields in the layered MoS2. A similar effect has also been observed in bilayer MoS2/NW hybrid structure, further proving the proposed scenario. This work provides an effective approach to selectively and directionally designing the nonlinear optical response of layered TMDCs, paving the way for developing high-performance, anisotropic nonlinear photonic nanodevices.

doi: 10.1021/acs.nanolett.9b01933

show Content A. Alberucci, C. P. Jisha, U. Peschel and S. Nolte, Effective breaking of the actionreaction principle using spatial solitons, Phys. Rev. A 100, 011802(R) (2019).

Abstract

We discuss a class of interactions between self-confined optical beams breaking the action-reaction principle. The effective force intertwining the beams does not satisfy momentum conservation, paving the way to the potential existence of situations where both beams are pushed in the same direction, in turn leading to the so-called diametric drive. In our theoretical proposal the interaction between the two light beams is enabled by optical nonlinearity. The nonlinearity is assumed to change sign with the light polarization, in turn allowing the two light beams to be attracted or repelled by an inhomogeneous region according to the photon polarization. We demonstrate that this exotic type of nonlinear spin-orbit-like interaction can be achieved in nematic liquid crystals (NLCs). In fact, depending on the input polarization, in NLCs a change in temperature corresponds to a focusing or defocusing index change. For the polarization seeing a thermal defocusing response (corresponding to the extraordinary component), the self-confinement is ensured by the simultaneous action of reorientational nonlinearity.

doi: 10.1103/PhysRevA.100.011802

show Content M. Heck, J.-C. Gauthier, A. Tünnermann, R. Vallée, S. Nolte and M. Bernier, “Long period fiber gratings for the mitigation of parasitic laser effects in mid-infrared fiber amplifiers,” Opt. Express 27, 21347-21357 (2019).

Abstract

A concept to mitigate parasitic lasing in mid-IR fiber amplifiers using a single long period fiber grating is shown. Using tightly confined ultrashort laser pulses at 800 nm, a grating was directly inscribed into the core of an erbium doped fluoride glass fiber showing a strong attenuation down to −27 dB at desired wavelength. The concept reveals great potential to improve the average output power and attainable spectral range of low repetition rate in-amplifier supercontinuum generation.

doi: 10.1364/OE.27.021347

show Content A. L. M. Muniz, M. Wimmer, A. Bisianov, R. Morandotti, U. Peschel, “Collapse on the line – how synthetic dimensions influence nonlinear effects,” Scientific Reports 9, 9518 (2019).

Abstract

Power induced wave collapse is one of the most fascinating phenomena in optics as it provides extremely high intensities, thus stimulating a range of nonlinear processes. For low power levels, propagation of beams in bulk media is dominated by diffraction, while above a certain threshold self-focusing is steadily enhanced by the action of a positive nonlinearity. An autocatalytic blow-up occurs, which is only stopped by saturation of the nonlinearity, material damage or the inherent medium discreteness. In the latter case, this leads to energy localization on a single site. It is commonly believed that for cubic nonlinearities, this intriguing effect requires at least two transverse dimensions to occur and is thus out of reach in fiber optics. Following the concept of synthetic dimensions, we demonstrate that mixing short and long-range interaction resembles a two-dimensional mesh lattice and features wave collapse at mW-power levels in a genuine 1D system formed by coupled fiber loops.

doi: 10.1038/s41598-019-46060-8.

show Content K. Lammers, M. Ehrhardt, T. Malendevych, X. Xu, C. Vetter, A. Alberucci, A. Szameit and S. Nolte, Embedded nanogratings-based waveplates for polarization control in integrated photonic circuits, Opt. Mat. Express 9, 2560-2572 (2019).

Abstract

Femtosecond laser direct writing (FLDW) enables precise three-dimensional structuring of transparent host materials such as fused silica. With this technique, reliable integrated optical circuits can be written, which are also a possible candidate for future quantum technologies. We demonstrate the manufacturing of integrated waveplates with arbitrary orientations and various phase delays by combining embedded birefringent nanograting structures and FLDW waveguides in fused silica glass. These waveplates can be used both for classical applications and for quantum gates.

doi: 10.1364/OME.9.002560

show Content Aaron Reupert, Maximilian Heck, Stefan Nolte, and Lothar Wondraczek, "Side-emission properties of femtosecond laser induced scattering centers in optical fibers," Opt. Mater. Express 9, 2497-2510 (2019)

Abstract

Fiber optical light diffusers that enable interstitial light delivery have become a useful tool for various illumination tasks, such as in photodynamic therapy. However, existing methods based on light diffusing fiber tips are not applicable for spatially selective light delivery in more complex structures. Here, we employ femtosecond laser induced scattering centers without mechanical manipulation and removal of the outer coatings for generating customized emission patterns. Tailoring of the cumulative emission profile is achieved through controlling the step-width between modification spots. An in-depth evaluation shows that the side-emission pattern is the result of an interplay of several scattering mechanisms that interact with cladding and core modes.

doi: 10.1364/OME.9.002497

show Content Kay Schaarschmidt, Hongwen Xuan, Jens Kobelke, Mario Chemnitz, Ingmar Hartl, and Markus A. Schmidt, "Long-term stable supercontinuum generation and watt-level transmission in liquid-core optical fibers," Opt. Lett. 44, 2236-2239 (2019)

Abstract

Due to their unique properties such as transparency, tunability, nonlinearity, and dispersion flexibility, liquid-core fibers represent an important approach for future coherent mid-infrared light sources. However, the damage thresholds of these fibers are largely unexplored. Here we report on the generation of soliton-based supercontinua in carbon disulfide (CS2) liquid-core fibers at average power levels as high as 0.5 W operating stably for a long term (>70h) without any kind of degradation or damage. Additionally, we also show stable high-power pulse transmission through liquid-core fibers exceeding 1 W of output average power for both CS2 and tetrachloroethylene as core materials.

doi: 10.1364/OL.44.002236

show Content Schaarschmidt, Hongwen Xuan, Jens Kobelke, Mario Chemnitz, Ingmar Hartl, and Markus A. Schmidt, "Long-term stable supercontinuum generation and watt-level transmission in liquid-core optical fibers," Opt. Lett. 44, 2236-2239 (2019)

Abstract

Due to their unique properties such as transparency, tunability, nonlinearity, and dispersion flexibility, liquid-core fibers represent an important approach for future coherent mid-infrared light sources. However, the damage thresholds of these fibers are largely unexplored. Here we report on the generation of soliton-based supercontinua in carbon disulfide (CS2) liquid-core fibers at average power levels as high as 0.5 W operating stably for a long term (>70h) without any kind of degradation or damage. Additionally, we also show stable high-power pulse transmission through liquid-core fibers exceeding 1 W of output average power for both CS2 and tetrachloroethylene as core materials.

doi: 10.1364/OL.44.002236

2018

show Content M. Nissen, B. Doherty, J. Hamperl, J. Kobelke, K. Weber, T. Henkel, M. A. Schmidt, "UV Absorption Spectroscopy in Water-Filled Antiresonant Hollow Core Fibers for Pharmaceutical Detection," Sensors 18, 478-480 (2018)

Abstract

Due to a worldwide increased use of pharmaceuticals and, in particular, antibiotics, a growing number of these substance residues now contaminate natural water resources and drinking supplies. This triggers a considerable demand for low-cost, high-sensitivity methods for monitoring water quality. Since many biological substances exhibit strong and characteristic absorption features at wavelengths shorter than 300 nm, UV spectroscopy presents a suitable approach for the quantitative identification of such water-contaminating species. However, current UV spectroscopic devices often show limited light-matter interaction lengths, demand sophisticated and bulky experimental infrastructure which is not compatible with microfluidics, and leave large fractions of the sample analyte unused. Here, we introduce the concept of UV spectroscopy in liquid-filled anti-resonant hollow core fibers, with large core diameters and lengths of approximately 1 m, as a means to overcome such limitations. This extended light-matter interaction length principally improves the concentration detection limit by two orders of magnitude while using almost the entire sample volume—that is three orders of magnitude smaller compared to cuvette based approaches. By integrating the fibers into an optofluidic chip environment and operating within the lowest experimentally feasible transmission band, concentrations of the application-relevant pharmaceutical substances, sulfamethoxazole (SMX) and sodium salicylate (SS), were detectable down to 0.1 µM (26 ppb) and 0.4 µM (64 ppb), respectively, with the potential to reach significantly lower detection limits for further device integration.

doi:10.3390/s18020478

show Content M. Chemnitz, R. Scheibinger, Ch. Gaida, M.Gebhardt, F. Stutzki, S. Pumpe, J. Kobelke, A. Tünnermann, J. Limpert, and M. A. Schmidt, "Thermodynamic control of soliton dynamics in liquid-core fibers," Optica 5, 695 (2018).

