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Publikationen von
Dr. Christoph Heyl

Alle Publikationen des HI Jena

2022

M. Seidel, F. Pressacco, O. Akcaalan, T. Binhammer, J. Darvill, N. Ekanayake, M. Frede, U. Grosse-Wortmann, M. Heber, C. Heyl, D. Kutnyakhov, C. Li, C. Mohr, J. Mueller, O. Puncken, H. Redlin, N. Schirmel, S. Schulz, A. Swiderski, H. Tavakol, H. Tuennermann, C. Vidoli, L. Wenthaus, N. Wind, L. Winkelmann, B. Manschwetus, and I. Hartl
Ultrafast MHz-Rate Burst-Mode Pump-Probe Laser for the FLASH FEL Facility Based on Nonlinear Compression of ps-Level Pulses from an Yb-Amplifier Chain
Laser & Photonics Reviews 1, 2100268 (2022)

Abstract: The Free-Electron Laser (FEL) FLASH offers the worldwide still unique capability to study ultrafast processes with high-flux, high-repetition rate extreme ultraviolet, and soft X-ray pulses. The vast majority of experiments at FLASH are of pump-probe type. Many of them rely on optical ultrafast lasers. Here, a novel FEL facility laser is reported which combines high average power output from Yb:YAG amplifiers with spectral broadening in a Herriott-type multipass cell and subsequent pulse compression to sub-100-fs durations. Compared to other facility lasers employing optical parametric amplification, the new system comes with significantly improved noise figures, compactness, simplicity, and power efficiency. Like FLASH, the optical laser operates with 10-Hz burst repetition rate. The bursts consist of 800-mu s long trains of up to 800 ultrashort pulses being synchronized to the FEL with femtosecond precision. In the experimental chamber, pulses with up to 50-mu J energy, 60-fs full-width half-maximum duration and 1-MHz rate at 1.03-mu m wavelength are available and can be adjusted by computer-control. Moreover, nonlinear polarization rotation is implemented to improve laser pulse contrast. First cross-correlation measurements with the FEL at the plane-grating monochromator photon beamline are demonstrated, exhibiting the suitability of the laser for user experiments at FLASH.

E. Escoto, A.-L. Viotti, S. Alisauskas, H. Tunnermann, I. Hartl, and C. Heyl
Temporal quality of post-compressed pulses at large compression factors
Journal of the Optical Society of America B 39, 1694 (2022)

Abstract: Post-compression of ultra-short laser pulses via self-phase modulation is routinely employed for the generation of laser pulses with optical bandwidths reaching far beyond the laser gain limitations. Although high compression factors can be routinely achieved, the compressed pulses typically suffer from temporal quality degradation. We numerically and experimentally analyze the deterioration of different measures of temporal quality with increasing compression factor and show how appropriate dispersion management and cascading of the post-compression process can be employed to limit the impact of this effect. The demonstrated saturation of pulse quality degradation at large compression factors puts novel femtosecond laser architectures based on post-compressed picosecond or even nanosecond laser systems in sight.

A.-L. Viotti, M. Seidel, E. Escoto, S. Rajhans, W. Leemans, I. Hartl, and C. Heyl
Multi-pass cells for post-compression of ultrashort laser pulses
Optica 9, 197 (2022)

