| 1. |
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| 2. |
- Balla, Prannay, et al.
(author)
-
Post-compression of picosecond pulses to four optical cycles
- 2020
-
In: High Intensity Lasers and High Field Phenomena, HILAS 2020. - 9781557528209
-
Conference paper (peer-reviewed)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.
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| 3. |
- Balla, Prannay, et al.
(author)
-
Postcompression of picosecond pulses into the few-cycle regime
- 2020
-
In: Optics Letters. - 0146-9592. ; 45:9, s. 2572-2575
-
Journal article (peer-reviewed)abstract
- In this work,we demonstrate postcompression of 1.2 ps laser pulses to 13 fs via gas-based multipass spectral broadening. Our results yield a single-stage 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 toward compact few-cycle sources driven by industrial-grade Yb:YAG lasers at high average power.
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| 4. |
- Brizuela, Fernando, et al.
(author)
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Efficient high order harmonic generation boosted by below threshold harmonics
- 2013
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3
-
Journal article (peer-reviewed)abstract
- High-order harmonic generation (HHG) in gases has been established as an important technique for the generation of coherent extreme ultraviolet (XUV) pulses at ultrashort time scales. Its main drawback, however, is the low conversion efficiency, setting limits for many applications, such as ultrafast coherent imaging, nonlinear processes in the XUV range, or seeded free electron lasers. Here we introduce a novel scheme based on using below-threshold harmonics, generated in a seeding cell, to boost the HHG process in a generation cell, placed further downstream in the focused laser beam. By modifying the fundamental driving field, these low-order harmonics alter the ionization step of the nonlinear HHG process. Our dual-cell scheme enhances the conversion efficiency of HHG, opening the path for the realization of robust intense attosecond XUV sources.
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| 5. |
- Carlström, Stefanos, et al.
(author)
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Spatially and spectrally resolved quantum path interference with chirped driving pulses
- 2016
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18:12
-
Journal article (peer-reviewed)abstract
- We measure spectrally and spatially resolved high-order harmonics generated in argon using chirped multi-cycle laser pulses. Using a stable, high-repetition rate laser we observe detailed interference structures in the far-field. The structures are of two kinds; off-axis interference from the long trajectory only and on-axis interference including the short and long trajectories. The former is readily visible in the far-field spectrum, modulating both the spectral and spatial profile. To access the latter, we vary the chirp of the fundamental, imparting different phases on the different trajectories, thereby changing their relative phase. Using this method together with an analytical model, we are able to explain the on-axis behaviour and access the dipole phase parameters for the short (${\alpha }_{{\rm{s}}}$) and long (${\alpha }_{{\rm{l}}}$) trajectories. The extracted results compare very well with phase parameters calculated by solving the time-dependent Schrödinger equation. Going beyond the analytical model, we are also able to successfully reproduce the off-axis interference structure.
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| 6. |
- Escoto, Esmerando, et al.
(author)
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Role of dispersion and compression ratio on the temporal contrast of SPM-broadened post-compressed pulses
- 2021
-
In: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781665418768
-
Conference paper (peer-reviewed)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.
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| 7. |
- Escoto, Esmerando, et al.
(author)
-
Temporal quality of post-compressed pulses at large compression factors
- 2022
-
In: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 39:7, s. 1694-1702
-
Journal article (peer-reviewed)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.
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| 8. |
- Guo, Chen, et al.
(author)
-
Compact 200 kHz HHG source driven by a few-cycle OPCPA
- 2017
-
In: The European Conference on Lasers and Electro-Optics, CLEO_Europe 2017. - 9781509067367 ; Part F82-CLEO_Europe 2017
-
Conference paper (peer-reviewed)abstract
- We present a compact HHG source driven by a few-cycle, few μJ, 200 kHz OPCPA system. Efficient harmonics are generated from Neon, Argon and Krypton with conversion efficiency of 4.0×10-8, 1.2×10-6 and 4.1×10-6, respectively.
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| 9. |
- Guo, Chen, et al.
(author)
-
Phase control of attosecond pulses in a train
- 2018
-
In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 51:3
-
Journal article (peer-reviewed)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.
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| 10. |
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| 11. |
- Harth, Anne, et al.
(author)
-
Compact 200 kHz HHG source driven by a few-cycle OPCPA
- 2018
-
In: Journal of Optics (United Kingdom). - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 20:1
-
Journal article (peer-reviewed)abstract
- We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ∼10-6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.