Abstract

Liquid-core fibers offer local external control over pulse dispersion due to their strong thermodynamic response, offering a new degree of freedom in accurate soliton steering for reconfigurable nonlinear light generation. Here, we show how to accurately control soliton dynamics and supercontinuum generation in carbon disulfide/silica fibers by temperature and pressure tuning, monitored via the spectral location and the onset energy of non-solitonic radiation. Simulations and phase-matching calculations based on an extended thermodynamic dispersion model of carbon disulfide confirm the experimental results, which allows us to demonstrate the potential of temperature detuning of liquid-core fibers for octave spanning recompressible supercontinuum generation in the near-infrared.

doi:10.1364/OPTICA.5.000695

show Content C. Gaida et al., "High-power frequency comb at 2  μm wavelength emitted by a Tm-doped fiber laser system," Opt. Lett. 43, 5178 (2018)

Abstract

We report on the generation of a high-power frequency comb in the 2 μm wavelength regime featuring high amplitude and phase stability with unprecedented laser parameters, combining 60 W of average power with <30  fs<30  fs pulse duration. The key components of the system are a mode-locked Er:fiber laser, a coherence-preserving nonlinear broadening stage, and a high-power Tm-doped fiber chirped-pulse amplifier with subsequent nonlinear self-compression of the pulses. Phase locking of the system resulted in a phase noise of less than 320 mrad measured within the 10 Hz–30 MHz band and 30 mrad in the band from 10 Hz to 1 MHz.

doi:10.1364/OL.43.005178

show Content M. Heck, S. Nolte, A. Tünnermann, R. Vallée, and M. Bernier, "Femtosecond-written long-period gratings in fluoride fibers," Opt. Lett. 43, 1994 (2018).

Abstract

Long-period gratings induced in fluoride glass fibers using femtosecond laser pulses at 800 nm are, to the best of our knowledge, demonstrated for the first time. By means of tightly confined ultrashort laser pulses, smooth periodic lines of refractive index changes are induced along the fiber core. Taking advantage of heat accumulation effects in the focal volume, attenuation peaks down to 24  dB−24  dB , with sharp and predictable spectral resonances, were obtained. Thermal annealing of the grating up to 250°C yielded a significant reduction of the induced refractive index change. The gratings could find applications in various integrated mid-infrared optical devices, such as optical notch filters in fiber amplifiers.

doi:10.1364/OL.43.001994

show Content A. Alberucci, C. P. Jisha, and S. Nolte, "Photonic potential for TM waves," Opt. Lett. 43, 4949 (2018).

Abstract

We discuss the effective photonic potential for TM waves in inhomogeneous isotropic media. The model provides an easy and intuitive comprehension of form birefringence, paving the way for a new approach on the design of graded-index optical waveguides on nanometric scales. We investigate the application to nanophotonic devices, including integrated nanoscale wave plates and slot waveguides.

doi:10.1364/OL.43.004949

show Content T. A. Goebel et al., "Realization of aperiodic fiber Bragg gratings with ultrashort laser pulses and the line-by-line technique," Opt. Lett. 43, 3794 (2018).

Abstract

We demonstrate the fabrication of aperiodic fiber Bragg gratings (AFBGs) for their application as filter elements. Direct inscription was performed by focusing ultrashort laser pulses with an oil-immersion objective into the fiber core and utilizing the line-by-line technique for flexible period adaptation. The AFBGs inscribed allow for the suppression of 10 lines in a single grating and are in excellent agreement with simulations based on the specific design. Applications in astronomy for the suppression of hydroxyl emission lines are discussed.

doi:10.1364/OL.43.003794

show Content K. Bergner, B. Seyfarth, K. A. Lammers, T. Ullsperger, S. Döring, M. Heinrich, M. Kumkar, D. Flamm, A. Tünnermann, and S. Nolte, "Spatio-temporal analysis of glass volume processing using ultrashort laser pulses," Appl. Opt. 57, 4618 (2018).

Abstract

Ultrashort laser pulses allow for the in-volume processing of glass through non-linear absorption, resulting in permanent material changes and the generation of internal stress. Across the manifold potential applications of this technology, process optimization requires a detailed understanding of the laser–matter interaction. Of particular relevance are the deposition of energy inside the material and the subsequent relaxation processes. In this paper, we investigate the spatio-temporal evolution of free carriers, energy transfer, and the resulting permanent modifications in the volume of glass during and after exposure to femtosecond and picosecond pulses. For this purpose, we employ time-resolved microscopy in order to obtain shadowgraphic and interferometric images that allow relating the transient distributions to the refractive index change profile. Whereas the plasma generation time is given by the pulse duration, the thermal dynamics occur over several microseconds. Among the most notable features is the emergence of a pressure wave due to the sudden increase of temperature and pressure within the interaction volume. We show how the structure of the modifications, including material disruptions as well as local defects, can be directly influenced by a judicious choice of pulse duration, pulse energy, and focus geometry.

doi:10.1364/AO.57.004618

show Content G. Matthäus, H. Kämmer, K. A. Lammers, C. Vetter, W. Watanabe, and S. Nolte, "Inscription of silicon waveguides using picosecond pulses," Opt. Express 26, 24089 (2018).

Abstract

Direct writing of single-mode waveguides into crystalline silicon using ps laser pulses is presented. The embedded structures were fabricated by moving the focal position along the beam axis with the help of a long distance microscope objective. In situ monitoring during inscription was performed to analyze the processing dynamics. The waveguide generation is based on pronounced multi-pulse interaction at moderate pulse energies around 100 nJ. All samples were characterized in terms of mode field distribution and damping losses. Calculations indicate an induced refractive index change in the range of 10−3 to 10−2. Moreover, a Y-splitter was realized to demonstrate the potential of this process.

doi:10.1364/OE.26.024089

show Content J. F. Löchner et al., "Polarization-Dependent Second Harmonic Diffraction from Resonant GaAs Metasurfaces," ACS Photonics, 5, 1786 (2018).

Abstract

Resonant semiconductor metasurfaces are an emerging versatile platform for nonlinear photonics. In this work, we investigate second-harmonic generation from metasurfaces consisting of two-dimensional square arrays of gallium arsenide nanocylinders as a function of the polarization of the fundamental wave. To this end, we perform nonlinear second harmonic microscopy, where the pump wavelength is tuned to the resonances of the metasurfaces. Furthermore, imaging the generated nonlinear signal in Fourier space allows us to analyze the spatial properties of the generated second harmonic. Our experiments reveal that the second harmonic is predominantly emitted into the first diffraction orders of the periodic arrangements, and that its intensity varies with the polarization angle of the fundamental wave. While this can be expected from the structure of the GaAs nonlinear tensor, the characteristics of this variation itself are found to depend on the pump wavelength. Interestingly, we show that the metasurface can reverse the polarization dependence of the second harmonic with respect to an unstructured GaAs wafer. These general observations are confirmed by numerical simulations using a simplified model for the metasurface. Our results provide valuable input for the development of metasurface-based classical and quantum light sources based on parametric processes.

doi:10.1021/acsphotonics.7b01533

show Content A. Alberucci, C. P. Jisha, S. Bolis, J. Beeckman and S. Nolte, "Interplay between multiple scattering and optical nonlinearity in liquid crystals," Opt. Lett. 43, 3461 (2018).

Abstract

We discuss the role played by time-dependent scattering on light propagation in liquid crystals. In the linear regime, the effects of the molecular disorder accumulate in propagation, yielding a monotonic decrease in the beam spatial coherence. In the nonlinear case, despite the disorder-imposed Brownian-like motion to the self-guided waves, self-focusing increases the spatial coherence of the beam by inducing spatial localization. Eventually, a strong enhancement in the beam oscillations occurs when power is strong enough to induce self-steering, i.e., in the non-perturbative regime.

doi:10.1364/OL.43.003461

show Content A. Alberucci, R. Barboza, C. P. Jisha, and S. Nolte, "Temporal dynamics of light-written waveguides in unbiased liquid crystals," J. Opt. Soc. Am. B 35, 1878 (2018).

Abstract

The control of light by light is one of the main aims in modern photonics. In this context, a fundamental cornerstone is the realization of light-written waveguides in real time, resulting in all-optical reconfigurability of communication networks. Light-written waveguides are often associated with spatial solitons, that is, non-diffracting waves due to a nonlinear self-focusing effect in the harmonic regime. From an applicative point of view, it is important to establish the temporal dynamics for the formation of such light-written guides. Here, we investigate theoretically the temporal dynamics in nematic liquid crystals, a material where spatial solitons can be induced using continuous wave lasers with a few milliwatts of power. We fully address the role of the spatial walk-off and the longitudinal nonlocality in the waveguide formation. We show that for powers large enough to induce light self-steering the beam undergoes several fluctuations before reaching the stationary regime, in turn leading to a much longer formation time for the light-written waveguide.

doi:10.1364/JOSAB.35.00187

show Content K. Schaarschmidt, S. Weidlich, D. Reul, and M. A. Schmidt, "Bending losses and modal properties of nano-bore optical fibers," Opt. Lett. 43, 4192 (2018).

Abstract

The nano-bore optical fiber geometry represents a new waveguide platform that uniquely allows studying the interaction of low-index fluids and light inside the core of an optical fiber while maintaining total internal reflection as a light guidance mechanism. Here, we have analyzed several application-relevant properties of this novel geometry experimentally and from the simulation perspective, including the analysis of the power fraction inside the bore, the determination of radius-dependent cutoffs, and the identification of single-mode operation domains. The obtained results will pave the way for new application of fiber optics in fields such as optofluidics, nonlinear light generation, and bioanalytics.

doi:10.1364/JOSAB.35.001878

show Content S. Jiang, K. Schaarschmidt, S. Weidlich, and M.A. Schmidt, "Fiber-Integrated Absorption Spectroscopy Using Liquid-Filled Nanobore Optical Fibers," J.Light. Technol. 36, 3970 (2018).