Abstract: Ultrafast lasers reaching extremely high powers within short fractions of time enable a plethora of applications. They grant advanced material processing capabilities, are effective drivers for secondary photon and particle sources, and reveal extreme light-matter interactions. They also supply platforms for compact accelerator technologies, with great application prospects for tumor therapy or medical diagnostics. Many of these scientific cases benefit from sources with higher average and peak powers. Following mode-locked dye and titanium-doped sapphire lasers, broadband optical parametric amplifiers have emerged as high peak- and average power ultrashort pulse lasers. A much more power-efficient alternative is provided by direct post-compression of high-power diode-pumped ytterbium lasers-a route that advanced to another level with the invention of a novel spectral broadening approach, the multi-pass cell technique. The method has enabled benchmark results yielding sub-50-fs pules at average powers exceeding 1 kW, has facilitated femtosecond post-compression at pulse energies above 100 mJ with large compression ratios, and supports picosecond to few-cycle pulses with compact setups. The striking progress of the technique in the past five years puts light sources with tens to hundreds of TW peak and multiple kW of average power in sight-an entirely new parameter regime for ultrafast lasers. In this review, we introduce the underlying concepts and give brief guidelines for multi-pass cell design and implementation. We then present an overview of the achieved performances with both bulk and gas-filled multipass cells. Moreover, we discuss prospective advances enabled by this method, in particular including opportunities for applications demanding ultrahigh peak-power, high repetition rate lasers such as plasma accelerators and laser-driven extreme ultraviolet sources.

C. Mahnke, Y. Hua, Y. Ma, S. Salman, T. Lamb, S. Schulz, C. Heyl, H. Cankaya, and I. Hartl
Long-term stable, synchronizable, low-noise picosecond Ho:fiber NALM oscillator for Ho:YLF amplifier seeding
Optics letters 47, 822 (2022)

Abstract: We demonstrate a 41.6 MHz, 1.3 ps, 140 pJ Ho:fiber oscillator using a nonlinear amplifying loop mirror (NALM) as saturable absorber. The oscillator is constructed entirely with polarization-maintaining (PM) fibers, is tunable with a center wavelength between 2035 nm and 2075 nm, and can be synchronized to an external RF reference. For our application of Ho:YLF amplifier seeding for dielectric electron acceleration, the laser is tuned to 2050 nm and synchronized to a stable RF reference with 45 fs rms timing jitter in the integration interval [10 Hz, 1 MHz]. We show long term synchronized operation and characterize the relative intensity noise (RIN) and timing jitter of the oscillator for two different Tm-fiber pump lasers.

C. Heyl, M. Seidel, E. Escoto, A. Schoenberg, S. Carlstroem, G. Arisholm, T. Lang, and I. Hartl
High-energy bow tie multi-pass cells for nonlinear spectral broadening applications
Journal of Physics-Photonics 4, 014002 (2022)

Abstract: Multi-pass cells (MPCs) have emerged as very attractive tools for spectral broadening and post-compression applications. We discuss pulse energy limitations of standard MPCs considering basic geometrical scaling principles and introduce a novel energy scaling method using a MPC arranged in a bow tie geometry. Employing nonlinear pulse propagation simulations, we numerically demonstrate the compression of 125 mJ, 1 ps pulses to 50 fs using a compact 2 m long setup and outline routes to extend our approach into the Joule-regime.

2021

E. Appi, C. C. Papadopoulou, J. L. Mapa, C. Jusko, P. Mosel, A. Schoenberg, J. Stock, T. Feigl, S. Ališauskas, T. Lang, C. M. Heyl, B. Manschwetus, M. Brachmanski, M. Braune, H. Lindenblatt, F. Trost, S. Meister, P. Schoch, A. Trabattoni, F. Calegari, R. Treusch, R. Moshammer, I. Hartl, U. Morgner, and M. Kovacev
Synchronized beamline at FLASH2 based on high-order harmonic generation for two-color dynamics studies
Review of Scientific Instruments 92, 123004 (2021)
Kein Abstract vorhandenLinkBibTeX
A.-L. Viotti, S. Alisauskas, H. Tuennermann, E. Escoto, M. Seidel, K. Dudde, B. Manschwetus, I. Hartl, and C. Heyl
Temporal pulse quality of a Yb:YAG burst-mode laser post-compressed in a multi-pass cell
Optics Letters 46, 4686 (2021)

Abstract: Nonlinear pulse post-compression represents an efficient method for ultrashort, high-quality laser pulse production. The temporal pulse quality is, however, limited by amplitude and phase modulations intrinsic to post-compression. We here characterize in frequency and time domain with high dynamic range individual post-compressed pulses within laser bursts comprising 100-kHz-rate pulse trains. We spectrally broaden 730 fs, 3.2 mJ pulses from a Yb:YAG laser in a gas-filled multi-pass cell and post-compress them to 56 fs. The pulses exhibit a nearly constant energy content of 78% in the main peak over the burst plateau, which is close to the theoretical limit. Our results demonstrate attractive pulse characteristics, making multi-pass post-compressed lasers very applicable for pump-probe spectroscopy at, e.g., free-electron lasers or as efficient drivers for secondary frequency conversion stages.