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| 12. |
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| 13. |
- Heyl, Christoph, et al.
(author)
-
High-order harmonic generation with mu J laser pulses at high repetition rates
- 2012
-
In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 45:7
-
Journal article (peer-reviewed)abstract
- We investigate the generation of high-order harmonics using laser pulse energies in the few-mu J range at high repetition rates. We analyse how the conversion efficiency is influenced by the tight focusing geometry required for the generation of high-order harmonics under these conditions. A generalized phase-matching model allows us to discuss macroscopic phase effects independent of focal length. We present experimental results using the example of a 100 kHz laser system to generate harmonics up to the 27th order in Ar with a photon flux up to 3 x 10(9) photons s(-1) into one harmonic order. High-repetition-rate femtosecond or even attosecond light sources open new possibilities for a broad range of applications such as time-resolved photoelectron spectroscopy and microscopy in the extreme ultraviolet regime.
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| 14. |
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| 15. |
- Heyl, Christoph M., et al.
(author)
-
High-energy bow tie multi-pass cells for nonlinear spectral broadening applications
- 2022
-
In: JPhys Photonics. - : IOP Publishing. - 2515-7647. ; 4:1
-
Journal article (peer-reviewed)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.
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| 16. |
- Heyl, Christoph M., et al.
(author)
-
Pulse energy scaling of multi-pass cells for nonlinear spectral broadening applications
- 2022
-
In: CLEO : Science and Innovations, S and I 2022 - Science and Innovations, S and I 2022. - 9781557528209
-
Conference paper (peer-reviewed)abstract
- We discuss basic pulse energy scaling principles for multi-pass cells (MPCs) and introduce a novel multi-pass cell type which we employ to numerically predictpost-compression of 125 mJ pulses using a 2 m setup.
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| 17. |
- Heyl, Christoph, et al.
(author)
-
Macroscopic effects in noncollinear high-order harmonic generation.
- 2014
-
In: Physical Review Letters. - 1079-7114. ; 112:14
-
Journal article (peer-reviewed)abstract
- We study two-color high-order harmonic generation using an intense driving field and its weak second harmonic, crossed under a small angle in the focus. Employing sum- and difference-frequency generation processes, such a noncollinear scheme can be used to measure and control macroscopic phase matching effects by utilizing a geometrical phase mismatch component, which depends on the noncollinear angle. We further show how spatial phase effects in the generation volume are mapped out into the far field allowing a direct analogy with temporal carrier envelope effects in attosecond pulse generation.
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| 18. |
- Heyl, Christoph, et al.
(author)
-
Noncollinear optical gating
- 2014
-
In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16
-
Journal article (peer-reviewed)abstract
- We present a novel scheme for high-order harmonic generation, enabling the production of spatially separated isolated attosecond pulses. This can be achieved by driving the generation process with two identical, but temporally delayed laser pulses, which are noncollinearly overlapping in the generation medium. Our approach provides intense attosecond pulses directly separated from the fundamental field, which is left undistorted. The method is therefore ideally suited for pump-probe studies in the extreme ultraviolet regime and promises new advances for intra-cavity attosecond pulse generation. We present a theoretical description of noncollinear optical gating, with an analytical derivation and simulations using the strong field approximation.
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| 19. |
- Heyl, Christoph
(author)
-
Scaling and Gating Attosecond Pulse Generation
- 2014
-
Doctoral thesis (other academic/artistic)abstract
- High-order harmonic generation (HHG) provides the basis for attosecond light sources delivering coherent pulses in the extreme ultraviolet spectral region. Such light sources are employed for a variety of applications within imaging, attosecond spectroscopy, and high-precision frequency metrology. However, the rather low efficiency of the HHG process, which implies a limited pulse energy and repetition rate, places restrictions on many applications. In this thesis, the scaling of different parameters controlling the generation conditions for HHG in gases is analyzed. A general scaling model is developed, which allows scaling of the pulse energy and repetition rate of attosecond sources over many orders of magnitude, while maintaining temporal and spatial pulse characteristics. The scaling model is applied to different attosecond beam lines, which were developed and built as part of this thesis work. This includes a high-repetition rate (200\,kHz) beam line used for photoelectron emission microscopy applications, and an intense harmonic beam line delivering pulses with up to 3 µJ in the extreme ultraviolet, which was used for coherent imaging as well as for nonlinear spectroscopy applications. In addition, microscopic sub-cycle control mechanisms based on multi-color field synthesis are studied, as well as noncollinear generation geometries. It is shown that a noncollinear geometry can be used to angularly streak attosecond pulse trains, allowing access to single pulses within the train. This technique is of interest for attosecond pump-probe measurements as well as for isolated attosecond pulse generation inside an optical cavity, a scheme that promises attosecond pulses at unprecedented power levels and repetition rates.