Abstract

Absorption spectroscopy represents one highly relevant approach in current analytics to noninvasively characterize liquid analytes. Here we present the concept of waveguide-integrated absorption spectroscopy via nanobore optical fibers. Using a liquid-filled nanochannel inside the core of a microstructured step-index fiber, the spectroscopic characteristics of liquid analytes located inside the nanochannel are imprinted onto the propagating mode via its evanescent fields, allowing to conduct absorption spectroscopic experiments at extremely small sample volume levels. We reveal the limits of this spectroscopic approach by analyzing the dependence of the power fraction inside the bore on the fiber parameters and experimentally demonstrate its capabilities by (i) using the cut-back technique using an optofluidic mount and (ii) fully encapsulating a highly doped dye solution inside the nanobore fiber. Based on its high degree of integration and the straightforward handling capabilities, application of the nanobore fiber based absorption spectroscopy concept can be anticipated in fields such as bioanalytics, analytical chemistry and environmental science.

doi:10.1109/JLT.2018.2850906

show Content T. Grigorova, R. Sollapur, N. Jayakumar, A. Hoffmann, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, and C. Spielmann, "Measurement of the Dispersion of an Antiresonant Hollow Core Fiber," IEEE Photon. J. 10(4), 1-6 (2018).

Abstract

Due to unique properties, antiresonant hollow core fibers have found widespread use in various fields of science and application. Particular regarding applications that involve ultrashort pulses, precise knowledge of group velocity dispersion is essential to understand the underlying physics and to optimize device performance. Here we report on the successful measurement of the spectral distribution of the group velocity dispersion of the fundamental mode of an antiresonant hollow core fiber in close proximity to and away from a strong strand resonance. The results show the variations of the hundreds of fs 2 /cm near the resonance region, whereas the dispersion is identical to that of a perfect cylindrical waveguide away from the resonance in accordance with a literature. An additional zero dispersion wavelength that is not present in the case of a capillary was experimentally verified. The possibility to tune dispersion via strand resonances opens up a novel pathway towards engineering pulse dispersion, with applications in fields such as nonlinear science and pulse propagation management.

doi:10.1109/JPHOT.2018.2861226

show Content N. Jayakumar, R. Sollapur, A. Hoffmann, T. Grigorova, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, and C. Spielmann, "Polarization evolution in antiresonant hollow core fiber," Appl. Opt. 57, 8529 (2018).

Abstract

We experimentally demonstrate that the ellipticity of light exiting antiresonant hollow core fibers is a function of the input polarization which manifests as ellipticity varying with the azimuthal periodicity of the cornered core.

doi:10.1364/CLEO_SI.2018.SF1K.5

show Content C. Jauregui, C. Stihler, A. Tünnermann, and J. Limpert, "Pump-modulation-induced beam stabilization in high-power fiber laser systems above the mode instability threshold," Opt. Express 26, 10691 (2018)

Abstract

A new way of stabilizing the output beam of a fiber laser system operating above the mode instability threshold is described and the first proof-of-principle experimental results are presented. This technique, which relies on a modulation of the pump power, works by washing the thermally-induced refractive index grating out, which weakens the coupling efficiency between transverse modes. One of the main advantages of this simple, yet powerful, approach is that it can be easily incorporated in already existing fiber laser systems since it does not require any additional optical elements. Using this beam stabilization strategy, a significant pointing stability and beam quality improvement has been demonstrated up to an average power of ~600W, which is a factor of 2 above the mode instability threshold.

doi:10.1364/OE.26.010691

show Content C. Stihler, C. Jauregui, A. Tünnermann, and J. Limpert, "Modal energy transfer by thermally induced refractive index gratings in Yb-doped fibers," Light Sci. Appl. 7, 59 (2018).

Abstract

Thermally induced refractive index gratings in Yb-doped fibers lead to transverse mode instability (TMI) above an average power threshold, which represents a severe problem for many applications. To obtain a deeper understanding of TMI, the evolution of the strength of the thermally induced refractive index grating with the average output power in a fiber amplifier is experimentally investigated for the first time. This investigation is performed by introducing a phase shift between the refractive index grating and modal interference pattern, which is obtained by applying a pump power variation to the fiber amplifier. It is demonstrated that the refractive index grating is sufficiently strong to enable modal energy coupling at powers that are significantly below the TMI threshold if the induced phase shift is sufficiently large. The experiments indicate that at higher powers, the refractive index grating becomes more sensitive to such phase shifts, which will ultimately trigger TMI. Furthermore, the experimental results demonstrate beam cleaning above the TMI threshold via the introduction of a positive phase shift. This finding paves the way for the development of a new class of mitigation strategies for TMI that are based on controlling the phase shift between the thermally induced refractive index grating and modal interference pattern.

doi:10.1038/s41377-018-0061-6

show Content C. Stihler, C. Jauregui, A. Tünnermann, and J. Limpert, "Phase-shift evolution between the modal interference pattern and the thermally-induced refractive index grating in high-power fiber laser systems," Opt. Express 26, 19489 (2018).

Abstract

A phase shift between the modal interference pattern and the thermally-induced refractive index grating is most likely the ultimate trigger for the damaging effect of transverse mode instabilities (TMI) in high-power fiber laser systems. By using comprehensive simulations, the creation and evolution of a thermally-induced phase shift is explained and illustrated in detail. It is shown that such a phase shift can be induced by a variation of the pump power. The gained knowledge about the generation and evolution of the phase shift will allow for the development of new mitigation strategies for TMI.

doi:10.1364/OE.26.019489

show Content M. Chemnitz, C. Gaida, M. Gebhardt, F. Stutzki, J. Kobelke, A. Tünnermann, J. Limpert, and M. A. Schmidt, "Carbon Chloride-core fibers for soliton mediated supercontinuum generation," Opt. Express 26, 3221 (2018).

Abstract

We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl4, C2Cl4). By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 1.92 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (C2Cl4). The measured results match simulations of both the generalized and a hybrid nonlinear Schrödinger equation, with the latter resembling the characteristics of non-instantaneous medium via a static potential term and representing a simulation tool with substantially reduced complexity. We show that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid soliton dynamics.

doi:10.1364/OE.26.003221

show Content T. Heuermann, C. Gaida, M. Gebhardt, and J. Limpert, "Thulium-doped nonlinear fiber amplifier delivering 50  fs pulses at 20  W of average power," Opt. Lett. 43, 4441 (2018).

Abstract

In this Letter, we present an optimized nonlinear amplification scheme in the 2 μm wavelength region. This laser source delivers 50 fs pulses at an 80 MHz repetition rate with exceptional temporal pulse quality and 20 W of average output power. According to predictions from numerical simulations, it is experimentally confirmed that dispersion management is crucial to prevent the growth of side pulses and an increase of the energy content in a temporal pedestal surrounding the self-compressed pulse. Based on these results, we discuss guidelines to ensure high temporal pulse quality from nonlinear femtosecond fiber amplifiers in the anomalous dispersion regime.

doi:10.1364/OL.43.004441

show Content C. Gaida, M. Gebhardt, T. Heuermann, F. Stutzki, C. Jauregui, and J. Limpert, "Ultrafast thulium fiber laser system emitting more than 1  kW of average power," Opt. Lett. 43, 5853 (2018).

Abstract

In this Letter, we report on the generation of 1060 W average power from an ultrafast thulium-doped fiber chirped pulse amplification system. After compression, the pulse energy of 13.2 μJ with a pulse duration of 265 fs at an 80 MHz pulse repetition rate results in a peak power of 50 MW spectrally centered at 1960 nm. Even though the average heat-load in the fiber core is as high as 98 W/m, we confirm the diffraction-limited beam quality of the compressed output. Furthermore, the evolution of the relative intensity noise with increasing average output power has been measured to verify the absence of transversal mode instabilities. This system represents a new average power record for thulium-doped fiber lasers (1150 W uncompressed) and ultrashort pulse fiber lasers with diffraction-limited beam quality, in general, even considering single-channel ytterbium-doped fiber amplifiers.

doi:10.1364/OL.43.005853

show Content T. Lühder, T. Wieduwilt, H. Schneidewind, and M. A. Schmidt, "Electric current-driven spectral tunability of surface plasmon polaritons in gold coated tapered fibers," AIP Adv. 8, 9 (2018).

Abstract

Here we introduce the concept of electrically tuning surface plasmon polaritons using current-driven heat dissipation, allowing controlling plasmonic properties via a straightforward-to-access quantity. The key idea is based on an electrical current flowing through the plasmonic layer, changing plasmon dispersion and phase-matching condition via a temperature-imposed modification of the refractive index of one of the dielectric media involved. This scheme was experimentally demonstrated on the example of an electrically connected plasmonic fiber taper that has sensitivities >50000 nm/RIU. By applying a current, dissipative heat generated inside metal film heats the surrounding liquid, reducing its refractive index correspondingly and thus modifying the phase-matching condition to the fundamental taper mode. We observed spectral shifts of the plasmonic resonance up to 300 nm towards shorter wavelength by an electrical power of ≤ 80 mW, clearly showing that our concept is important for applications that demand precise real-time and external control on plasmonic dispersion and resonance wavelengths.

doi:10.1063/1.5046991

show Content R. Klas, A. Kirsche, M. Tschernajew, J. Rothhardt, and J. Limpert, "Annular beam driven high harmonic generation for high flux coherent XUV and soft X-ray radiation," Opt. Express 26, 19318 (2018).

