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.
early posting
Exploring the role of polarization in fiber-based quantum sources
Carla M. Brunner,
Nicolas Y. Joly
Optics Express
33
34756-34771
(2025)
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Optical fibers constitute an attractive platform for the realization of nonlinear and quantum optics processes. Here we show, through theoretical considerations, how polarization effects of both third-order parametric down-conversion and four-wave-mixing in optical fibers may be exploited to enhance detection schemes. We apply our general framework specifically to the case of tapered fibers for photon triplet generation, a long-standing goal within quantum optics, and obtain explicit expectation values for its efficiency. A quantitative investigation of four-wave-mixing in a microstructured solid-core fiber provides significant consequences for the role of polarization in experimental design.
Phase-adaptive cooling of fringe-trapped nanoparticles at room temperature in hollow-core photonic crystal fiber
Soumya Chakraborty,
Gordon Wong,
Pardeep Kumar,
Hyunjun Nam,
Claudiu Genes,
Nicolas Joly
Active feedback cooling of levitated dielectric particles is a pivotal technique for creating ultrasensitive sensors and probing fundamental physics. Here we demonstrate phase-adaptive feedback cooling of silica nanoparticles optically trapped in standing-wave potential formed by two co-linearly polarized counterpropagating diffraction-free guided modes in a hollow-core photonic crystal fiber at room temperature. Unlike standard laser intensity- or Coulomb force-based feedback, our approach modulates the relative optical phase between the counterpropagating fundamental modes proportionally to the particle's axial momentum. This generates a Stokes-like dissipative force which effectively damps the center-of-mass motion without introducing excess heating and can also work with uncharged particles. At 2 mbar air pressure, the axial center-of-mass temperature of a 195 nm silica particle is reduced by half upon application of the feedback and to 58.6 K at 0.5 mbar. The measured mechanical spectra agree well with our analytical model, validating the cooling mechanism. We envision this approach will open up pathways towards long-range, coherent control of mesoscopic particles inside hollow-core fibers, offering a fiber-integrated versatile platform for future quantum manipulation.
Velocity-modulated drag-trapping of nanoparticles by moving fringe pattern in hollow-core fiber
Soumya Chakraborty,
Gordon Wong,
Philip Russell,
Nicolas Joly
We report optical trapping and transport at atmospheric pressure of nanoparticles in a moving interference pattern in hollow-core photonic crystal fiber. Unlike in previous work at low pressure, when the viscous drag forces are weak and the particles travel at the fringe velocity, competition between trapping and drag forces causes the particle velocity to oscillate as it is momentarily captured and accelerated by each passing fringe, followed by release and deceleration by viscous forces. As a result the average particle velocity is lower than the fringe velocity. An analytical model of the resulting motion shows excellent agreement with experiment. We predict that nanoparticles can be trapped at field nodes if the fringes are rocked to and fro sinusoidally-potentially useful for reducing the exposure of sensitive particles to trapping radiation. The high precision of this new technique makes it of interest for example in characterizing nanoparticles, exploring viscous drag forces in different gases and liquids, and temperature sensing.
Prospects of phase-adaptive cooling of levitated magnetic particles in a hollow-core photonic-crystal fibre
P. Kumar,
F. G. Jimenez,
S. Chakraborty,
G. K. L. Wong,
N. Y. Joly,
C. Genes
Physical Review Research
7
023191
(2025)
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We analyze the feasibility of cooling of classical motion of a micro- to nano-sized magnetic particle, levitated inside a hollow-core photonic crystal fiber. The cooling action is implemented by means of controlling the phase of one of the counter-propagating fiber guided waves. Direct imaging of the particle's position, followed by the subsequent updating of the control laser's phase leads to Stokes type of cooling force. We provide estimates of cooling efficiency and final achievable temperature, taking into account thermal and detection noise sources. Our results bring forward an important step towards using trapped micro-magnets in sensing, testing the fundamental physics and preparing the quantum states of magnetization.
Squeezing via self-induced transparency in mercury-filled photonic crystal fibers
M. S. Najafabadi,
J. F. Corney,
L. L. Sanchez-Soto,
N. Y. Joly,
G. Leuchs
Journal of the Optical Society of America B-Optical Physics
42
749-756
(2025)
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We investigate the squeezing of ultrashort pulses using self-induced transparency in a mercury-filled hollow-core photonic crystal fiber. Our focus is on quadrature squeezing at low mercury vapor pressures, with atoms near resonance on the 3D3->63P2 transition. We vary the atomic density, and thus the gas pressure (from 2.72 to 15.7 µbar), by adjusting the temperature (from 273 to 303 K). Our results show that achieving squeezing at room temperature, considering both fermionic and bosonic mercury isotopes, requires ultrashort femtosecond pulses. We also determine the optimal detection length for squeezing at different pressures and temperatures.
Modelling spectra of hot alkali vapour in the saturation regime
Daniel Häupl,
Clare R Higgins,
Danielle Pizzey,
Jack D Briscoe,
Steven A Wrathmall,
Ifan G Hughes,
Robert Löw,
Nicolas Y. Joly
New Journal of Physics
27
033003
(2025)
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Laser spectroscopy of hot atomic vapours has been studied extensively. Theoretical models that predict the absolute value of the electric susceptibility are crucial for optimising the design of photonic devices that use hot vapours, and for extracting parameters, such as external fields, when these devices are used as sensors. To date, most of the models developed have been restricted to the weak-probe regime. However, fulfilling the weak-probe power constraint may not always be easy, desired or necessary. Here we present a model for simulating the spectra of alkali-metal vapours for a variety of experimental parameters, most distinctly at intensities beyond weak laser fields. The model incorporates optical pumping effects and transit-time broadening. We test the performance of the model by performing spectroscopy of 87Rb in a magnetic field of 0.6 T, where isolated atomic resonances can be addressed. We find very good agreement between the model and data for three different beam diameters and a variation of intensity of over five orders of magnitude. The non-overlapping absorption lines allow us to differentiate the saturation behaviour of open and closed transitions. While our model was only experimentally verified for the D2 line of rubidium, the software is also capable of simulating spectra of rubidium, sodium, potassium and caesium over both D lines.