Y. Ma, S. Salman, C. Li, C. Mahnke, Y. Hua, S. Droste, J. Fellinger, A. Mayer, O. Heckl, C. Heyl, and I. Hartl
Compact, All-PM Fiber Integrated and Alignment-Free Ultrafast Yb:Fiber NALM Laser With Sub-Femtosecond Timing Jitter
Journal of Lightwave Technology 39, 4431 (2021)
Kein Abstract vorhandenLinkBibTeX
S. Salman, Y. Ma, K. Gürel, S. Schilt, C. Li, P. Pfäfflein, C. Mahnke, J. Fellinger, S. Droste, A. Mayer, O. Heckl, T. Südmeyer, C. Heyl, and I. Hartl
Comparison of two low-noise CEO frequency stabilization methods for an all-PM Yb:fiber NALM oscillator
OSA Continuum 4, 1889 (2021)
Kein Abstract vorhandenLinkBibTeX
A.-L. Viotti, S. Alisauskas, A. Bin Wahid, P. Balla, N. Schirmel, B. Manschwetus, I. Hartl, and C. Heyl
60 fs, 1030nm FEL pump--probe laser based on a multi-pass post-compressed Yb:YAG source
Journal of Synchrotron Radiation 28, 36 (2021)

Abstract: This paper reports on nonlinear spectral broadening of 1.1ps pulses in a gas-filled multi-pass cell to generate sub-100fs optical pulses at 1030nm and 515nm at pulse energies of 0.8mJ and 225\textdollar µ \textdollar J, respectively, for pump--probe experiments at the free-electron laser FLASH. Combining a 100kHz Yb:YAG laser with\textasciitilde 180W in-burst average power and a post-compression platform enables reaching simultaneously high average powers and short pulse durations for high-repetition-rate FEL pump--probe experiments.

A. Schonberg, H. S. Salman, A. Tajalli, I. Hartl, and C. M. Heyl
7th harmonic generation in gases for coherent 150 nm light production
(2021)

Abstract: High-harmonic-generation in gases (HHG), along with crystal-based nonlinear frequency conversion, represent well established methods for laser-light production, covering spectral regions from soft X-rays down to the terahertz regime. A less-explored intermediate spectral regime can be identified in-between the spectral regions covered by these two methods, characterized by the cut-off wavelength of nonlinear crystals (e.g. KBBF around 160 nm) and the ionization potential of nonlinear gas media (e.g. Xenon at 102 nm). This wavelength regime is currently attracting increasing attention, brought along by measurements of the nuclear clock transition energy of the Thorium-229 isotope at a wavelength of 149.7 ± 3.1 nm [1] . Compared to alternative approaches such as cascaded frequency up-conversion in a hollow capillary [2] or four-wave-mixing processes, the simplest method to producing 150 nm light is the direct generation of the 7 th harmonic of a 1030 nm Ytterbium (Yb) laser source. In particular, it is easily compatible with demonstrated methods for vacuum-ultraviolet frequency comb production via intra-cavity harmonic generation [3] . However, in contrast to HHG, where phase-matching is commonly reached, for 7 th harmonic generation in gases all key phase-mismatch contributions (Gouy phase, neutral- and plasma dispersion) have the same sign. In this work, we demonstrate 7 th harmonic generation in a noble gas-jet driven by a 1025 nm Yb laser source. We measure a maximum conversion efficiency of η ≅ 5 × 10 -6 for two different nozzle orifice diameters for Krypton and Argon, limited mainly by phase-matching effects.