Abstract

Separation of the high average power driving laser beam from the generated XUV to soft-X-ray radiation poses great challenges in collinear HHG setups due to the losses and the limited power handling capabilities of the typically used separating optics. This paper demonstrates the potential of driving HHG with annular beams, which allow for a straightforward and power scalable separation via a simple pinhole, resulting in a measured driving laser suppression of 5⋅10−3. The approach is characterized by an enormous flexibility as it can be applied to a broad range of input parameters and generated photon energies. Phase matching aspects are analyzed in detail and an HHG conversion efficiency that is only 27% lower than using a Gaussian beam under identical conditions is demonstrated, revealing the viability of the annular beam approach for high flux coherent short-wavelength sources and high average power driving lasers.

doi:10.1364/OE.26.019318

show Content K. Bergner, M. Müller, R. Klas, J. Limpert, S. Nolte, and A. Tünnerman, "Scaling ultrashort laser pulse induced glass modifications for cleaving applications," Appl. Opt. 57, 5941 (2018).

Abstract

Ultrashort laser pulses allow for in-volume processing of glass through non-linear absorption. This results in permanent material changes, largely independent of the processed glass, and it is of particular relevance for cleaving applications. In this paper, a laser with a wavelength of 1030 nm, pulse duration of 19 ps, repetition rate of 10 kHz, and burst regime consisting of either four or eight pulses, with an intra-burst pulse separation of 12.5 ns, is used. Subsequently, a Gaussian–Bessel focal line is generated in a fused silica substrate with the aid of an axicon configuration. We show how the structure of the modifications, including the length of material disruptions and affected zones, can be directly influenced by a reasonable choice of focus geometry, pulse energy, and burst regime. We achieve single-shot modifications with 2 μm in diameter and 7.6 mm in length, exceeding an aspect ratio of 1:3800. Furthermore, a maximum length of 10.8 mm could be achieved with a single shot.

doi:10.1364/AO.57.005941

show Content G. K. Tadesse et al., "High resolution XUV Fourier transform holography on a table top," Sci. Rep. 8, 8677 (2018).

Abstract

Today, coherent imaging techniques provide the highest resolution in the extreme ultraviolet (XUV) and X-ray regions. Fourier transform holography (FTH) is particularly unique, providing robust and straightforward image reconstruction at the same time. Here, we combine two important advances: First, our experiment is based on a table-top light source which is compact, scalable and highly accessible. Second, we demonstrate the highest resolution ever achieved with FTH at any light source (34 nm) by utilizing a high photon flux source and cutting-edge nanofabrication technology. The performance, versatility and reliability of our approach allows imaging of complex wavelength-scale structures, including wave guiding effects within these structures, and resolving embedded nanoscale features, which are invisible for electron microscopes. Our work represents an important step towards real-world applications and a broad use of XUV imaging in many areas of science and technology. Even nanoscale studies of ultra-fast dynamics are within reach.

doi:10.1038/s41598-018-27030-y

show Content M. Wimmer and U. Peschel, "Observation of Time Reversed Light Propagation by an Exchange of Eigenstates," Sci. Rep. 8, 2125 (2018).

Abstract

As time flow dictates all evolution, its effective reversal is a topic of active research in a broad range of disciplines, including acoustics, hydrodynamics and optics. This multifarious set of environments is reflected by a great diversity of approaches to observe various echoes of wave functions. Here, we experimentally demonstrate time reversal of a pulse sequence propagating through a photonic mesh lattice realized by two coupled loops of telecommunication fibres. Our system features a symmetric band structure, which allows for almost perfect reversal of its evolution by exchanging the population between two opposing bands. The protocol applied is based on a non-adiabatic and instantaneous exchange of eigenstates resulting in highly efficient time reversal of a pulse chain.

doi:10.1038/s41598-018-20577-w

show Content Presentations at conferences

Talks

  • Ni. Jayakumar, R. Sollapur, A. Hoffmann, T. Grigorova, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Polarization Evolution in  Antiresonant Hollow-Core Fibers”, Conference on Lasers and Electro-Optics, 2018.

  • Rudrakant Sollapur, Bruno Schmidt, Philippe Lassonde, Shoufei Gao, Yingying Wang, Pu Wang, François Légaré, Christian Spielmann, "2.5 Cycle Pulses Obtained With Self Compression At 1.8 μm In Antiresonant Waveguides ", Conference on Lasers and Electro-Optics, 2018.
  • R. Sollapur, D. Kartashov, M. Zürch, B. E. Schmidt, A. Hoffmann, T.Grigorova, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M Chemnitz, S. Gao, Y. Wang, P. Wang, P. Lassonde, M A. Schmidt, F. Légaré, C. Spielmann / „Supercontinuum and few cycle pulse generation in antiresonant hollow core fibers“: Photonics North, Montreal 2018

  • Vittoria Schuster, Robert Klas, Vinzenz Hilbert, Maxim Tschernajew, Jan Rothhardt, Jens Limpert, Birgitta Bernhard / „Twin Pulse High Harmonic Generation for XUV Fourier Transform Spectroscopy”: Photonics North, Montreal 2018

  • Kim Lammers, Stefan Nolte / „Embedded Nanogratings for Polarization Control in Femtosecond Laser Direct Written Waveguides”: Photonics North, Montreal 2018

  • Maximilian Heck, Réal Vallée, Andreas Tünnermann, Stefan Nolte, Martin Bernier / „Femtosecond-written long period gratings in fluoride fibers”: Photonics North, Montreal 2018

  • Brenda Doherty, Markus A. Schmidt / „Plasmonic nanoparticle-functionalised microstructured optical fibres for biosensing-An optofluidic sensing platform”: Photonics North, Montreal 2018

  • Alessandro Alberucci, Stefan Nolte / „Photonic potential for TM waves”: Photonics North, Montreal 2018

  • Friedrich G. Fröbel, V. Engel, Stefanie Gräfe / „Spin-Dependent Asymmetries in the Photoelectron Momentum Distributions in Single-Photon Double Ionization”: Photonics North, Montreal 2018

Poster

  • Christoph Stihler, Cesar Jauregui , Andreas Tünnermann, Jens Limpert  / „Thermally-induced refractive index gratings enabling modal energy transfer in Yb-doped fibers”: Photonics North, Montreal 2018

  • E. Shestaev, D. Hoff, S. Hädrich, F. Just, T. Eidam, M. Sayler, A. Drozdy, P. Jójárt, A. Szabó, Z. Várallyay, K. Osvay, G.G. Paulus, A. Tünnermann, J. Limpert / „Towards Highly Carrier-Envelope Stable High-Power Few-Cycle Fiber Lasers”: Photonics North, Montreal 2018

  • T. Lühder, T. Wieduwilt, H. Schneidewind, M. A. Schmidt / „Electrically induced tunability  of surface plasmon polaritons in gold coated tapered fibers”: Photonics North, Montreal 2018

  • A.L.M. Muniz, M.Wimmer, A.Bisianov, D.N. Christodoulides, R.Morandotti, U. Peschel / „ Nonlinear Wave Collapse at mW-Power”: Photonics North, Montreal 2018

  • A.L.M. Muniz, M.Wimmer, A.Bisianov, D.N. Christodoulides, R.Morandotti, U. Peschel / „ Nonlinear Wave Collapse at mW-Power”: Photonics North, Montreal 2018

  • Arstan Bisianov, Mark Kremer, Martin Wimmer, Ulf Peschel / „Experiments on Nonlinearity-Driven Excitation of Topological and Trivial states”: Photonics North, Montreal 2018

  • Kay Schaarschmidt, Markus A. Schmidt / „Higher-Order Mode Third Harmonic Generation in Liquid-Core-Optical-Fiber using ultrafast pulses”: Photonics North, Montreal 2018

 

 

2017

show Content B. Doherty, A. Csáki, M. Thiele, M. Zeisberger, A. Schwuchow, J. Kobelke, W. Fritzsche, and M. Schmidt, "Nanoparticle functionalised small-core suspended-core fibre – a novel platform for efficient sensing," Biomed. Opt. Express 8, 790-799 (2017).