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| 20. |
- Heyl, Christoph, et al.
(author)
-
Spectrally Resolved Maker Fringes in High-Order Harmonic Generation
- 2011
-
In: Physical Review Letters. - 1079-7114. ; 107:3
-
Journal article (peer-reviewed)abstract
- We investigate macroscopic interference effects in high-order harmonic generation using a Ti:sapphire laser operating at a 100 kHz repetition rate. The structure and behavior of spectral and spatial interference fringes are explained and analytically described by transient phase matching of the long electron trajectory contribution. Time-frequency mapping due to the temporal chirp of the harmonic emission allows us to observe Maker fringes directly in the spectral domain.
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| 21. |
- Jarnac, Amelie, et al.
(author)
-
Compression of TW class laser pulses in a planar hollow waveguide for applications in strong-field physics
- 2014
-
In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 68:12
-
Journal article (peer-reviewed)abstract
- We demonstrate pulse post-compression of a TW class chirped pulse amplification laser employing a gas-filled planar hollow waveguide. A waveguide throughput of 80% is achieved for 50 mJ input pulse energy. Good focusability is found and after compression with chirped mirrors a pulse duration of sub-15 fs is measured in the beam center. Whereas a total energy efficiency of approximate to 70% should be achievable, our post-compressor currently delivers 20 mJ output pulse energy (approximate to 40% efficiency), mostly limited by apertures of chirped mirrors and vacuum windows. The viability of the planar hollow waveguide compression scheme for applications in strong-field physics is demonstrated by generating high-order harmonics in a pulsed Ar gas cell.
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| 22. |
- Kroon, David, et al.
(author)
-
Attosecond pulse walk-off in high-order harmonic generation
- 2014
-
In: Optics Letters. - 0146-9592. ; 39:7, s. 2218-2221
-
Journal article (peer-reviewed)abstract
- We study the influence of the generation conditions on the group delay of attosecond pulses in high-order harmonic generation in gases. The group delay relative to the fundamental field is found to decrease with increasing gas pressure in the generation cell, reflecting a temporal walk-off due to the dispersive properties of the nonlinear medium. This effect is well reproduced using an on-axis phase-matching model of high-order harmonic generation in an absorbing gas. (C) 2014 Optical Society of America
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| 23. |
- Kühn, Sergei, et al.
(author)
-
The ELI-ALPS facility : The next generation of attosecond sources
- 2017
-
In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:13
-
Research review (peer-reviewed)abstract
- This review presents the technological infrastructure that will be available at the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) international facility. ELI-ALPS will offer to the international scientific community ultrashort pulses in the femtosecond and attosecond domain for time-resolved investigations with unprecedented levels of high quality characteristics. The laser sources and the attosecond beamlines available at the facility will make attosecond technology accessible for scientists lacking access to these novel tools. Time-resolved investigation of systems of increasing complexity is envisaged using the end stations that will be provided at the facility.
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| 24. |
- Larsen, Esben Witting, et al.
(author)
-
Sub-cycle ionization dynamics revealed by trajectory resolved, elliptically-driven high-order harmonic generation
- 2016
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Journal article (peer-reviewed)abstract
- The sub-cycle dynamics of electrons driven by strong laser fields is central to the emerging field of attosecond science. We demonstrate how the dynamics can be probed through high-order harmonic generation, where different trajectories leading to the same harmonic order are initiated at different times, thereby probing different field strengths. We find large differences between the trajectories with respect to both their sensitivity to driving field ellipticity and resonant enhancement. To accurately describe the ellipticity dependence of the long trajectory harmonics we must include a sub-cycle change of the initial velocity distribution of the electron and its excursion time. The resonant enhancement is observed only for the long trajectory contribution of a particular harmonic when a window resonance in argon, which is off-resonant in the field-free case, is shifted into resonance due to a large dynamic Stark shift.
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| 25. |
- Lorek, Eleonora, et al.
(author)
-
High-order harmonic generation using a high-repetition-rate turnkey laser.
