Multi-scale fibre-based optical frequency combs: science, technology and applications

Project Information

MEFISTA

Grant agreement ID: 861152

DOI

10.3030/861152

Project closed

EC signature date 10 July 2019

Start date 1 February 2020

End date 31 July 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 1 710 850,68

EU contribution

€ 1 710 850,68

Coordinated by

ASTON UNIVERSITY
United Kingdom

Periodic Reporting for period 2 - MEFISTA (Multi-scale fibre-based optical frequency combs: science, technology and applications)

Reporting period: 2022-02-01 to 2024-07-31

Summary of the context and overall objectives of the project

To respond to the huge demand for qualified experts on optical frequency combs (OFC) technologies, MEFISTA's goals were to deliver research and training to help 6 Early Stage Researchers acquire unique knowledge and research skills on OFC technology from the theory to implementation. A principal project goal was the development of novel mode-locking techniques and speciality fibres and waveguides for mode-locked femtosecond lasers (MLFLs), mid-infrared (mid-IR) tuneable dual combs sources for molecular fingerprinting, design, and characterisation of dual-comb MLFLs and MLFLs manufacturing. A point of focus was on the industrial applications related to the development and trial tests of MLFLs in the context of autonomous driving (car-object distance ranging, object recognition, moving objects speed tracing: Doppler LIDAR). Coordinated by Aston University (ASTON), UK, MEFISTA consortium boasts a consortium of world-leading academic and industrial groups working in photonics that have already significantly impacted this field. There are: i) 5 high profile academic groups, namely Aston Institute of Photonic Technologies (AIPT) at Aston University (UK); Universitat Polytecnica de Catalunya, UPC (Spain); Universite de Lille, ULille (France); Ecole polytechnique federale de Lausanne, EPFL (Switzerland) and Technical University of Denmark, DTU (Denmark); alongside ii) two industrial partners NKT PHOTONICS A/S, NKT (Denmark) and RICHMOND DESIGN & MARKETING Limited, RDM (UK).

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

MEFISTA’s six Early Stage Researchers produced 13 peer-reviewed journal papers, 2 book chapters, 5 high impact journals, 10 posters & 16 conference papers. One patent is complete and a second is in progress.

There were 22 scientific training events including 3 Transferable Skills Workshops, 2 Open to All Workshops, 4 symposia & 4 Annual Project Workshops. Over 585 external researchers attended.

Out of 23 scientific deliverables, 22 were achieved. Out of 14 scientific milestones, 13 were completed.

Listed below are MEFISTA highlights listed by work package (WP):

WP1
• Theoretical & experimental characterization of GTF in fiber ring cavities.
• Theoretical development of a model for GTF in polarization maintaining fiber cavities.
• Theoretical & experimental realization of an active cavity for GTF.
• First experimental observation of modulation instability at 2µm in a fiber ring cavity.

WP2
• Theoretical/numerical demonstration of non-Hermitian mode coupling between modes with same helicity in multimode fiber.
• Theoretical/numerical demonstration of all optical non-Hermitian mode coupling using antisymmetric modulation in 1D & 2D waveguides.
• Demonstrating non-Hermitian mode-cleaning in fiber & waveguides.
• Theoretically/numerically demonstrating non-Hermitian mode management in fiber amplifiers.

WP3
• A first demonstration of a tunable mode-locked thulium-doped fiber laser operating beyond 2µm using a CFBG as a wavelength-selective element.
• The implementation of a figure-of-9 all-fiber thulium-doped laser that generates 560fs long pulses at 1948nm wavelength. To achieve self-starting passive mode-locking, we utilized an in-fiber Faraday rotator for a nonreciprocal phase shift. This is the first all-fiber TDFL to combine an artificial saturable absorber with a chirped fiber Bragg grating (CFBG) as a wavelength-selective reflector.
• A polarization-multiplexed thulium-doped fibre laser for a free-running dual-comb generation without using optical or electronic stabilization schemes.
• The first observation of modulation instability in a coherently driven fiber resonator in the 2µm band. Active compensation of loss can be used to construct fiber ring cavities with sufficiently high finesse in the 2\,µm wavelength range to observe nonlinear effects.

WP4
• Designing a polarization-multiplexed system that generates 2 optical frequency combs with a repetition rate difference in the range of 1 KHz.
• Achieving short-term stability with a minimal drift of 1 Hz per hour & long-term stability for over 10 days in the dual-comb regime.
• Successfully using the dual-comb system for micrometre-precision distance measurements.
• Building a setup for reliable comb generation in Silicon nitride normal dispersion microresonators.
• Extending combs' lifetime by packaging the resonator & stable temperature.
• Comb frequency noise reducing by using low frequency noise lasers and an all optical feedback loop.
• Studying comb dynamics, observing a dependence of soliton properties with the pump resonance detuning.
• Generating mid infrared combs by pumping at 1970nm, single as well as multi solitons.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

MEFISTA investigated the generation of optical frequency combs (OFCs), studying models scalable to devices such as microresonators. These generate OFCs for spectroscopy, spectrometry, optical-atomic clocks & many other applications where a robust frequency reference is needed.

We have discovered novel techniques relating to the fabrication of non-Hermitian waveguides & fibers, thereby overcoming the problem of speckle formation in multimode fiber propagation by introducing longitudinal non-Hermitian potential - these findings surpass existing methods. Mode-cleaning through non-Hermitian potential in multimode fiber could hugely impact optical communications. Findings could help in designing an ultra-stable high-power mode-locked fiber laser from which frequency combs, machining & metrology could benefit.

Observed breathing dynamics are not only limited to nonlinear optics but could also benefit nonlinear physics, plasmonics, biology & materials science. The observed mechanism of the breathing emergence could be applied to the manipulation of the optical waveforms for controllable laser dynamics. The project’s results could also provide insight into large-scale, collective targeted patterns formation in engineering & biology.

The project has advanced our understanding of intensity dynamics in complex mode-locked lasers & optical frequency combs. By capturing the genesis & intensity dynamics within a dual-comb regime, we have expanded the general knowledge base in this field. We have developed a practical system for high-precision metrology applications, documented in several publications detailing how to replicate this system. This innovative tool not only allows for precise distance measurements but also holds potential for acquiring polarimetric signatures of targets, enhancing its applicability in various scientific & industrial contexts.

Another focus point was enhancing Kerr comb technology & a system enabling reliable & consistent comb generation in silicon nitride microresonators has been developed. The lifetime of combs was extended through resonator packaging and temperature stabilization measures applied to the entire device. Efforts to reduce frequency noise involved low-frequency noise lasers for pumping & the implementation of an all-optical feedback loop to mitigate thermo-refractive noise.

Exploring frequency combs post-generation has provided insights into the correlation between soliton properties & pump resonance detuning, informing future stabilization protocols. Stabilized combs with low comb line noise are useful in telecommunications. The generation of mid-infrared combs at 1970nm demonstrates an expansion in accessible wavelengths, meeting the demand for mid-IR broadband light sources in spectroscopy applications.

MEFISTA 3rd Annual Workshop, June 2023

MEFISTA Open To All Workshop, EPFL, October 2023

MEFISTA Open Access Publications - sample

MEFISTA Outreach Podcast, July 2024

MEFISTA Transferable Skills Workshop, June 2023

MEFISTA Outreach local college India, December 2022

MEFISTA Outreach on YouTube, 2023

MEFISTA Open Access Posters, 2022