A.-L. Viotti, S. Alisauskas, H. Tunnermann, E. Escoto, M. Seidel, K. Dudde, B. Manschwetus, I. Hartl, and C. Heyl
Intra-Burst Pulse Characterization of a High-Power Post-Compressed Yb:YAG Laser at 100 kHz Repetition Rate
(2021)

Abstract: High-average power Ytterbium (Yb) laser systems are playing an increasingly important role in ultrafast science e.g. as pump lasers for optical parametric amplifiers or directly as ultrafast sources. The gain bandwidth of Yb limits the pulse duration to a few 100 fs up to about 1 ps. However, many applications, such as attosecond physics or X-ray Free Electron Laser (FEL) science, would greatly benefit from the combination of high average powers with much shorter pulses, achievable via post-compression. Nonlinear pulse post-compression of high-average power Yb lasers employing multi-pass cell (MPC) -based spectral broadening [1] , [2] was recently implemented for two burst-mode pump-probe lasers at the FEL facility FLASH in Hamburg [3] , [4] . For such lasers, precise characterization and control of intra-burst pulse dynamics is crucial as the post-compression process couples input pulse energy instabilities with important output pulse parameters such as spectrum, pulse length and temporal contrast. Here, we demonstrate 100 kHz intra-burst spectrum, phase and temporal contrast characterization of a Yb:YAG Innoslab burst-mode amplifier post-compressed in a gas-filled MPC. Our measurements reveal a stable broadened spectrum and compressed pulse duration within the flat part of the burst, yielding a relative energy content of about 80% in the main compressed fs pulse (250 fs window versus 4 ps background pedestal).

E. Escoto, A.-L. Viotti, S. Alisauskas, H. Tunnermann, M. Seidel, K. Dudde, B. Manschwetus, I. Hartl, and C. M. Heyl
Role of dispersion and compression ratio on the temporal contrast of SPM-broadened post-compressed pulses
(2021)

Abstract: Nonlinear pulse post-compression, mainly enabled by self-phase modulation (SPM), opens new avenues towards high peak power laser pulses at high average power while bypassing the need for a gain medium with large bandwidth. However, SPM-induced spectral broadening typically introduces spectral amplitude modulations as well as a chirp of third and higher orders, limiting the temporal contrast of the compressed pulse. While some recent works address this issue and discuss mitigation strategies [1] , [2] , not much attention has been devoted to the physical processes and limitations that determine the temporal contrast of post-compressed pulses. As novel compression techniques expand the achievable compression ratio [3] , it is increasingly important to fully understand the underlying pulse quality limitations. Here, we outline the role of two important characteristics — dispersion and compression ratio — on the temporal quality of post-compressed pulses. Using both numerical simulations as well as experimental tests employing a gas-filled multi-pass cell (MPC), we study the temporal contrast of post-compressed pulses over large compression-ratio and dispersion range. Using a 730 fs input pulse we were able to generate a 55 fs post-compressed pulse with up to 78% energy contained in the main compressed pulse (defined via the first local minima near the highest peak) against its picosecond background.

A.-L. Viotti, S. Alisauskas, E. Escoto, H. Tünnermann, K. Dudde, M. Seidel, B. Manschwetus, I. Hartl, and C. M. Heyl
Intra-Burst Temporal Pulse Contrast of a High-Power Post-Compressed Picosecond Yb:YAG Laser
(2021)

Abstract: We report on pulse contrast characterization of the output of a gas-filled multi-pass cell employed for 20-fold compression of a high-power Yb:YAG laser. We demonstrate an energy content of 80% in the compressed fs pulse.

C. Heyl
Multi-pass post-compression of ultrashort laser pulses at extreme parameter scales
(2021)

Abstract: This talk provides a review of laser pulse post-compression leveraged by the advent of the multi-pass spectral broadening scheme, including perspectives on expanding the limits of pulse duration and energy.

