Efficient Raman shifting of microjoule pulses in N2-filled anti-resonant fiber
Yishai Eisenberg,
Yi-Hao Chen,
Wenchao Wang,
Francesco Tani,
Michael Frosz,
Jeffrey Moses,
Chris Xu,
Frank W. Wise
Journal of the Optical Society of America B-Optical Physics
42
2291-2295
(2025)
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We demonstrate efficient frequency down-conversion of femtosecond pulses based on the interplay of Raman-enhanced self-phase modulation and impulsive redshifting in gas-filled anti-resonant hollow-core fiber. With 20 µJ and 140 fs pulses at 1030 nm launched into a short length of fiber, pulses with durations below 100 fs are generated between 1100 and 1300 nm, with over 26% efficiency and above 5 µJ energy, for peak powers between 50 and 100 MW. The modest experimental requirements and highly efficient conversion make this a practical source for wavelength-specific applications.
Field-resolved attosecond solitons
Amelie M. Heinzerling,
Francesco Tani,
Manoram Agarwal,
Vladislav S. Yakovlev,
Ferenc Krausz,
Nicholas Karpowicz
Nature Photonics
19
772-777
(2025)
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Here we harness soliton dynamics in a hollow-core fibre to generate attosecond laser pulses spanning the deep ultraviolet (DUV) to the near infrared, and we record their electric-field waveforms using nonlinear photoconductive sampling. By combining these techniques, we measure ultrashort pulses containing a soliton at optical wavelengths and generated a resonant dispersive wave covering the DUV regime with a total pulse duration of 350 attoseconds full width at half maximum of the squared field, demonstrating the extension of the electric-field sampling bandwidth to ultrashort wavelengths. Therefore, we provide a flexible and efficient route to the generation of intense isolated attosecond pulses complementary to those based on high-harmonic generation in gases, in a spectral range particularly interesting for studies in solids and in molecules. Finally, we show that these subcycle DUV–near-infrared pulses provide sufficient intensities to ionize argon and, thus, access attosecond strong-field laser physics in these spectral regions.
Ultra-broadband UV/VIS spectroscopy enabled by resonant dispersive wave emission of a frequency comb
Adrian Kirchner,
Alexander Eber,
Lukas Fürst,
Emily Hruska,
Michael Frosz,
Francesco Tani,
Birgitta Bernhardt
Optics Express
33
7005-7015
(2025)
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We introduce an agile light source bridging from the near ultraviolet to the visible spectral region by covering more than 240 THz through resonant dispersive wave (RDW) emission in a gas-filled hollow-core fiber waveguide. The light source allows tuning of a 20 nm (FWHM) spectrum from ∼340 nm to 465 nm (645 to ∼885 THz) with conversion efficiencies of (1.5 ± 0.4) %, providing spectral powers up to (2.6 ± 1) mW/nm. This technique is showcased for spectroscopy with broadband absorption measurements of nitrogen dioxide, a molecular species of major atmospheric relevance. To our knowledge, this is the first demonstration of absorption spectroscopy with an RDW-based light source. The presented measurements indicate conservation of the coherence of the frequency comb seeding the frequency up-conversion process, paving the way towards ultra-broadband (dual) comb molecular spectroscopy across the highly relevant ultraviolet and visible range.
Giant Helical Dichroism in Twisted Hollow-Core Photonic Crystal Fibers
We show that twisted single-ring hollow-core fibers can exhibit strong helical dichroism, i.e., a different transmission depending on the orbital angular momentum of the launched light. Experimentally, we observe loss differences of at least 40 dB/m over a broad spectral range (>60 THz). We investigate the effect via analytical and numerical studies and show that considerably higher differential loss can be achieved over a broader spectral range (>180 THz). Our observation provides new routes for controlling the polarization state, extends previous studies of circularly dichroic waveguides, and has many potential applications, such as the realization of new polarizing elements in previously inaccessible spectral regions, chiral sensing, broadband generation of vortex beams, and optical communication.
Contact
Research Group Francesco Tani
Max Planck Institute for the Science of Light Staudtstr. 2 91058 Erlangen, Germany