Abstract

Detecting small quantities of specific target molecules is of major importance within bioanalytics for efficient disease diagnostics. One promising sensing approach relies on combining plasmonically-active waveguides with microfluidics yielding an easy-to-use sensing platform. Here we introduce suspended-core fibres containing immobilised plasmonic nanoparticles surrounding the guiding core as a concept for an entirely integrated optofluidic platform for efficient refractive index sensing. Due to the extremely small optical core and the large adjacent microfluidic channels, over two orders of magnitude of nanoparticle coverage densities have been accessed with millimetre-long sample lengths showing refractive index sensitivities of 170 nm/RIU for aqueous analytes where the fibre interior is functionalised by gold nanospheres. Our concept represents a fully integrated optofluidic sensing system demanding small sample volumes and allowing for real-time analyte monitoring, both of which are highly relevant within invasive bioanalytics, particularly within molecular disease diagnostics and environmental science.

doi:10.1364/BOE.8.000790

show Content B. Doherty, M. Thiele, S. Warren-Smith, E. Schartner, H. Ebendorff-Heide, W. Fritzsche, M. A. Schmidt, "Plasmonic nanoparticle-functionalized exposed-core fiber—an optofluidic refractive index sensing platform," Opt. Lett.42, 4395-4398 (2017)

Abstract

Here, we show that immobilizing ensembles of gold nanospheres within tailored areas on the open side of an exposed-core microstructured fiber yields a monolithic, highly sensitive plasmon-based refractive index sensor. The nanoparticle densities (average nanoparticle diameter: 45 nm) on the small-core fiber (core diameter: 2.5 μm) are controlled electrostatically, yielding densities of 4  nanoparticles/μm2. Refractive index sensitivities of 200 nm/RIU for aqueous analytes at high fringe contrast levels (−20  dB) have been observed. Our concept presents an easy-to-use, efficient, and multiplex-compatible sensing platform for rapid small-volume detection with the capacity for integration into a bioanalytic, optofluidic, or microfluidic system.

doi:10.1364/OL.42.004395

show Content M. Falge, F.G. Fröbel, V. Engel, and S. Gräfe, "Time-resolved photoelectron spectroscopy of IR-driven electron dynamics in a charge transfer model system," Phys. Chem. Chem. Phys. 19, 19683 (2017).

Abstract

If the adiabatic approximation is valid, electrons smoothly adapt to molecular geometry changes. In contrast, as a characteristic of diabatic dynamics, the electron density does not follow the nuclear motion. Recently, we have shown that the asymmetry in time-resolved photoelectron spectra serves as a tool to distinguish between these dynamics [Falge et al., J. Phys. Chem. Lett., 2012, 3, 2617]. Here, we investigate the influence of an additional, moderately intense infrared (IR) laser field, as often applied in attosecond time-resolved experiments, on such asymmetries. This is done using a simple model for coupled electronic-nuclear motion. We calculate time-resolved photoelectron spectra and their asymmetries and demonstrate that the spectra directly map the bound electron–nuclear dynamics. From the asymmetries, we can trace the IR field-induced population transfer and both the field-driven and intrinsic (non-)adiabatic dynamics. This holds true when considering superposition states accompanied by electronic coherences. The latter are observable in the asymmetries for sufficiently short XUV pulses to coherently probe the coupled states. It is thus documented that the asymmetry is a measure for phases in bound electron wave packets and non-adiabatic dynamics.

doi:10.1039/c7cp01832k

show Content M. Gebhardt, C. Gaida, F. Stutzki, S. Hädrich, C. Jauregui, J. Limpert, and A. Tünnermann, "High average power nonlinear compression to 4  GW, sub-50  fs pulses at 2  μm wavelength," Opt. Lett. 42, 747-750 (2017).

Abstract

The combination of high-repetition-rate ultrafast thulium-doped fiber laser systems and gas-based nonlinear pulse compression in waveguides offers promising opportunities for the development of high-performance few-cycle laser sources at 2 μm wavelength. In this Letter, we report on a nonlinear pulse compression stage delivering 252 μJ, sub-50 fs-pulses at 15.4 W of average power. This performance level was enabled by actively mitigating ultrashort pulse propagation effects induced by the presence of water vapor absorptions.

doi:10.1364/OL.42.000747

show Content M. Gebhardt et al , "Nonlinear pulse compression to 43  W GW-class few-cycle pulses at 2  μm wavelength," Opt. Lett. 42, 4179-4182 (2017).

Abstract

High-average power laser sources delivering intense few-cycle pulses in wavelength regions beyond the near infrared are promising tools for driving the next generation of high-flux strong-field experiments. In this work, we report on nonlinear pulse compression to 34.4 μJ-, 2.1-cycle pulses with 1.4 GW peak power at a central wavelength of 1.82 μm and an average power of 43 W. This performance level was enabled by the combination of a high-repetition-rate ultrafast thulium-doped fiber laser system and a gas-filled antiresonant hollow-core fiber.

doi:10.1364/OL.42.004179

show Content L. Maczewsky, J. M.Zeuner, S. Nolte, A. Szameit, "Observation of photonic anomalous Floquet topological insulators," Nat. Commun. 8, 13756 (2017).

Abstract

Topological insulators are a new class of materials that exhibit robust and scatter-free transport along their edges — independently of the fine details of the system and of the edge — due to topological protection. To classify the topological character of two-dimensional systems without additional symmetries, one commonly uses Chern numbers, as their sum computed from all bands below a specific bandgap is equal to the net number of chiral edge modes traversing this gap. However, this is strictly valid only in settings with static Hamiltonians. The Chern numbers do not give a full characterization of the topological properties of periodically driven systems. In our work, we implement a system where chiral edge modes exist although the Chern numbers of all bands are zero. We employ periodically driven photonic waveguide lattices and demonstrate topologically protected scatter-free edge transport in such anomalous Floquet topological insulators.

doi:10.1038/ncomms13756

show Content R. Sollapur et al., "Resonance-enhanced multi-octave supercontinuum generation in antiresonant hollow-core fibers," Light: Science & Applications (2017)

Abstract

Ultrafast supercontinuum generation in gas-filled waveguides is an enabling technology for many intriguing applications ranging from attosecond metrology towards biophotonics, with the amount of spectral broadening crucially depending on the pulse dispersion of the propagating mode. In this study, we show that structural resonances in a gas-filled antiresonant hollow core optical fiber provide an additional degree of freedom in dispersion engineering, which enables the generation of more than three octaves of broadband light that ranges from deep UV wavelengths to near infrared. Our observation relies on the introduction of a geometric-induced resonance in the spectral vicinity of the ultrafast pump laser, outperforming gas dispersion and yielding a unique dispersion profile independent of core size, which is highly relevant for scaling input powers. Using a krypton-filled fiber, we observe spectral broadening from 200 nm to 1.7 μm at an output energy of approximately 23 μJ within a single optical mode across the entire spectral bandwidth. Simulations show that the frequency generation results from an accelerated fission process of soliton-like waveforms in a non-adiabatic dispersion regime associated with the emission of multiple phase-matched Cherenkov radiations on both sides of the resonance. This effect, along with the dispersion tuning and scaling capabilities of the fiber geometry, enables coherent ultra-broadband and high-energy sources, which range from the UV to the mid‐infrared spectral range.

doi: 10.1038/lsa.2017.124

show Content D. Richter et al., "Minimizing residual spectral drift in laser diode bars using femtosecond-written volume Bragg gratings in fused silica," Opt. Lett. 42, 623 (2017).

Abstract

Ultrashort laser pulses are used to inscribe volume Bragg gratings (VBGs) into fused silica. These VBGs demonstrate excellent performance for the external stabilization of laser diode bars. The stabilized system emits at a wavelength of 969 nm with a signal width (FWHM) of 100 pm and shows a spectral drift as low as 24 pm for a change in output power of 45 W for a grating surface area of 10  mm2 .

doi:10.1364/OL.42.000623

show Content T. A. Goebel et al., "Flexible femtosecond inscription of fiber Bragg gratings by an optimized deformable mirror," Opt.Lett. 42, 4215 (2017)

Abstract

The period of fiber Bragg gratings is adapted by shaping the wavefronts of ultrashort laser pulses applied in a phase mask inscription technique. A specially designed deformable mirror, based on a dielectric substrate to withstand high peak powers, is utilized to deform the wavefront. A shift of about 11 nm is demonstrated for a Bragg wavelength around 1550 nm.

doi:10.1364/OL.42.004215

show Content M. Chemnitz, M. Gebhardt, C. Gaida, F. Stutzki, J. Kobelke, J. Limpert, A. Tünnermann, and M. A. Schmidt, "Hybrid soliton dynamics in liquid-core fibres," Nat. Commun. 8, 42 (2017).

Abstract

Liquid-core fibers offer local external control over pulse dispersion due to their strong thermodynamic response, offering a new degree of freedom in accurate soliton steering for reconfigurable nonlinear light generation. Here, we show how to accurately control soliton dynamics and supercontinuum generation in carbon disulfide/silica fibers by temperature and pressure tuning, monitored via the spectral location and the onset energy of non-solitonic radiation. Simulations and phase-matching calculations based on an extended thermodynamic dispersion model of carbon disulfide confirm the experimental results, which allows us to demonstrate the potential of temperature detuning of liquid-core fibers for octave spanning recompressible supercontinuum generation in the near-infrared.

doi:10.1364/OPTICA.5.000695

show Content J. Buldt, M. Müller, R. Klas, T. Eidam, J. Limpert, A. Tünnermann, "Temporal contrast enhancement of energetic laser pulses by filtered self-phase-modulation-broadened spectra," Opt. Lett. 42, 3761 (2017).

Abstract

We present a novel approach for temporal contrast enhancement of energetic laser pulses by filtered self-phase-modulation-broadened spectra. A measured temporal contrast enhancement by at least seven orders of magnitude in a simple setup has been achieved. This technique is applicable to a wide range of laser parameters and poses a highly efficient alternative to existing contrast-enhancement methods.

doi:10.1364/OL.42.003761

show Content M. Müller, A. Klenke, T. Gottschall, R. Klas, C. Rothhardt, S. Demmler, J. Rothhardt, J. Limpert, and A. Tünnermann, "High-average-power femtosecond laser at 258 nm," Opt. Lett. 42, 2826 (2017).

