Fiber-based nonlinear pulse shaping

The use of the interaction of Kerr nonlinearity with dispersion in an optical fiber has been my main focus of my research work for more than 18 years.

Through a large number of studies that were both applied or fundamental, I had the opportunity to explore the limit-free landscape of the possibilities of optical fibers. I have also been astonished to see how efficient and powerful a simple model such as the nonlinear Schrodinger equation and the very large variety of phenomena can be observed.

Optical Similaritons

main collaborators : Pr. John Dudley, Dr. Sonia Boscolo, Pr. Guy Millot

main period : 2003- on going

I have explored during my PhD the properties of optical similaritons and more specifically parabolic pulses. Those pulses emerge from the interaction of normal dispersion, Kerr nonlinearity and distributed gain and they behave as an attractor of the system, being robust against the deleterious effects of the optical wave-breaking.

I have investigated the features of parabolic similaritons mainly in Raman amplifiers at the wavelength of optical telecommunications and confirmed several of their asymptotic features. Interaction and collisions of these highly chirped structures were also studied, as well as their generation in dispersion varying fibers. We also stressed that similar profiles could be observed as transient stages of passive propagation.

Practical applications were proposed in the field of amplification, regeneration, pulse shaping and fiber lasers.

main related publications :
J.M. Dudley, C. Finot, G. Millot, D.J. Richardson, Self-similarity in ultrafast nonlinear optics, Nat. Phys., 3 (2007) 597-603.
C. Finot, J.M. Dudley, B. Kibler, D.J. Richardson, G. Millot, Optical parabolic pulse generation and applications, IEEE J. Quantum Electron., 45 (2009) 1482-1489.
C. Finot, G. Millot, C. Billet, J.M. Dudley, Experimental generation of parabolic pulses via Raman amplification in optical fiber, Opt. Express, 11 (2003) 1547-1552.
C. Finot, L. Provost, P. Petropoulos, D.J. Richardson, Parabolic pulse generation through passive nonlinear pulse reshaping in a normally dispersive two segment fiber device, Opt. Express, 15 (2007) 852-864.

Machine learning for nonlinear pulse shaping

main collaborators : Dr. Sonia Boscolo, Pr. John M. Dudley

main period : 2018-on going

Nonlinear pulse shaping can lead to pulses that can be very different in terms of pulse shapes, durations, spectral width, level of chirp. The parameter space to explore is large as the results depends on the input pulse properties (peak power, duration, level of initial chirp) as well as the fiber properties (fiber length, dispersion and nonlinear coefficient, possible distributed gain). Consequently, the design of an optimum configuration can be quite tricky and may require a large amount of numerical simulations.

We have proposed to take advantage of scaling laws of the nonlinear Schrodinger equation to reduce the complexity of the approach. We have also explored the use of machine learning with neural networks. This tool is found to be very promising to solve inverse design problem.

main related publications :

S. Boscolo, C. Finot, Artificial neural networks for nonlinear pulse shaping in optical fibers, Opt. Laser Technol., 131 (2020) 106439.
S. Boscolo, C. Finot, I. Gukov, S.K. Turitsyn, Performance analysis of dual-pump nonlinear amplifying loop mirror mode-locked all-fibre laser, Laser Phys. Lett., 16 (2019) 065105.
C. Finot, I. Gukov, K. Hammani, S. Boscolo, Nonlinear sculpturing of optical pulses with normally dispersive fiber-based devices, Opt. Fiber Technol., 45 (2018) 306-312.
S. Boscolo, J. M. Dudley, C. Finot, Modelling self-similar parabolic pulses in optical fibres with a neural network, Results in Optics, 3 (2021) 100066.

Ultrafast lasers

main collaborator : Dr. Sonia Boscolo, Dr. Junsong Peng

main period : 2008-on going

As the nonlinear evolution in fiber segment with gain is an essential stage of the dynamics of a pulse in a fiber cavity, we also got interested numerically in fiber lasers.

In close collaboration with Dr. Sonia Boscolo, we have explored several architectures including a segment of normally dispersive fiber where parabolic self-similar waveforms could emerge. We were able to stress that waveform tayloring of the pulse properties can be achieved by phase and amplitude intra-cavity shaping.

We also proposed to use the regeneration process known as Mamyshev regenerator within the cavity and to obtain a new virtual saturable absorber that can accumulate an unprecedented level of nonlinearity.

main related publications :

S. Pitois, C. Finot, L. Provost, D.J. Richardson, Generation of localized pulses from incoherent wave in optical fiber lines made of concatened Mamyshev regenerators, J. Opt. Soc. Am. B, 25 (2008) 1537-1547.
S. Boscolo, C. Finot, S.K. Turitsyn, Bandwidth Programmable Optical Nyquist Pulse Generation in Passively Mode-Locked Fiber Laser, IEEE Photon. J., 7 (2015) 1-9.
S. Boscolo, S.K. Turitsyn, C. Finot, Amplifier similariton fiber laser with nonlinear spectral compression, Opt. Lett., 37 (2012) 4531-4533.
S. Boscolo, C. Finot, H. Karakuzu, P. Petropoulos, Pulse shaping in mode-locked fiber lasers by in-cavity spectral filter, Opt. Lett., 39 (2014) 438-441.

Nonlinear spectral compression

main collaborator : Dr. Sonia Boscolo, Dr. Hervé Rigneault, Dr. Esben Andresen

main period : 2011-2017

Kerr nonlinearity in fiber leads to self-phase modulation that is often associated with a large expansion of the optical spectrum. However, when the input pulse is linearly chirped, nonlinearity can lead to a spectral narrowing and it becomes possible to focus the energy on the central frequencies without any loss of energy.

The drawback of this method is that some residual sidelobes may impair the resulting spectrum. We have proposed and experimentally demonstrated new ways to improve the quality of the spectral narrowing process based on a pulse with a temporal intensity being parabolic.

Another approach we proposed is to involve an external temporal sinusoidal phase modulation that could efficiently be viewed as a practical way to handle the consequences of self-phase modulation.

main related publications :

C. Finot, S. Boscolo, Design rules for nonlinear spectral compression in optical fibers, J. Opt. Soc. Am. B, 33 (2016) 760-767.
S. Boscolo, L.K. Mouradian, C. Finot, Enhanced nonlinear spectral compression in fibre by external sinusoidal phase modulation, J. Opt., 18 (2016) 105504.
F. Audo, S. Boscolo, J. Fatome, B. Kibler, C. Finot, Nonlinear spectrum broadening cancellation by sinusoidal phase modulation, Opt. Lett., 42 (2017) 2902-2905.
E.R. Andresen, C. Finot, D. Oron, H. Rigneault, Spectral Analog of the Gouy Phase Shift, Phys. Rev. Lett., 110 (2013) 143902.
J. Fatome, B. Kibler, E.R. Andresen, H. Rigneault, C. Finot, All-fiber spectral compression of picosecond pulses at telecommunication wavelength enhanced by amplitude shaping, Appl. Opt., 51 (2012) 4547-4553.
E.R. Andresen, J.M. Dudley, C. Finot, D. Oron, H. Rigneault, Transform-limited spectral compression by self-phase modulation of amplitude shaped pulses with negative chirp, Opt. Lett., 36 (2011) 707-709.

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