880 research outputs found
Extreme Events in Resonant Radiation from Three-dimensional Light Bullets
We report measurements that show extreme events in the statistics of resonant
radiation emitted from spatiotemporal light bullets. We trace the origin of
these extreme events back to instabilities leading to steep gradients in the
temporal profile of the intense light bullet that occur during the initial
collapse dynamics. Numerical simulations reproduce the extreme valued
statistics of the resonant radiation which are found to be intrinsically linked
to the simultaneous occurrence of both temporal and spatial self-focusing
dynamics. Small fluctuations in both the input energy and in the spatial phase
curvature explain the observed extreme behaviour.Comment: 5 pages, 5 figures, submitte
Nonlinear optics of fibre event horizons
The nonlinear interaction of light in an optical fibre can mimic the physics
at an event horizon. This analogue arises when a weak probe wave is unable to
pass through an intense soliton, despite propagating at a different velocity.
To date, these dynamics have been described in the time domain in terms of a
soliton-induced refractive index barrier that modifies the velocity of the
probe. Here, we complete the physical description of fibre-optic event horizons
by presenting a full frequency-domain description in terms of cascaded
four-wave mixing between discrete single-frequency fields, and experimentally
demonstrate signature frequency shifts using continuous wave lasers. Our
description is confirmed by the remarkable agreement with experiments performed
in the continuum limit, reached using ultrafast lasers. We anticipate that
clarifying the description of fibre event horizons will significantly impact on
the description of horizon dynamics and soliton interactions in photonics and
other systems.Comment: 7 pages, 5 figure
On the statistical interpretation of optical rogue waves
Numerical simulations are used to discuss various aspects of "optical rogue
wave" statistics observed in noise-driven fiber supercontinuum generation
associated with highly incoherent spectra. In particular, we consider how long
wavelength spectral filtering influences the characteristics of the statistical
distribution of peak power, and we contrast the statistics of the spectrally
filtered SC with the statistics of both the peak power of the most red-shifted
soliton in the SC and the maximum peak power across the full temporal field
with no spectral selection. For the latter case, we show that the unfiltered
statistical distribution can still exhibit a long-tail, but the extreme-events
in this case correspond to collisions between solitons of different
frequencies. These results confirm the importance of collision dynamics in
supercontinuum generation. We also show that the collision-induced events
satisfy an extended hydrodynamic definition of "rogue wave" characteristics.Comment: Paper accepted for publication in the European Physical Journal ST,
Special Topics. Discussion and Debate: Rogue Waves - towards a unifying
concept? To appear 201
On-chip two-octave supercontinuum generation by enhancing self-steepening of optical pulses
Dramatic advances in supercontinuum generation have been made recently using
photonic crystal fibers, but it is quite challenging to obtain an
octave-spanning supercontinuum on a chip, partially because of strong
dispersion in high-index-contrast nonlinear integrated waveguides. We show by
simulation that extremely flat and low dispersion can be achieved in silicon
nitride slot waveguides over a wavelength band of 500 nm. Different from
previously reported supercontinua that were generated either by higher-order
soliton fission in anomalous dispersion regime or by self phase modulation in
normal dispersion regime, a two-octave supercontinuum from 630 to 2650 nm (360
THz in total) can be generated by greatly enhancing self-steepening in
nonlinear pulse propagation in almost zero dispersion regime, when an optical
shock as short as 3 fs is formed, which enables on-chip ultra-wide-band
applications
Modulation instability, Akhmediev Breathers and continuous wave supercontinuum generation
Numerical simulations of the onset phase of continuous wave supercontinuum
generation from modulation instability show that the structure of the field as
it develops can be interpreted in terms of the properties of Akhmediev
Breathers. Numerical and analytical results are compared with experimental
measurements of spectral broadening in photonic crystal fiber using nanosecond
pulsesComment: 22 pages, 6 figure
Theory of radiation trapping by the accelerating solitons in optical fibers
We present a theory describing trapping of the normally dispersive radiation
by the Raman solitons in optical fibers. Frequency of the radiation component
is continuously blue shifting, while the soliton is red shifting. Underlying
physics of the trapping effect is in the existence of the inertial gravity-like
force acting on light in the accelerating frame of reference. We present
analytical calculations of the rate of the opposing frequency shifts of the
soliton and trapped radiation and find it to be greater than the rate of the
red shift of the bare Raman soliton. Our findings are essential for
understanding of the continuous shift of the high frequency edge of the
supercontinuum spectra generated in photonic crystal fibers towards higher
frequencies.Comment: Several misprints in text and formulas corrected. 10 pages, 9
figures, submitted to Phys. Rev.
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