Abstract

We present an ultrafast fiber laser system delivering 4.6 W average power at 258 nm based on two-stage fourth-harmonic generation in beta barium borate (BBO). The beam quality is close to being diffraction limited with an M2 value of 1.3×1.6 . The pulse duration is 150 fs, which, potentially, is compressible down to 40 fs. A plain BBO and a sapphire-BBO compound are compared with respect to the achievable beam quality in the conversion process. This laser is applicable in scientific and industrial fields. Further scaling to higher average power is discussed.

doi:10.1364/OL.42.002826

show Content M. Wimmer, H. M. Price, I. Carusotto and U. Peschel, "Experimental measurement of the Berry curvature from anomalous transport," Nature Phys. 13, 545 (2017).

Abstract

The geometric properties of energy bands underlie fascinating phenomena in many systems, including solid-state, ultracold gases and photonics. The local geometric characteristics such as the Berry curvature can be related to global topological invariants such as those classifying the quantum Hall states or topological insulators. Regardless of the band topology, however, any non-zero Berry curvature can have important consequences, such as in the semi-classical evolution of a coherent wavepacket. Here, we experimentally demonstrate that the wavepacket dynamics can be used to directly map out the Berry curvature. To this end, we use optical pulses in two coupled fibre loops to study the discrete time evolution of a wavepacket in a one-dimensional geometric ‘charge’ pump, where the Berry curvature leads to an anomalous displacement of the wavepacket. This is both the first direct observation of Berry curvature effects in an optical system, and a proof-of-principle demonstration that wavepacket dynamics can serve as a high-resolution tool for mapping out geometric properties.

doi:10.1038/nphys4050

show Content Presentations at conferences

Poster

  • B. Doherty, "Plasmonic Nanoparticles in Microstructured Fibres as Detection Platforms". NanoBioSensors conference, TU Dresden.

  • F. G. Fröbel, "Analysis of avoided crossings in molecular model systems," DPG Spring Meeting, Mainz Germany (Mar 2017).

  • M. Gebhardt, "Multi-GW, 100 fs thulium-doped fiber laser system for high-harmonic generation at high repetition rates". CLEO EU 2017 (CJ-11.1 THU).

  • M. Gebhardt, C. Gaida, F. Stutzki, S. Hädrich, C. Jauregui, J. Limpert, A. Tünnermann, "High-average power 4 GW pulses with sub-8 optical cycles from a Tm-doped fiber laser driven nonlinear pulse compression stage", Proc. SPIE 10083, Fiber Lasers XIV: Technology and Systems, 100830B (22 February 2017).

  • M. Gebhardt, C. Gaida, F. Stutzki, C. Jauregui, J. Antonio-Lopez, A. Schulzgen, R. Amezcua-Correa, J. Limpert, and A. Tünnermann, "High average power nonlinear self-compression to few-cycle pulses at 2 µm wavelength in antiresonant hollow-core fiber," in Laser Congress 2017 (ASSL, LAC), OSA Technical Digest (online) (Optical Society of America, 2017), paper ATh3A.6.

  • K. Lammers, "Manipulating Polarization States in Waveguides Using Femtosecond Laser Direct Written.

  • F. J. F. Löchner et al.,  "Polarization dependence of second-harmonic generation in GaAs.

  • Tobias Bucher, Franz J. F. Lochner et al., "Integration of MoS2 Monolayers with Dielectric Nanoantennas".  PIERS St. Petersburg 2017, St. Petersburg, Russia.

  • Aleksandr Vaskin , F. J. F. Lochner et al., "Tailoring Light Emission with Monolithic Nanoantenna Arrays Based on III-V Semiconductors". PIERS St. Petersburg 2017, St. Petersburg, Russia.

  • R. Sollapur, D. Kartashov, M. Zürch, A. Hoffmann, T. Grigorova, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Dispersion-Designed Antiresonant Hollow-Core Fibers for Supercontinuum Generation by Soliton Explosion”, Conference on Lasers and Electro-Optics/Europe and the European Quantum Electronics, 2017.

  • Ni. Jayakumar, R. Sollapur, A. Hoffmann, T. Grigorova, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Polarization Evolution in  Antiresonant Hollow-Core Fibers, DoKDoK – Doctoral Student Conference on Optics, Suhl, Germany, 2017.

  • M. Mircovich, R. Sollapur, A. Hoffmann,  A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Ultraviolet pulse generation and characterization for supercontinuum experiments”, OSAPS Fall Meeting and SOS-AAPT at Miami University, Oxford, USA, 2017.

  • E. Shestaev, “CEP stability of high-power few-cycle fiber lasers”. Ultrafast Optics XI in Jackson Hole, Wyoming, USA (2017).

  • C. Stihler, "Controlling mode instabilities at 628 W average output power in an Yb-doped rodtype fiber amplifier by active modulation of the pump power". Photonics West Conference 2017, San Francisco.

  • C. Stihler, "Mitigation of Mode Instabilities in High-Power Fiber Laser Systems by Active Modulation of the Pump Power". CLEO Europe 2017, München.

Talks

  • Brenda Doherty, "Plasmonic Microstructured Fibres for Biosensing". “20 Years Nano-Optics” international symposium, MPI Erlangen.

  • F. G. Fröbel, "Where the BO-Approximation fails: Analysis of avoided crossings in molecular model systems - An Introduction,"  Institute for Physical Chemistry, Jena (Jan 2017).

  • T. Grigorova, R. Sollapur, N. Jayakumar, A. Hoffmann,  A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Dispersion Measurement of Engineered Antiresonant Hollow‐Core Fibers with Spectral Interferometry”, presented at CLEUO Europe 2017 Munich, Germany.

  • R. Sollapur, D. Kartashov, M. Zürch, A. Hoffmann, T. Grigorova, G. Sauer, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. Chemnitz, M. A. Schmidt C. Spielmann, “Multi-octave supercontinuum in dispersion tuned antiresonant hollow-core fibers”, DoKDoK – Doctoral Student Conference on Optics, Suhl, Germany, 2017.

  • M. Zürch, R. Sollapur, D. Kartashov, A. Hoffmann, T. Grigorova, G. Sauer, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt C. Spielmann, “Multi-octave supercontinuum driven by soliton explosion in dispersion-designed antiresonant hollow-core fibers”, Conference on Lasers and Electro-Optics, 2017.

 

 

 

2016

show Content S. Breitkopf et al., "Extraction of enhanced , ultrashort laser pulses from a passive 10- MHz stack-and-dump cavity, " Appl. Phys. B-Lasers and Optics 122 (2016).

Abstract

Periodic dumping of ultrashort laser pulses from a passive multi-MHz repetition-rate enhancement cavity is a promising route towards multi-kHz repetition-rate pulses with Joule-level energies at an unparalleled average power. Here, we demonstrate this so-called stack-and-dump scheme with a 30-m-long cavity. Using an acousto-optic modulator, we extract pulses of 0.16 mJ at 30-kHz repetition rate, corresponding to 65 stacked input pulses, representing an improvement in three orders of magnitude over previously extracted pulse energies. The ten times longer cavity affords three essential benefits over former approaches. First, the time between subsequent pulses is increased to 100 ns, relaxing the requirements on the switch. Second, it allows for the stacking of strongly stretched pulses (here from 800 fs to 1.5 ns), thus mitigating nonlinear effects in the cavity optics. Third, the choice of a long cavity offers increased design flexibility with regard to thermal robustness, which will be crucial for future power scaling. The herein presented results constitute a necessary step towards stack-and-dump systems providing access to unprecedented laser parameter regimes.

doi:10.1007/s00340-016-6574-x

show Content C. Gaida, M. Gebhardt, F. Stutzki, C. Jauregui, J. Limpert, A. Tünnermann, "Thulium-doped fiber chirped-pulse amplification system with 2 GW of peak power," Opt. Lett. 41 (17), 4130-4133 (2016).

Abstract

Thulium-doped fibers with ultra large mode-field areas offer new opportunities for the power scaling of mid-IR ultrashort-pulse laser sources. Here, we present a laser system delivering a pulse-peak power of 2 GW and a nearly transform-limited pulse duration of 200 fs in combination with 28.7 W of average power. This performance level has been achieved by optimizing the pulse shape, reducing the overlap with atmospheric absorption lines, and incorporating a climate chamber to reduce the humidity of the atmospheric environment.

doi:10.1364/OL.41.004130

show Content S. Hädrich et al., "Energetic sub-2-cycle laser with 216 W average power," Opt. Lett. 41, 4332 (2016).

Abstract

Few-cycle lasers are essential for many research areas such as attosecond physics that promise to address fundamental questions in science and technology. Therefore, further advancements are connected to significant progress in the underlying laser technology. Here, two-stage nonlinear compression of a 660 W femtosecond fiber laser system is utilized to achieve unprecedented average power levels of energetic ultrashort or even few-cycle laser pulses. In a first compression step, 408 W, 320 μJ, 30 fs pulses are achieved, which can be further compressed to 216 W, 170 μJ, 6.3 fs pulses in a second compression stage. To the best of our knowledge, this is the highest average power few-cycle laser system presented so far. It is expected to significantly advance the fields of high harmonic generation and attosecond science.

doi:10.1364/QL.41.004332

show Content R. Klas, S. Demmler, M. Tschernajew, S. Hädrich, Y. Shamir, A. Tünnermann, J. Rothhardt, J. Limpert, "Table-top milliwatt-class extreme ultraviolet high harmonic light source," Optica 3, 1167-1170 (2016).

