A new tunable fiber light source synchronously pumped using fixed central wavelength pulses

A New Fiber-Based Light Source with Unique Parameters

Multicolor nonlinear imaging systems and spectrometers are advanced instruments used in medical diagnostics, biology, and chemistry to provide spatial visualization of biological or material samples. These systems require light sources offering a broad tuning range while delivering spectrally narrow, energetic pulses. Until recently, achieving such parameters necessitated bulky, expensive, and environmentally sensitive solid-state laser systems based on free-space optics. While fiber lasers providing a tunable beam with adequate power have recently emerged, Katarzyna Krupa, PhD Eng., from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, is building a novel light source designed to achieve output power and spectral resolution comparable to or exceeding current fiber lasers. Unlike existing solutions, her system relies on an oscillator operating at a fixed central wavelength. This research is conducted under the Proof of Concept action funded by the European Funds for a Modern Economy 2021–2027 (FENG) program and implemented by the Foundation for Polish Science (FNP).

"The goal of the project is to build a multicolor fiber-based light source that is spectrally tunable over a wide range, allowing the wavelength to be varied continuously from visible light to the near-infrared spectrum. Additionally, the source must deliver high-energy, picosecond, spectrally narrow pulses (approximately 1 nanometer in bandwidth). These parameters are critical for applications in nonlinear imaging systems - particularly those based on Stimulated Raman Scattering - or in spectroscopy. The core innovation lies in pumping the system with a fixed-wavelength beam using commercially available lasers. The light source under development will be tunable across the entire nonlinear gain bandwidth via four-wave mixing," explains Katarzyna Krupa, PhD Eng.

Importantly, the new light source will be compact and alignment-free. "The need for periodic alignment in free-space optics sources is inconvenient, as end-users should not be required to possess optical alignment expertise. Another advantage of our source is its robustness against environmental fluctuations, such as ambient temperature or humidity shifts, making it ideal for out-of-lab deployment. Furthermore, the all-fiber architecture provides mechanical stability - the optical output remains stable even under external physical contact," says the researcher.

The outcomes of this Proof of Concept project aim to demonstrate a functional tunable fiber source while advancing its Technology Readiness Level (TRL). A Polish patent application was filed prior to the project launch, followed by an international PCT expansion into Europe. "If European patent protection is granted, we plan to commercialize the intellectual property via licensing or patent sale to established photonics companies specializing in tunable light sources," notes Dr. Krupa.

Katarzyna Krupa, PhD Eng., obtained her doctoral degree under a joint cotutelle agreement between the University of Franche-Comté in Besançon (France) and Warsaw University of Technology. She subsequently completed a postdoctoral fellowship in nonlinear optics at the XLIM Research Institute (University of Limoges, France) before holding a research position at the Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB) at the University of Burgundy, France. She also spent a year as a Marie Skłodowska-Curie Fellow at the University of Brescia in Italy, investigating spatial and spectral dynamics in multimode optical fibers. She is currently continuing her research at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. Dr. Krupa is the co-author of over 70 scientific articles in peer-reviewed international journals and more than 140 conference proceedings. Her research focuses on nonlinear optics in optical fibers and crystals.