The use of hollow-core photonic crystal fibers in operando spectrometry of chemical reactions is a relatively unexplored technology. It can be used in different ways and offers a variety of advantages compared with conventional operando spectrometry, such as a significantly increased path length with a simultaneously reduced volume. We apply fiber absorption spectroscopy here to the synthesis of gold nanoparticles. We measured the rate of formation of gold nanoparticles at different initial concentrations. We show that much higher resolution is possible with this technique in comparison with a conventional measurement technique using cuvettes.
A 25 THz bandwidth THz spectroscopy system exploiting BNA crystals and a tunable single-ring-fiber pulse compressor
Wei Cui,
Aswin Vishnuradhan,
Markus Lippl,
Eeswar Kumar Yalavarthi,
Angela Gamouras,
Nicolas Joly,
Jean-Michel Ménard
We present a terahertz time-domain spectroscopy (THz-TDS) system which accesses a broadband spectrum, efficiently covering the so-called "new THz gap" between 5 and 15 THz and extending beyond 25 THz. The system exploits nonlinear interactions within the organic crystal BNA (N-benzyl-2-methyl-4-nitroaniline) to generate and detect THz radiation upon excitation by a near-infrared (NIR) pulse centered at 1.03 um. To enable broadband THz spectral monitoring, the NIR pulse from a Yb-based solid-state laser undergoes spectral broadening in a gas-filled single-ring hollow-core photonic crystal fiber, followed by pulse compression to achieve durations as short as 31 fs. This approach paves the way for broadband spectroscopy in hard-to-access THz regions using widely available near-infrared ultrafast sources.
Twisted single-ring hollow-core fiber for broadband chiral detection in nanoliter volumes
Christof Helfrich,
Sonia Maniappan,
Michael Frosz,
Raju Adhikary,
Sandro Colagioia,
Nicolas Joly,
Andrea Marini,
Francesco Tani
Journal of Physics: Photonics
8
015035
(2026)
| Journal
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The ongoing evolution of hollow-core fibers continues to inspire the development of optofluidic platforms with enhanced sensitivity and minimal sample requirements. Here, we utilize the intrinsic advantages of anti-resonant reflection hollow-core fibers—such as low optical loss and broadband transmission—to realize a twisted single-ring hollow-core fiber (SR-HCF) tailored for polarization-sensitive chiral detection. We optimize the fiber geometry to ensure single-mode operation by strongly attenuating higher-order modes (>50 dB/m) while maintaining low loss for the fundamental mode (<0.1 dB/m) and reducing the sample volume to only ~660 nanoliters per 34 cm fiber length. By applying a constant twist along the fiber length, we minimize birefringence and ensure stable transmission of linear polarization states with polarization extinction ratios (PER) surpassing 38 dB. After injecting an aqueous solution of an optically active molecule, we measure its optical rotation (OR) at different wavelengths with millidegree-level sensitivity and remarkable robustness against misalignment. Measurements with different enantiomeric excess concentrations are in good agreement with independent liquid chromatography characterization.
Soliton self-frequency shift in hollow-core fiber for bright femtosecond radiation tunable across the short-wavelength infrared
Markus Lippl,
Martin Butryn,
Nicolas Joly,
Francesco Tani
We report a fiber-based source of femtosecond radiation that is spectrally tunable in the short-wavelength infrared region, delivering average powers at the multi-watt level. The system utilizes self-soliton frequency shifting in a hydrogen-filled hollow-core fiber, producing pulse trains at 1.1 MHz with integrated relative intensity noise below 0.3% and a polarization extinction ratio of 30 dB. This source constitutes an efficient and valid fiber-based alternative to optical parametric amplifiers for a variety of applications, including THz generation, multiphoton imaging, and high-harmonic generation.
Kontakt
Forschungsgruppe Nicolas Joly
Professur für Photonik Friedrich-Alexander-Universität Erlangen-Nürnberg
und
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen, Germany
