A short tutorial on optical rogue waves
John M Dudley Institut FEMTO-ST CNRS-Université de Franche-Comté Besançon, France
Experiments in collaboration with the group of Guy Millot
Institut Carnot de Bourgogne (ICB) CNRS-Université de Bourgogne, Dijon, France Oceanic rogue waves
Large ocean waves that appear in an otherwise calm sea • Large (~ 30 m) surface waves
that represent statistical outliers • Measurements in 1990’s have established long-tailed statistics
1995
1945
1974
C. Kharif et al. Rogue Waves in the Ocean, Springer (2009) The 2008 scientific context
The study of oceanic rogue waves was recognized as an important field of study, requiring new research into the ways propagating wave groups on the ocean surface can attain states of high localization
Studying rogue waves in their natural environment is problematic
A 2007 Nature paper made a bold proposal that analogous effects could in fact be observed in optical fiber waveguides
The birth of nonlinear fiber optics
• Reliable techniques for fabricating small-core waveguides allows tailored linear guidance (dispersion) and controlled nonlinear interactions
The link with light – extreme nonlinear propagation The link with light – extreme nonlinear propagation
Numerical Model Stable clocks
• Low noise supercontinuum generation allows the stabilisation of the carrier oscillations underneath a femtosecond laser pulse
History of Clocks
• There is much interest in understanding these optical instabilities
Origin of the optical-ocean analogy
Deep water ocean wave groups and ultrashort envelopes in optical fibres are both described by the same propagation equation
• Ocean waves can be 1D over large scales
• Nonlinear Schrödinger equation (NLSE)
A is surface elevation of wave group
• Optical and water waves have same nonlinearity – speed depends on intensity Noisy supercontinuum spectra are also interesting
Modelling reveals that the supercontinuum can be highly unstable
Stochastic simulations
5 individual realisations, identical apart from quantum noise
Successive pulses from a laser pulse train generate significantly different spectra
We measure an artificially smooth spectrum, but the noise is still present
J. M. Dudley, G. Genty, S. Coen, Rev. Mod. Phys. 78 1135 (2006) Experiments are always better than theory …
Experiments reveal that these instabilities yield long-tailed statistics
Stochastic simulations
Time series Histogram
Power Frequency
Time Power These rare soliton events are optical rogue waves
Experiments reveal that these instabilities yield long-tailed statistics
Time series Histogram
Power Frequency
Time Power Insight from the time-frequency domain
The time-frequency domain allows convenient visualisation of complex wave envelope dynamics in optics
Spectrogram / short-time Fourier Transform
gate pulse variable delay gate
pulse
Clarification of the rogue wave mechanism
We see the emergence of localized soliton envelopes emerging from low amplitude noise on a longer input pulse
5 ps, 100 W peak power, typical supercontinuum with 1 µm zero dispersion fiber Clarification of the rogue wave mechanism
Identical parameters except for different quantum noise
5 ps, 100 W peak power, typical supercontinuum with 1 µm zero dispersion fiber Turbulence and « Champion Solitons »
We have identified important links with turbulence theory
Emergence of a champion
Collisions and turbulence in optical Rogue waves, rational solitons and rogue wave formation wave turbulence theory Phys. Lett. A 374 989-996 (2010) Phys. Lett. A 375, 3149-3155 (2011) What can we conclude? Inelastic collisions lead to the emergence of a “champion” soliton
This clarifies the origin of the supercontinuum rogue waves
Solitons can be observed on deep water but there have been no systematic observations in the natural environment
The role of this class of soliton as an ocean rogue wave candidate remains an open question
The NLSE admits other families of soliton
Solitary Waves
Pulses on a zero background
Periodic Explode-Decay Solitons or Breathers
Energy exchange between localised peaks and a background What about the “emergence” phase?
The initial phase of propagation of an optical supercontinuum shows the appearance of these localized breather states
Spontaneous Intermediate Supercontinuum MI sidebands (breather) regime Experimental confirmation of breather solutions
Analytic predictions for the spectrum are confirmed by experiments
Modulation instability, Akhmediev Breathers and continuous wave supercontinuum generation Optics Express 17, 21497 (2009)
Exciting the Peregrine Soliton
Optical technology enables experiments in “optical hydrodynamics”
Exciting the Peregrine Soliton
Optical technology enables experiments in “optical hydrodynamics”
The Peregrine soliton in nonlinear fibre optics Nature Physics 6 790 (2010)
The Peregrine soliton in a standard telecommunication fiber Optics in 2011 Optics Letters 36, 112 (2011)
Raw data
Optical technology enables experiments in “optical hydrodynamics”
The Peregrine soliton in nonlinear fibre optics Nature Physics 6 790 (2010)
The Peregrine soliton in a standard telecommunication fiber Optics in 2011 Optics Letters 36, 112 (2011)
Rogue waves can split into self-similar replicas
Experiments
Erkintalo, Genty, Kibler et al. Phys Rev Lett 107 253901 (2011) Rogue waves can split into self-similar replicas
Experiments
Confirms Sears et al Phys. Rev. Lett. 84 1902 (2000)
Erkintalo, Genty, Kibler et al. Phys Rev Lett 107 253901 (2011) Essential Conclusions
Optical fiber propagation shows noise properties qualitatively similar to those seen in the study of wave propagation on deep water
The “solitons” of the white light supercontinuum in optics may be present in deep water but there is not clear experimental evidence
The coherent structures that can be excited from specific initial conditions such as the Peregrine soliton can be seen in optics and hydrodynamics
The goals of MULTIWAVE are to explore this analogy in detail