Scientific career
Since 2021: Head of the microstructured optical fibres independent research group at the Max-Planck Institute for the Science of Light in Erlangen, Germany
Since 2009: Associate professor at the Univ. of Erlangen-Nuremberg in Germany
2005 – 2008: Maître de conférences at the Univ. of Lille in France
Education background
2012: Habilitation at the Ecole Normale Supérieure of Cachan (France) Title: Supercontinuum generation using pulses propagating in photonic crystal fibres, Defended in July. 10th 2012. Thesis adviser: Prof. Dr. Joseph Zyss.
2002-2005: Post-doctoral fellow at the University of Bath (UK) in the group of Prof. Philip Russell
1999-2002: PhD with honors (“Félicitations du jury”) at the laboratory of Physics of Lasers, Atoms, and Molecules (PhLAM) at the University of Lille (France) Title: Instabilities in pulsed mode-locked lasers: techniques for observation and control Defended on Sept. 23rd 2002. Thesis adviser: Prof. Dr. Serge Bielawski.
Awards & appointments
Since 2023: Advisor of the Erlangen Optica Student Chapter
Since 2021: Scientific coordinator of the Internation Max Planck School for the Physics of Light (IMPRS-PL)
Since 2020: Senior member of Optical Society of America (OSA)
Since 2019: Fellow of the Max Planck School of Photonics (MPSP) and member of the selection committee
Since 2016: Fellow of the Max Planck Center for Extreme and Quantum Photonics, Ottawa, Canada
1999: MENRT scholarship from the French ministry of Research to perform his doctoral degree at the University of Lille from 1999 to 2002
1998: Awarded a CIME scholarship from AUF (Agence universitaire de la Francophonie) to perform his Master study at Laval University (Québec) in 1998
Professional activities
2024: Member of the Technical Program Committee for the SPIE Photonics Europe in Strasbourg
Since 2022: Associate Editor of Opt. Express
2017: General chair of the 1st Sino-German symposium on fiber photonics for light-matter interaction in Shanghai, China
2017 – 2018: Member of the Technical Program Committee for SPIE UV and higher energy photonic
2013 – 2017: Member of Technical Program Committee for CLEO US (OSA)
2015: co-Chair of the 2nd Siegman International School of Laser (OSA)
Since 2015: Member of the Technical Program Committee for WSOF (OSA) in Hong-Kong (2015), Limasol in Cypris (2017), Adelaide in Australia (2022), and in Prague in Czech Republic (2025)
Since 20214: Member of the Student Commission of the internation Master of Advanced Optics and Technologies (MAOT)
2013: Topical session at PIERS (Progress in Electromagnetics Research Symposium) in Stockholm
2011: International conference on Nonlinear optics and complexity in photonic crystal fibers and nanostructures in Erice, in Sicily
2011: 14th International SAOT workshop on Fiber laser, sensors and materials at Reicheschwand, Germany
Since 2009: External expert for the evaluation of proposals from ANR (National agency of research in France), the Polish Society of Science, DFG (National agency of research in Germany) and ERC (European Research Council)
Since 2009: Supervisor of 13 PhD students, 2 post-docs, 14 MSc students
Ongoing projects
DFG project JO 1090/8-3 – OrbitFlySens [FAU] Orbiting flying particle sensor (with Bernhard Schmauß, FAU) – 2025-2028
BayFrance FK-34-2024 [FAU] Real-time detection of Terahertz signals using ultrashort lasers Mobility allowance – collaboration with University of Lille - 2025
BayFrance FK-35-2024 [FAU] Exploring chiral fibers for new-type of polarization-resolved endoscopy Mobility allowance – collaboration with University of Marseille – 2025
DFG project JO 1090/3-2 – Photon Triplets [FAU] Generation of photon triplets via three-photon parametric down-conversion (with Maria Chekhova) – 2024-2027
QuNet beta [MPL] 2021-2026
Max-Planck-School of Photonics (MPSP) [FAU] 2019-2025
DFG project JO 1090/6-1 -Twin Beams [FAU] Fiber source of entangled photons with giant tunable frequency separation (with Maria Chekhova) - 2021-2024
DFG project JO 1090/4-1 – Rydbergatoms in photonic crystal fibres [FAU] (with Robert Löw, University of Stuttgart) - 2019-2023
BayFrance FK-29-2018 [FAU] Frequency conversion of single-photon quantum sources using gas-filled hollow-core photonic crystal fibres Mobility allowance – collaboration with LKB, Ens Paris, France - 2018
DFG project JO 1090/3-1 – Photon Triplets [FAU] Generation of photon triplets via three-photon parametric down-conversion (with Maria Chekhova) – 2017-2020
BayFrance FK-38-2013 [FAU] Dynamical instabilities in photonic crystal fiber ring cavities synchronously pumped by femtosecond pulses Mobility allowance – collaboration with University of Lille, France - 2013-2014