Y. Ma, S. Salman, C. Li, C. Mahnke, Y. Hua, J. Fellinger, A. S. Mayer, O. H. Heckl, C. Heyl, and I. Hartl
Sub-fs timing jitter of an 88 fs all-PM fiber integrated ultrafast Yb NALM oscillator
(2021)

Abstract: We demonstrate an all-PM fiber integrated femtosecond Yb NALM oscillator with 88 fs compressed pulse duration and sub-fs free-running timing jitter [25 kHz to 5 MHz].

C. Mahnke, Y. Hua, Y. Ma, S. Salman, T. Lamb, S. Schulz, C. M. Heyl, H. Cankaya, and I. Hartl
Synchronizable, low-jitter, picosecond Ho:fiber NALM oscillator for Ho:YLF amplifier driven electron acceleration
(2021)

Abstract: We demonstrate a 41.6 MHz, 1.3 ps, 140 pJ Ho:fiber oscillator centered at 2050 nm for seeding Ho:YLF amplifiers. RIN and timing jitter of the oscillator are characterized while comparing two commercial Tm pump lasers.

M. Seidel, P. Balla, G. Arisholm, L. Winkelmann, I. Hartl, and C. M. Heyl
Ultrafast Pulse Compression in Bulk with > 20 Times Spectral Broadening Factor from a Single Stage
(2021)

Abstract: We introduce the combination of multi-pass cell and multi-plate spectral broadening. We demonstrate the compression of 110-μJ pulses from 900-fs to 60-fs in a single stage and report broadening to 38-fs transform-limit by nonlinear mode-matching.

2020

A. Mayer, W. Grosinger, J. Fellinger, G. Winkler, L. Perner, S. Droste, S. Salman, C. Li, C. Heyl, I. Hartl, and O. Heckl
Flexible all-PM NALM Yb:fiber laser design for frequency comb applications: Operation regimes and their noise properties
Optics Express 28, 18946 (2020)

Abstract: We present a flexible all-polarization-maintaining (PM) mode-locked ytterbium (Yb):fiber laser based on a nonlinear amplifying loop mirror (NALM). In addition to providing detailed design considerations, we discuss the different operation regimes accessible by this versatile laser architecture and experimentally analyze five representative mode-locking states. These five states were obtained in a 78-MHz configuration at different intracavity group delay dispersion (GDD) values ranging from anomalous (-0.035 ps2) to normal (+0.015 ps2). We put a particular focus on the characterization of the intensity noise as well as the free-running linewidth of the carrier-envelope-offset (CEO) frequency as a function of the different operation regimes. We observe that operation points far from the spontaneous emission peak of Yb (~1030 nm) and close to zero intracavity dispersion can be found, where the influence of pump noise is strongly suppressed. For such an operation point, we show that a CEO linewidth of less than 10-kHz at 1 s integration can be obtained without any active stabilization.

C. Zhang, S. Schoun, C. Heyl, G. Porat, M. Gaarde, and J. Ye
Noncollinear Enhancement Cavity for Record-High Out-coupling Efficiency of an Extreme-UV Frequency Comb
Physical Review Letters 125, 093902 (2020)
Kein Abstract vorhandenLinkBibTeX
E. Appi, C. C. Papadopoulou, J. L. Mapa, N. Wesavkar, C. Jusko, P. Mosel, S. Ališauskas, T. Lang, C. M. Heyl, B. Manschwetus, M. Brachmanski, M. Braune, H. Lindenblatt, F. Trost, S. Meister, P. Schoch, R. Treusch, R. Moshammer, I. Hartl, U. Morgner, and M. Kovacev
A synchronized VUV light source based on high-order harmonic generation at FLASH
Scientific Reports 10, 6867 (2020)

Abstract: Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. The combination of these two source types was until recently not realized. The complementary properties of both sources including broad bandwidth, high pulse energy, narrowband tunability and femtosecond timing, open new opportunities for two-color pump-probe studies. Here we show first results from the commissioning of a high-harmonic beamline that is fully synchronized with the free-electron laser FLASH, installed at beamline FL26 with permanent end-station including a reaction microscope (REMI). An optical parametric amplifier synchronized with the FEL burst mode drives the HHG process. First commissioning tests including electron momentum measurements using REMI, demonstrate long-term stability of the HHG source over more than 14 hours. This realization of the combination of these light sources will open new opportunities for time-resolved studies targeting different science cases including core-level ionization dynamics or the electron dynamics during the transformation of a molecule within a chemical reaction probed on femtosecond timescales in the ultraviolet to soft X-ray spectral region.

