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