- 2014
-
In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 85:12
-
Journal article (peer-reviewed)abstract
- We generate high-order harmonics at high pulse repetition rates using a turnkey laser. High-order harmonics at 400 kHz are observed when argon is used as target gas. In neon, we achieve generation of photons with energies exceeding 90 eV (∼13 nm) at 20 kHz. We measure a photon flux of up to 4.4 × 10(10) photons per second per harmonic in argon at 100 kHz. Many experiments employing high-order harmonics would benefit from higher repetition rates, and the user-friendly operation opens up for applications of coherent extreme ultra-violet pulses in new research areas.
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| 26. |
- Louisy, Maite, et al.
(author)
-
Gating attosecond pulses in a noncollinear geometry
- 2015
-
In: Optica. - 2334-2536. ; 2:6, s. 563-566
-
Journal article (peer-reviewed)abstract
- The efficient generation of isolated attosecond pulses (IAPs), giving access to ultrafast electron dynamics in various systems, is a key challenge in attosecond science. IAPs can be produced by confining the extreme ultraviolet emission generated by an intense laser pulse to a single field half-cycle or, as shown recently, by employing angular streaking methods. Here, we experimentally demonstrate the angular streaking of attosecond pulse trains in a noncollinear geometry, leading to the emission of angularly separated IAPs. The noncollinear geometry simplifies the separation of the fundamental laser field and the generated pulses, making this scheme promising for intracavity attosecond pulse generation, thus opening new possibilities for high-repetition-rate attosecond sources. (C) 2015 Optical Society of America
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| 27. |
- Maclot, Sylvain, et al.
(author)
-
Towards XUV-pump XUV-probe experiments with attosecond pulses at the Lund Laser Centre
- 2015
-
In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635, s. 112079-112079
-
Conference paper (peer-reviewed)abstract
- The relaxation dynamics of an ionized/excited molecular system leads to different fundamental processes occurring at sub-femtosecond timescales. Time-resolved XUV-pump XUV-probe experiments should allow deeper insight to the key roles of these processes. Such studies should be feasible soon thanks to experimental schemes similar to those at the high-intensity high-order harmonic generation beamline at the Lund Laser Centre.
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| 28. |
- Mikaelsson, Sara, et al.
(author)
-
Spatio-temporal characterization and optimization of a 200-kHz OPCPA laser system
- 2018
-
In: CLEO : Science and Innovations, CLEO_SI 2018 - Science and Innovations, CLEO_SI 2018. - 9781557528209 ; Part F94-CLEO_SI 2018
-
Conference paper (peer-reviewed)abstract
- We present measurements on a few cycle OPCPA laser chain where due to careful characterization and compensation of the spectral phase and spatio-temporal couplings, we are able achieve efficient HHG with very low pulse energy.
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| 29. |
- Porat, Gil, et al.
(author)
-
Phase-matched extreme-ultraviolet frequency-comb generation
- 2018
-
In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 12:7, s. 387-391
-
Journal article (peer-reviewed)abstract
- Laser-driven high-order harmonic generation1,2 provides spatially3 and temporally4 coherent tabletop sources of broadband extreme-ultraviolet (XUV) light. These sources typically operate at low repetition rates, frep ≲ 100 kHz, where phase-matched HHG is readily achieved5,6. However, many applications demand the improved counting statistics or frequency-comb precision afforded by high repetition rates, frep > 10 MHz. Unfortunately, at such high frep, phase matching is prevented by steady-state plasma accumulated in the generation volume7–11, strongly limiting the XUV average power. Here, we use high-temperature gas mixtures as the generation medium to increase the gas translational velocity, thereby reducing the steady-state plasma in the laser focus. This allows phase-matched XUV emission inside a femtosecond enhancement cavity at frep = 77 MHz, enabling a record generated power of ~ 2 mW in a single harmonic order. This power scaling opens up many demanding applications, including XUV frequency-comb spectroscopy12,13 of few-electron atoms and ions for precision tests of fundamental physical laws and constants14–20.
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| 30. |
- Rajhans, Supriya, et al.