Abstract

Extreme ultraviolet (XUV) lasers are essential for the investigation of fundamental physics. Especially high repetition rate, high photon flux sources are of major interest for reducing acquisition times and improving signal-to-noise ratios in a plethora of applications. Here, an XUV source based on cascaded frequency conversion is presented, which, due to the drastic better single atom response for short wavelength drivers, delivers an average output power of (832±204)  μW at 21.7 eV. This is the highest average power produced by any high harmonic generation source in this spectral range, surpassing previous demonstrations by almost an order of magnitude. Furthermore, a narrowband harmonic at 26.6 eV has been generated that is of high interest for high-precision spectroscopy experiments.

doi:10.1364/OPTICA.3.001167

show Content M. Müller, M. Kienel, A. Klenke, T. Gottschall, E. Shestaev, M. Plotner, J. Limpert, and A. Tünnermann, "1 kW 1 mJ eight-channel ultrafast fiber laser," Opt. Lett. 41, 3439 (2016).

Abstract

An ultrafast fiber chirped-pulse amplifier comprising eight coherently combined amplifier channels is presented. The laser delivers 1 kW average power at 1 mJ pulse energy and 260 fs pulse duration. Excellent beam quality and low-noise performance are confirmed. The laser has proven suitable for demanding scientific applications. Further power scaling is possible right away using even more amplifier channels.

doi:10.1364/OL.41.003439

show Content J. Rothhardt et al., "High-repetition-rate and high-photon-flux 70 eV high-harmonic source for coincidence ion imaging of gas-phase molecules," Opt. Lett. 41, 3439 (2016).

Abstract

Unraveling and controlling chemical dynamics requires techniques to image structural changes of molecules with femtosecond temporal and picometer spatial resolution. Ultrashort-pulse x-ray free-electron lasers have significantly advanced the field by enabling advanced pump-probe schemes. There is an increasing interest in using table-top photon sources enabled by high-harmonic generation of ultrashort-pulse lasers for such studies. We present a novel high-harmonic source driven by a 100 kHz fiber laser system, which delivers 1011 photons/s in a single 1.3 eV bandwidth harmonic at 68.6 eV. The combination of record-high photon flux and high repetition rate paves the way for time-resolved studies of the dissociation dynamics of inner-shell ionized molecules in a coincidence detection scheme. First coincidence measurements on CH3 I are shown and it is outlined how the anticipated advancement of fiber laser technology and improved sample delivery will, in the next step, allow pump-probe studies of ultrafast molecular dynamics with table-top XUV-photon sources. These table-top sources can provide significantly higher repetition rates than the currently operating free-electron lasers and they offer very high temporal resolution due to the intrinsically small timing jitter between pump and probe pulses.

doi:10.1364/OE.24.018133

show Content G.K. Tadesse, R. Klas, S. Demmler, S. Hädrich, I. Wahyutama, M. Steinert, C. Spielmann, M. Zurch, T. Pertsch, A. Tünnermann, J. Limpert, J. Rothhardt, "High speed and high resolution table-top nanoscale imaging," Opt. Lett. 41 , 5170-5173 (2016).

Abstract

We present a table-top coherent diffractive imaging (CDI) experiment based on high-order harmonics generated at 18 nm by a high average power femtosecond fiber laser system. The high photon flux, narrow spectral bandwidth, and high degree of spatial coherence allow for ultrahigh subwavelength resolution imaging at a high numerical aperture. Our experiments demonstrate a half-pitch resolution of 15 nm, close to the actual Abbe limit of 12 nm, which is the highest resolution achieved from any table-top extreme ultraviolet (XUV) or x-ray microscope. In addition, sub-30 nm resolution was achieved with only 3 s of integration time, bringing live diffractive imaging and three-dimensional tomography on the nanoscale one step closer to reality. The current resolution is solely limited by the wavelength and the detector size. Thus, table-top nanoscopes with only a few-nanometer resolutions are in reach and will find applications in many areas of science and technology.

 doi:10.1364/OL.41.005170

show Content C. Voigtländer, R. G. Krämer, T. A. Goebel, D. Richter, and S. Nolte, "Variable wavefront tuning with a SLM for tailored femtosecond fiber Bragg grating inscription," Opt. Lett. 41, 17 (2016)

Abstract

We report on the inscription of fiber Bragg gratings using femtosecond laser pulses and the phase-mask technique. The wavefront of the inscription laser is variably tuned with a spatial light modulator (SLM). By applying Fresnel lenses with different focal lengths, the period of the fiber Bragg gratings could be shifted. A linear change of the grating period for a FBG inscribed with a third-order deformed wavefront and a quadratic-period behavior for a fourth-order wavefront could be verified experimentally for the first time.

 doi:10.1364/OL.41.000017

show Content Presentations at conferences

Talks

  • F. G. Fröbel, "Theoretical Modeling of Nonlinear Optics in Gas-filled Hollow-core Fibers in the Near and Mid-IR - An Introduction,"  Institute for Physical Chemistry, Jena (Feb 2016).

  • F. G. Fröbel, "Theoretical Modeling of Nonlinear Optics in Gas-filled Hollow-core Fibers in the Near and Mid-IR - Status Report, " Abbe School of Photonics, Jena (July 2016).

  • F. G. Fröbel, "Theoretical Modeling of Nonlinear Optics in Gas-filled Hollow-core Fibers in the Near and Mid-IR,"  GRK2101 Summer School, Abbe School of Photonics, Jena (Sep 2016).

  • S. Demmler, T. Eidam, S. Breitkopf, M. Kienel, A. Klenke, M. Müller, F. Stutzki,  H.-J.  Otto, C. Gaida, M. Gebhardt,  G. Tadesse,  T. Gottschall, C. Jauregui, S. Hädrich, J. Rothhardt, T. Schreiber, J. Limpert, A. Tünnermann, "Advances in High Repetition Rate Ultrafast Lasers - Novel Avenues in Science and Industry," HPLA/DE (High Power Laser Ablation and Directed Energy), Santa Fe USA ( 2016).
  • M. Gebhardt, C. Gaida, F. Stutzki, S. Hädrich, C. Jauregui, J. Limpert, and A. Tünnermann, "Self-compression to 24 MW peak power in a fused silica solid-core fiber using a high-repetition rate thulium-based fiber laser system," Photonics West LASE, San Francisco USA (2016).

  • M. Gebhardt, C. Gaida, R. Klas, F. Stutzki, S. Hädrich, S. Demmler, J. Rothhardt, C. Jauregui, J. Limpert, and A. Tünnermann, " High-power nonlinear compression stage delivering sub-50 fs, 0.25 mJ pulses, 15 W at 2 μm wavelength for HHG," ASSL, LSC, LAC, Boston USA (2016).

  • C. Gaida, M. Gebhardt, F. Stutzki, H.-J.  Otto, C. Jauregui, J. Limpert, A. Tünnermann," Average power scaling of ultrashort-pulse Tm-based fiber laser systems," Photonics West LASE, San Francisco USA (2016).

  • C. Gaida, M. Gebhardt, F. Stutzki, S. Hädrich, C. Jauregui, J. Limpert, A. Tünnermann, "High average power GW-level few-cycle pulses at 2 µm wavelength for high photon energy HHG," HILAS; Los Angeles USA (2016).

  • M. Chemnitz, M. Gebhardt, C. Gaida, F. Stutzki, J. Limpert, M. A. Schmidt, "Indications of new solitonic states within mid-IR supercontinuum generated in highly non-instantaneous fiber," CLEO, San Jose USA (2016).

  • F. Stutzki, C. Gaida, M. Gebhardt, R. Klas, S. Demmler, S. Hädrich, J. Rothhardt, C. Jauregui, J. Limpert, and A. Tünnermann, "Nonlinear pulse compression and high-harmonic generation driven by a high repetition rate Tm-based fber CPA system," Europhoton Conference, Vienna Austria (2016).

  • C. Gaida, F. Stutzki, M. Gebhardt, C. Jauregui, J. Limpert, and A. Tünnermann, "Prospects for peak power scaling of Tm-doped fiber CPA systems," ASSL, LSC, LAC,  Boston USA (2016).

  • M. Heck, "Femtosecond laser pulse written Long Period Gratings with minimal out-of-band losses," DokDok (2016).

  • M. Kienel, S. Hädrich, M. Müller, A. Klenke, J. Rothhardt, R. Klas, T. Gottschall, T. Eidam, A. Drozdy, P. Jójárt, Z. Várallyay, E. Cormier, K. Osvay, A. Tünnermann, and J. Limpert, "Few-cycle Laser with 216 W Average Power and 6.3 fs Pulses," ASSL, LSC, LAC, Boston USA (2016).

  • J. Rothhardt, R. Klas, M. Tschernajew, S. Demmler, A. Tünnermann, J. Limpert, "Development of high-repetition rate XUV lasers for storage-ring experiments, " 11th SPARC topical Workshop, Krakow Poland (2016)

  • J. Rothhardt, G. K. Tadesse, S. Hädrich, R. Klas, S. Demmler, J. Limpert and A. Tünnermann, "Fiber-laser based high harmonic sources for nanoscale imaging and spectroscopy , " Frontiers in Optics Conference, Rochester USA (2016).