P. Balla, A. B. Wahid, I. Sytcevich, C. Guo, A.-L. Viotti, l. Silletti, A. Cartella, S. Alisauskas, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, A. Trabattoni, B. Manschwetus, T. Lang, F. Calegari, A. Couairon, A. LHuillier, C. Arnold, I. Hartl, and C. M. Heyl
Post-compression of picosecond pulses into the few-cycle regime
Optics Letters 45, 2572 (2020)

Abstract: In this work, we demonstrate post-compression of 1.2 picosecond laser pulses to 13 fs via gas-based multipass spectral broadening. Our results yield a singlestage compression factor of about 40 at 200 W in-burst average power and a total compression factor >90 at reduced power. The employed scheme represents a route towards compact few-cycle sources driven by industrial-grade Yb:YAG lasers at high average power.

J. Fellinger, A. Mayer, W. Grosinger, G. Winkler, L. Perner, S. Droste, S. Salman, C. Li, C. Heyl, and I. Hartl
Flexible Figure-9 Yb: Fiber Laser: Operation Regimes and Noise Performance
(2020)

Abstract: We present a flexible figure-9 Yb: fiber-laser and investigate the impact of intra-cavity group delay dispersion on amplitude/phase noise. We show that the free-running carrier-envelope-offset frequency short-term linewidth can range from several MHz to <10 kHz.

P. Balla, A. B. Wahid, I. Sytcevich, C. Guo, A.-L. Viotti, L. Silletti, A. Cartella, S. Alisauskas, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, B. Manschwetus, T. Lang, A. Trabattoni, F. Calegari, A. Couairon, A. L'Huillier, C. L. Arnold, I. Hartl, and C. M. Heyl
Post-Compression of Picosecond Pulses to Four Optical Cycles via Multi-Pass Spectral Broadening
(2020)

Abstract: We demonstrate post-compression of 1.2 ps pulses to the few-cycle regime via multi-pass spectral broadening. We achieve compression factors of 40 via single and >90 via dual stage compression employing mJ pulses.

P. Balla, A. B. Wahid, I. Sytcevich, C. Guo, A.-L. Viotti, L. Silletti, A. Cartella, S. Alisauskas, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, B. Manschwetus, T. Lang, A. Trabattoni, F. Calegari, A. Couairon, A. L'Huillier, C. L. Arnold, I. Hartl, and C. M. Heyl
Post-compression of picosecond pulses to four optical cycles
(2020)

Abstract: We report post-compression of 1.2 ps pulses into the few-cycle regime via multi-pass spectral broadening. We achieve compression factors of 40 in single and 93 in a dual stage scheme using a compact setup.

E. Appi, C. Papadopoulou, J. Mapa, N. Wesavkar, C. Jusko, P. Mosel, S. Alisauskas, T. Lang, C. Heyl, and B. Manschwetus
Synchronized HHG based source at FLASH
(2020)

Abstract: We present a VUV beamline installed as pump-probe source at the free-electron laser FLASH. The source is based on high-order harmonic generation driven by femtosec-ond near-infrared laser pulses synchronized with the FEL burst mode.