(author)
-
Post-compression of multi-millijoule picosecond pulses to few-cycles approaching the terawatt regime
- 2023
-
In: Optics Letters. - 0146-9592. ; 48:18, s. 4753-4756
-
Journal article (peer-reviewed)abstract
- Advancing ultrafast high-repetition-rate lasers to shortest pulse durations comprising only a few optical cycles while pushing their energy into the multi-millijoule regime opens a route toward terawatt-class peak powers at unprecedented average power. We explore this route via efficient post-compression of high-energy 1.2 ps pulses from an ytterbium InnoSlab laser to 9.6 fs duration using gas-filled multi-pass cells (MPCs) at a repetition rate of 1 kHz. Employing dual-stage compression with a second MPC stage supporting a close-to-octave-spanning bandwidth enabled by dispersion-matched dielectric mirrors, a record compression factor of 125 is reached at 70% overall efficiency, delivering 6.7 mJ pulses with a peak power of ∼0.3 TW. Moreover, we show that post-compression can improve the temporal contrast at multi-picosecond delay by at least one order of magnitude. Our results demonstrate efficient conversion of multi-millijoule picosecond lasers to high-peak-power few-cycle sources, prospectively opening up new parameter regimes for laser plasma physics, high energy physics, biomedicine, and attosecond science.
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| 31. |
- Reid, Derryck T., et al.
(author)
-
Roadmap on ultrafast optics
- 2016
-
In: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 18:9
-
Journal article (peer-reviewed)abstract
- The year 2015 marked the 25th anniversary of modern ultrafast optics, since the demonstration of the first Kerr lens modelocked Ti:sapphire laser in 1990 (Spence et al 1990 Conf. on Lasers and Electro-Optics, CLEO, pp 619-20) heralded an explosion of scientific and engineering innovation. The impact of this disruptive technology extended well beyond the previous discipline boundaries of lasers, reaching into biology labs, manufacturing facilities, and even consumer healthcare and electronics. In recognition of such a milestone, this roadmap on Ultrafast Optics draws together articles from some of the key opinion leaders in the field to provide a freeze-frame of the state-of-the-art, while also attempting to forecast the technical and scientific paradigms which will define the field over the next 25 years. While no roadmap can be fully comprehensive, the thirteen articles here reflect the most exciting technical opportunities presented at the current time in Ultrafast Optics. Several articles examine the future landscape for ultrafast light sources, from practical solid-state/fiber lasers and Raman microresonators to exotic attosecond extreme ultraviolet and possibly even zeptosecond x-ray pulses. Others address the control and measurement challenges, requiring radical approaches to harness nonlinear effects such as filamentation and parametric generation, coupled with the question of how to most accurately characterise the field of ultrafast pulses simultaneously in space and time. Applications of ultrafast sources in materials processing, spectroscopy and time-resolved chemistry are also discussed, highlighting the improvements in performance possible by using lasers of higher peak power and repetition rate, or by exploiting the phase stability of emerging new frequency comb sources.
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| 32. |
- Rudawski, Piotr, et al.
(author)
-
A high-flux high-order harmonic source.
- 2013
-
In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 84:7
-
Journal article (peer-reviewed)abstract
- We develop and implement an experimental strategy for the generation of high-energy high-order harmonics (HHG) in gases for studies of nonlinear processes in the soft x-ray region. We generate high-order harmonics by focusing a high energy Ti:Sapphire laser into a gas cell filled with argon or neon. The energy per pulse is optimized by an automated control of the multiple parameters that influence the generation process. This optimization procedure allows us to obtain energies per pulse and harmonic order as high as 200 nJ in argon and 20 nJ in neon, with good spatial properties, using a loose focusing geometry (f#≈400) and a 20 mm long medium. We also theoretically examine the macroscopic conditions for absorption-limited conversion efficiency and optimization of the HHG pulse energy for high-energy laser systems.
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| 33. |
- Rudawski, Piotr, et al.
(author)
-
Carrier-envelope phase dependent high-order harmonic generation with a high-repetition rate OPCPA-system
- 2015
-
In: European Physical Journal D. Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060. ; 69:3
-
Journal article (peer-reviewed)abstract
- We study high-order harmonic generation with a high-repetition rate (200 kHz), few-cycle, driving laser, based on optical parametric chirped pulse amplification. The system delivers carrier-envelope phase stable, 8 fs, 10 mu J pulses at a central wavelength of 890 nm. High-order harmonics, generated in a high-pressure Ar gas jet, exhibit a strong CEP-dependence over a large spectral range owing to excellent stability of the driving laser pulses. This range can be divided into three spectral regions with distinct CEP influence. The observed spectral interference structures are explained by an analytical model based upon multiple pulse interferences.
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| 34. |
- Schwenke, Jörg, et al.
(author)
-
Digital in-line holography on amplitude and phase objects prepared with electron beam lithography.