  • J. Rothhardt, G. K. Tadesse, S. Hädrich, R. Klas, S. Demmler, J. Limpert and A. Tünnermann, "Nanoscale imaging with high photon flux table-top XUV sources," IEEE Photonics Conference, Waikoloa USA (20016).

  • S. Demmler, R. Klas, M. Tschernajew, S. Hädrich, J. Rothhardt, J. Limpert, A. Tünnermann, "Narrowband High Harmonic Source with Multi-mW Average Power Based on Cascaded Frequency Conversion," Ultrafast Phenomena, Santa Fe USA (2016).

  • S. Demmler, R. Klas, M. Tschernajew, S. Hädrich, J. Rothhardt, J. Limpert, A. Tünnermann, "mW Average Power Narrowband High Harmonic Sources," in High-Brightness Sources and Light-Driven Interactions (HILAS), Los Angeles USA (2016).

  • R. Klas, S. Demmler, M. Tschernajew, S. Hädrich, J. Rothhardt, J. Limpert, A. Tünnermann, "Milliwatt Class Narrowband High Harmonic Source Based on Cascaded Frequency Conversion," Europhoton Conference, Vienna Austria (2016).

  • G.K. Tadesse, R. Klas, S. Demmler, S. Hädrich, I. Wahyutama, M. Zürch, M. Steinert, C. Spielmann, A. Tünnermann, J. Limpert  and J. Rothhardt, "High photon flux 70 eV high harmonic source for coherent nanoscale imaging," Europhoton Conference, Vienna Austria (2016).

  • G.K. Tadesse, R. Klas, S. Demmler, S. Hädrich, I. Wahyutama, M. Zürch, C. Spielmann, A. Tünnermann, J. Limpert and J. Rothhardt, "Sub-20 nm Resolution Coherent Diffractive Imaging with a Table-Top XUV Source," Coherence Conference, Saint Malo France (2016).

  • G.K. Tadesse, R. Klas, S. Demmler, S. Hädrich, I. Wahyutama, M. Zürch, C. Spielmann, A. Tünnermann, J. Limpert and J. Rothhardt, "Table-top coherent diffractive imaging – towards sub-10 nm resolution," X-Ray Microscopy Conference (XRM), Oxford UK (2016).

  • S. Hädrich, M. Kienel, M. Müller, A. Klenke, J. Rothhardt, R. Klas, T. Gottschall, T. Eidam, A. Drozdy, P. Jojart, Z. Varallyay, E. Cormier, K. Osvay, A. Tünnermann, J. Limpert, "Utilizing fiber lasers to obtain 220W average power energetic sub 2-cycle pulses," Europhoton Conference, Vienna Austria (2016).

  • R. Klas, S. Hädrich, J. Rothhardt, J.Limpert, A. Tünnermann, M. Aeschlimann, M. Barkowski, S. Sadashivaiah, J. Urbancic, S. Mathias, "High Photon Flux 70 eV HHG Source for Ultrafast Dynamics," Ultrafast Phenomena, Santa Fe USA (2016).

  • F. Löchner,  "Second-harmonic generation in MoS2 monolayers coupled to resonant nanoantennas," DPG-Frühjahrstagung Regensburg, Germany  (March 2016).

  • S. Weimann, M. Kremer, L. Maczewsky, J. M. Zeuner, Y. Plotnik, Y. Lumer, K. G. Makris, M. Segev, M.S. Rudner, S. Nolte, M. C. Rechtsman, A. Szameit, " Non-Hermitian Photonics,"  at META conference , Malaga Spain (July 2016).

  • R. Heilmann, M.Gräfe, L. Maczewsky, S. Nolte, A. Szameit, "A highly precise characterization technique for integrated photonic devices," at CLEO , San Jose  California (June 2016).

  • R. Keil, C. Noh, A. Rai, L. Maczewsky, S. Stützer, S. Nolte, D. G. Angelakis, A, Szameit, "Optical simulations of unphysical Majorana dynamics,"  at CLEO , San Jose California (June 2016).

  • S. Weimann, M. Kremer, L. Maczewsky, J. M. Zeuner, Y. Plotnik, Y. Lumer, K. G. Makris, M. Segev, M.S. Rudner, S. Nolte, M. C. Rechtsman, A. Szameit,  "Non-Hermitian Photonics," at DokDok conference , Malaga Spain (Sep 2016).

  • S. Breitkopf, S. Wunderlich, T. Eidam, E. Shestaev, T. Gottschall, H. Carstens, S. Holzberger, T. Gottschall, H. Carstens, A. Tünnermann, I. Pupeza, and J. Limpert, "Extraction of enhanced, ultrashort laser pulses from a passive 10- MHz stack-and-dump cavity,"  Europhoton Conference, Vienna Austria (2016).

  • S. Breitkopf, S. Wunderlich, T. Eidam, E. Shestaev, T. Gottschall, H. Car- stens, S. Holzberger, I. Pupeza, J. Limpert, and A. Tünnermann, "Investigation of a 10 MHz, non-steady state cavity for pulse energy enhancement of ultrafast fiber lasers," Photonics West LASE, San Francisco USA (2016).

  • A. Klenke, M. Kienel, M. Müller, T. Gottschall, S. Breitkopf, E. Shestaev, C. Jauregui, J. Rothhard, T. Eidam, S. Hädrich, J. Limpert,  A. Tünnermann, "Coherent combination of fiber lasers ," ICUIL, Montebello Canada (2016).

  • A. Klenke, M. Kienel, M. Müller, T. Gottschall, S. Breitkopf, E. Shestaev, C. Jauregui, J. Rothhard, T. Eidam, S. Hädrich, J. Limpert,  A. Tünnermann, "Leistungssteigerungskonzepte für Femtosekundenfaserlaser," Optische Fasern - Aktuelle Trends und zukünftige Entwicklungen, Nürnberg Germany (2016).

  • M Müller, M. Kienel, A. Klenke, T. Gottschall, E. Shestaev, J. Limpert, A. Tünnermann, " 11.7 mJ pulse energy kW-class average power 8-channel ultrafast fibre laser," Europhoton, Vienna Austria (2016).
  • C. Stihler, C. Jauregui, H.-J. Otto, J. Limpert and A.Tünnermann," The impact of photodarkening on the mode instability threshold," DokDok 2016, Oppburg Germany (2016).

  • C. Stihler, C. Jauregui, H.-J. Otto, J. Limpert and A.Tünnermann,"The impact of photodarkening on the mode instability threshold," GRK 2101 - Summer School, Jena Germany (2016). 

  • C. Jauregui, H.-J. Otto, C. Stihler, J. Limpert, A. Tünnermann, "Thermal optimization of high power fiber laser systems," Laser Optics, St. Petersburg Russia (2016).
  • M.Zürch, R. Sollapur, A. Hoffmann, G. Sauer, A. Hartung, D. Kartashov, M. Schmidt,  C. Spielmann, „Octave Broadband Supercontinuum Generation in Gas-Filled Anti-Resonant Hollow-Core Fiber“, CLEO  invited presentation (2016).

  • R. Sollapur, D. Kartashov, M. Zürch, A. Hoffmann, T. Grigorova, G. Sauer, A. Hartung, A. Schwuchow, J. Bierlich, J. Kobelke, M. A. Schmidt, C. Spielmann, “Multi-octave supercontinuum generation in anti-resonant hollow core fibers”, Summer School of the GRK 2101, Abbe Center of Photonics, Jena Germany (2016).

Poster

  • R. Sollapur, M.Zürch,  A. Hoffmann, G. Sauer,  D. Kartashov, M. Schmidt,  C. Spielmann, "Nonlinear optics in gas-filled hollow-core fibers in the near and mid-IR,“  DokDok student conference (2015).

  • R. Sollapur, M.Zürch,  A. Hoffmann, G. Sauer,  D. Kartashov, M. Schmidt,  C. Spielmann, "Nonlinear optics in gas-filled hollow-core fibers in the near and mid-IR,” German Canadian Workshop, University of Toronto Canada (2015).

  • R. Sollapur, M.Zürch,  A. Hoffmann, G. Sauer,  D. Kartashov, M. Schmidt,  C. Spielmann, "Nonlinear optics in gas-filled hollow-core fibers in the near and mid-IR”, The international Workshop “New Frontiers in Fiber Optics” , Leibniz Institute of Photonic Technology, Jena Germany (2016).

  • R. Sollapur, M.Zürch,  A. Hoffmann, G. Sauer,  D. Kartashov, A. Hartung, M. Schmidt,  C. Spielmann, "Multi-octave supercontinuum generation in gas-filled anti-resonant hollow-core fiber”, Siegman International School on Lasers, The Institute of Photonic Sciences, Barcelona Spain (2016).

  • A. Hoffmann, M. Zürch, R. Sollapur, D. Kartashov, T. Grigorova, G. Sauer, A. Hartung, M. Schmidt, ChriC.stian Spielmann, "Scaling supercontinuum generation in gas-lled hollow-core fibers “, Europhoton (2016).

  • T. Grigorova, R. Sollapur, A. Hoffmann, M. Schmidt, A. Hartung, M. Schmidt, C. Spielmann, "Dispersion measurements of a novel anti-resonant hollow-core fiber, “ DokDok student conference (2016).

 

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