M. Seidel, P. Balla, T. Binhammer, M. Frede, G. Arisholm, L. Winkelmann, I. Hartl, and C. Heyl
Hybridizing Multi-pass and Multi-plate Bulk Compression
(2020)

Abstract: With the advent of ultrafast Yb-ion based disk, slab and fibre lasers, nonlinear pulse compression methods became indispensable for the generation of high average power sub-100 fs pulses. In particular, spectral broadening in Herriott-type multi-pass cells (MPC) has been established as a novel tool for pulse compression in the 5 – 100 MW peak power range where neither solid-core fibre nor hollow-core capillaries work efficiently. The operation in the critical self-focusing regime becomes feasible through repetitive refocusing of the cell mirrors. Analogously, the multi-plate approach , which has mainly been used for broadband continuum generation, relies on the nonlinear refocusing of the Kerr media . By introducing the hybridization of both methods, we demonstrate compression factors up to 14. To the best of our knowledge this exceeds all single-stage compression factors achieved with bulk-based spectral broadening to date.

A.-L. Viotti, S. Alisauskas, P. Balla, A. Wahid, I. Sytcevich, C. Guo, L. Silletti, A. Cartella, H. Tavakol, U. Grosse-Wortmann, A. Schönberg, M. Seidel, B. Manschwetus, T. Lang, A. Trabattoni, F. Calegari, A. Couairon, A. L'Huillier, C. Arnold, I. Hartl, and C. Heyl
Post-compression of high average power picosecond pulses for few cycle generation and FEL pump-probe experiments
(2020)
Kein Abstract vorhandenLinkBibTeX
E. Appi, C. Papadopoulou, J. Mapa, N. Wesavkar, C. Jusko, P. Mosel, S. Alisauskas, T. Lang, C. Heyl, B. Manschwetus, M. Braune, M. Brachmanski, H. Lindenblatt, F. Trost, S. Meister, P. Schoch, R. Treusch, R. Moshammer, I. Hartl, U. Morgner, and M. Kovacev
A Synchronized VUV Beamline for Time Domain Two-Color Dynamic Studies at FLASH2
(2020)
Kein Abstract vorhandenLinkBibTeX
Y. Ma, S. Salman, C. Li, C. Mahnke, J. Fellinger, A. Mayer, O. Heckl, C. Heyl, and I. Hartl
Compact, Alignment-Free, Environmentally Stable Dispersion Compensated Femtosecond Yb-Fiber Oscillator
(2020)
Kein Abstract vorhandenLinkBibTeX
P. Balla, A. Wahid, I. Sytcevich, C. Guo, A. Schonberg, A.-L. Viotti, L. Silletti, A. Cartella, S. Alisauskas, H. Tavakol, U. Grosse-Wortmann, M. Seidel, B. Manschwetus, T. Lang, F. Calegari, A. Couairon, A. L'Huillier, C. Arnold, I. Hartl, and C. Heyl
Factor 40 Pulse Post-Compression of 200 W in-Burst Average Power Pulses via Single-Stage Multi-Pass Spectral Broadening
(2020)
Kein Abstract vorhandenLinkBibTeX
A. Mayer, J. Fellinger, W. Grosinger, G. Winkler, L. Perner, C. Heyl, I. Hartl, and O. Heckl
Versatile Figure-9 Design: How to Access Low-Noise Regimes in an All-PM Yb:Fiber Laser
(2020)
Kein Abstract vorhandenLinkBibTeX

2019

J. Fellinger, A. S. Mayer, G. Winkler, W. Grosinger, G.-W. Truong, S. Droste, C. Li, C. M. Heyl, I. Hartl, and O. H. Heckl
Tunable dual-comb from an all-polarization-maintaining single-cavity dual-color Yb:fiber laser
Optics Express 27, 28062 (2019)

