Generation of midwave- and longwave infrared few-cycle multi-mJ pulses for the study of soliton-induced ultrafast nonlinear phenomena in atomic and molecular gases by using dielectric-coated metallic hollow-core fibers

• Applicants: Dr. Uwe Griebner; Privatdozent Dr. Joachim Herrmann; Dr. Anton Husakou
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 443415906

• Final Report Year: 2024

Final Report Abstract

At first we demonstrated that a hollow-core fiber (HCF) is capable of compressing 40 mJ pulses at more than ten watts of average power at 2-µm wavelength. The pulses were compressed from 1.4 ps to 86 fs after spectral broadening in a 3-m long Kr-filled hollow-core fiber and contained more than 20 mJ energy. To generate the targeted pulses beyond 10 µm wavelength the 2-µm pumped ZGP-based midwave-IR OPCPA was extended with a longwave (LWIR) OPCPA stage. The GaSe-based LWIR OPCPA is also pumped at 2.05 µm and operates at 1 kHz repetition rate. The recompressed idler pulses at 11.4 µm have a duration of 180 fs and a record energy of 50 µJ. The pulse energy translates in a peak power of 0.3 GW and peak intensities of several TW/cm2 in the focused beam. Exciting nonlinear transmission experiments in liquid water were performed, however, to study solitonic effects beyond 10 µm in HCFs, the intensity was too low. For the first time, we have demonstrated and characterized the self-compression of pulses at 5 μm wavelength, based on propagation in an argon-filled HCF. 1.9 mJ pulses in a 1-kHz pulse train experienced a 1.8-fold compression, from 85 fs to 47 fs, which corresponds to only sub-three optical cycles. The compressed pulses contained 0.88 mJ energy resulting in a remarkable peak power of 17 GW, representing by far the highest for few-cycle pulses beyond 4 µm wavelength. The numerical simulations, in good agreement with the experiment, indicate that the compression is attributed to the solitonic self-compression regime. We numerically investigate the theoretical perspectives of solitonic self-compression for wavelengths beyond 4 µm, predicting the possibility to generate single-cycle pulses. We numerically studied the influence of the Coulomb potential on the plasma-induced susceptibility in a photoionized gas. The long-range Coulomb potential of the atomic core leads to a contribution to the imaginary part of the susceptibility which has no counterpart for a short-range potential. We demonstrate that the origin of this behavior are electrons in states very close to the continuum (nearly-free electrons). We developed a rigorous analytic approach to propagation simulation based on a propagator operator defined in the time domain. This approach enables precise simulations using short time windows even for resonant media and facilitates coupling of the propagation equation with first-principle methods; additionally, we develop a numerically efficient technique to construct such a propagator operator. Finally we demonstrated an alternative nonlinear compression scheme based on bulk materials. By post-compression of the multi-mJ 5 µm pulses using ZnSe around zero-dispersion, pulses as short as 53 fs with 1.9 mJ energy were achieved.

Publications

• Femtosecond multi-10-mJ pulses at 2 µm wavelength by compression in a hollow-core fiber. Optics Letters, 46(13), 3033.
  Nagy, Tamas; von Grafenstein, Lorenz; Ueberschaer, Dennis & Griebner, Uwe
  
• Propagator operator for pulse propagation in resonant media. Optics Express, 29(18), 29128.
  Morales, Felipe; Richter, Maria; Olvo, Vlad & Husakou, Anton
  
• 10-µJ few-cycle 12-µm source based on difference-frequency generation driven by a 1-kHz mid-wave infrared OPCPA. Optics Letters, 47(11), 2891.
  Duda, Martin; von Grafenstein, Lorenz; Bock, Martin; Ueberschaer, Dennis; Fuertjes, Pia; Roškot, Lukáš; Smrž, Martin; Novák, Ondřej & Griebner, Uwe
  
• Few-cycle 65-µJ pulses at 11.4 µm for ultrafast nonlinear longwave-infrared spectroscopy. Optica, 9(11), 1303.
  Fuertjes, Pia; Bock, Martin; von Grafenstein, Lorenz; Ueberschaer, Dennis; Griebner, Uwe & Elsaesser, Thomas
  
• High energy few-cycle pulses around 12 µm for nonlinear spectroscopy in the longwave infrared, X Ultrafast Dynamics & Ultrafast Bandgap Photonics 2023, Hersonissos, Greece, Presentation: Session X, Ultrashort Pulse-3
  U. Griebner, with P. Fuertjes, M. Bock & T. Elsaesser
  
• Ionization-induced susceptibility by nearly free electrons in gases influenced by the Coulomb potential. Physical Review A, 108(6).
  Arteaga-Sierra, F. R.; Herrmann, J. & Husakou, A.
  
• Linking high-harmonic generation and strong-field ionization in bulk crystals, X Ultrafast Dynamics & Ultrafast Bandgap Photonics 2023, Hersonissos, Greece
  Husakou, with P. Juergens, S. Roscam Abbing, M. Mero, C. Garcia, G. Brown, M. Vrakking, A. Mermillod-Blondin & P. Kraus
  
• Pulse shaping in a midwave-IR OPCPA for multi-µJ few-cycle pulse generation at 12 µm via DFG. Optics Express, 31(9), 14096.
  Bock, Martin; von Grafenstein, Lorenz; Fuertjes, Pia; Ueberschaer, Dennis; Duda, Martin; Novák, Ondřej; Abrosimov, Nikolay & Griebner, Uwe
  
• Single-stage GaSe OPCPA delivering high-energy few-cycle pulses at 11 µm wavelength, European Optical Society Annual Meeting (EOS- AM) 2023, Dijon, France
  U. Griebner with M. Bock, D. Ueberschaer & P. Fuertjes
  
• All-optical sampling of optical waveforms in solids using photoionization-induced currents, XI Ultrafast Dynamics & Ultrafast Bandgap Photonics 2024, Hersonissos, Greece
  A. Husakou, with N. Karpowicz, V. S. Yakovlev, M. Ivanov & D. A. Zimin
  
• Nonlinear compression of few-cycle multi-mJ 5 µm pulses in ZnSe around zero-dispersion. Optics Letters, 49(2), 351.
  Bock, Martin; von Grafenstein, Lorenz; Ueberschaer, Dennis; Steinmeyer, Günter & Griebner, Uwe
  
• Selfcompression of 5-μm pulses in hollow waveguides. Optics Communications, 579, 131584.
  Bock, Martin; Sapaev, Usman; Bae, Ji Eun; Husakou, Anton; Herrmann, Joachim; Nagy, Tamas & Griebner, Uwe