- 2012
-
In: Journal of Microscopy. - : Wiley. - 0022-2720. ; 247:2, s. 196-201
-
Journal article (peer-reviewed)abstract
- We report on the fabrication and characterization of amplitude and phase samples consisting of well defined Au or Al features formed on ultrathin silicon nitride membranes. The samples were manufactured using electron beam lithography, metallization and a lift-off technique, which allow precise lateral control and thickness of the metal features. The fabricated specimens were evaluated by conventional microscopy, atomic force microscopy and with the digital in-line holography set-up at the Lund Laser Centre. The latter uses high-order harmonic generation as a light source, and is capable of recovering both the shape and phase shifting properties of the samples. We report on the details of the sample production and on the imaging tests with the holography set-up.
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| 35. |
- Schönberg, Arthur, et al.
(author)
-
Energy-Scaling of Multi-Pass Cell Post-Compression : The Bow Tie MPC Scheme
- 2022
-
In: Proceedings of the 2022 Conference on Lasers and Electro-Optics Pacific Rim.
-
Conference paper (peer-reviewed)abstract
- We introduce the bow tie multi-pass cell as a new scheme for post-compression of high-energy laser pulses, overcoming current limits of Herriott-type multi-pass cell-based post-compression imposed mainly by mirror damage threshold limitations.
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| 36. |
- Viotti, Anne Lise, et al.
(author)
-
60 fs, 1030 nm FEL pump-probe laser based on a multi-pass post-compressed Yb:YAG source
- 2021
-
In: Journal of Synchrotron Radiation. - 0909-0495. ; 28, s. 36-43
-
Journal article (peer-reviewed)abstract
- This paper reports on nonlinear spectral broadening of 1.1 ps pulses in a gas-filled multi-pass cell to generate sub-100 fs optical pulses at 1030 nm and 515 nm at pulse energies of 0.8 mJ and 225 μJ, respectively, for pump-probe experiments at the free-electron laser FLASH. Combining a 100 kHz Yb:YAG laser with 180 W 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.
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| 37. |
- Viotti, Anne Lise, et al.
(author)
-
Few-cycle pulse generation by double-stage hybrid multi-pass multi-plate nonlinear pulse compression
- 2023
-
In: Optics Letters. - 0146-9592. ; 48:4, s. 984-987
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Journal article (peer-reviewed)abstract
- Few-cycle pulses present an essential tool to track ultrafast dynamics in matter and drive strong field effects. To address photon-hungry applications, high average power lasers are used which, however, cannot directly provide sub-100-fs pulse durations. Post-compression of laser pulses by spectral broadening and dispersion compensation is the most efficient method to overcome this limitation. We present a notably compact setup which turns a 0.1-GW peak power, picosecond burst-mode laser into a 2.9-GW peak power, 8.2-fs source. The 120-fold pulse duration shortening is accomplished in a two-stage hybrid multi-pass, multi-plate compression setup. To our knowledge, neither shorter pulses nor higher peak powers have been reported to-date from bulk multi-pass cells alone, manifesting the power of the hybrid approach. It puts, for instance, compact, cost-efficient, and high repetition rate attosecond sources within reach.
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| 38. |
- Viotti, Anne Lise, et al.
(author)
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Intra-Burst Pulse Characterization of a High-Power Post-Compressed Yb:YAG Laser at 100 kHz Repetition Rate
- 2021
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In: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - 9781665418768
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Conference paper (peer-reviewed)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).
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| 39. |
- Viotti, Anne Lise, et al.
(author)
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Intra-burst temporal pulse contrast of a high-power post-compressed picosecond Yb:YAG laser
- 2021
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In: Conference on Laser and Electro-Optics : Science and Innovations, CLEO:S and I 2021 - Science and Innovations, CLEO:S and I 2021. - 9781557528209
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Conference paper (peer-reviewed)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.
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| 40. |
- Viotti, Anne Lise, et al.
(author)
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Multi-pass cells for post-compression of ultrashort laser pulses
- 2022
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In: Optica. - 2334-2536. ; 9:2, s. 197-216
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Journal article (peer-reviewed)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.Amuch more powerefficient 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.
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| 41. |
- Viotti, Anne Lise, et al.
(author)
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Temporal pulse quality of a Yb:YAG burst-mode laser post-compressed in a multi-pass cell
- 2021
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In: Optics Letters. - 0146-9592. ; 46:18, s. 4686-4689
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Journal article (peer-reviewed)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.
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