Abstract: We demonstrate dual-comb generation from an all-polarization-maintaining dual-color ytterbium (Yb) fiber laser. Two pulse trains with center wavelengths at 1030 nm and 1060 nm respectively are generated within the same laser cavity with a repetition rate around 77 MHz. Dual-color operation is induced using a tunable mechanical spectral filter, which cuts the gain spectrum into two spectral regions that can be independently mode-locked. Spectral overlap of the two pulse trains is achieved outside the laser cavity by amplifying the 1030-nm pulses and broadening them in a nonlinear fiber. Spatially overlapping the two arms on a simple photodiode then generates a down-converted radio frequency comb. The difference in repetition rates between the two pulse trains and hence the line spacing of the down-converted comb can easily be tuned in this setup. This feature allows for a flexible adjustment of the tradeoff between non-aliasing bandwidth vs. measurement time in spectroscopy applications. Furthermore, we show that by fine-tuning the center-wavelengths of the two pulse trains, we are able to shift the down-converted frequency comb along the radio-frequency axis. The usability of this dual-comb setup is demonstrated by measuring the transmission of two different etalons while the laser is completely free-running.

K. Kovacs, B. Major, E. Balogh, C. Koros, S. P. Rudawaski, C. M. Heyl, P. Johnsson, C. L. Arnold, A. L. Hullier, V. Tosa, and K. Varju
Multi-parameter optimization of a loose focusing high flux high-harmonic beamline
Journal of Physics B: Atomic, Molecular and Optical Physics 52, 055402 (2019)

Abstract: We perform a multi-dimensional parameter scan in the generation of high-order harmonics, with the main purpose to find the macroscopic conditions that optimize the harmonic yield in a specific spectral domain, around 40 eV for this particular case. The scanned parameters are the laser pulse energy, gas pressure, interaction cell position relative to focus and the cell length, while the fixed parameters are chosen to model a loose focusing configuration which is used in many existing laboratories. We performed the simulations with a 3D non-adiabatic model complemented by a detailed analysis of the phase matching mechanisms involved in an efficient harmonic generation. Based on the results we identify a range of parameter combinations that lead to a high yield in the specified spectral domain The method and results presented here can be the framework for the design and construction of high flux high-order harmonic generation beamlines.

S. Salman, Y. Ma, K. Gürel, S. Schilt, C. Li, P. Pfäfflein, C. Mahnke, J. Fellinger, S. Droste, A. Mayer, O. Heckl, T. Südmeyer, C. Heyl, and I. Hartl
Comparison of two low-noise CEP stabilization methods for an environmentally stable Yb: fiber oscillator
(2019)

Abstract: We demonstrate a low-noise carrier-envelope-offset frequency stabilized all-PM Yb:fiber oscillator. Two different stabilization methods lead to sub 200 mrad integrated fo phase noise (10 Hz to 1 MHz), suitable for comb spectroscopy applications.

2018

C. M. Heyl, S. B. Schoun, G. Porat, H. Green, and J. Ye
A nozzle for high-density supersonic gas jets at elevated temperatures
Review of Scientific Instruments 89, 113114 (2018)

Abstract: We present the development of a gas nozzle providing high-density gas at elevated temperaturesinside a vacuum environment. Fused silica is used as the nozzle material to allow the placement ofthe nozzle tip in close proximity to an intense, high-power laser beam, while minimizing the risk ofsputtering nozzle tip material into the vacuum chamber. Elevating the gas temperature increases thegas-jet forward velocity, allowing us to replenish the gas volume in the laser-gas interaction regionbetween consecutive laser shots. The nozzle accommodates a 50μm opening hole from which asupersonic gas jet emerges. Heater wires are used to bring the nozzle temperature up to 730 °C, whilea cooling unit ensures that the nozzle mount and the glued nozzle-to-mount connection is kept at atemperature below 50 °C. The presented nozzle design is used for high-order harmonic generationin hot gases using gas backing pressures of up to 124 bars.

C. Guo, A. Harth, S. Carlstrom, Y.-C. Cheng, S. Mikaelsson, E. Marsell, C. Heyl, M. Miranda, M. Gisselbrecht, M. Gaarde, K. Schafer, A. Mikkelsen, J. Mauritsson, C. Arnold, and A. L\textquotesingle Huillier
Phase control of attosecond pulses in a train
Journal of Physics B: Atomic, Molecular and Optical Physics 51, 034006 (2018)

Abstract: Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.