1,922 research outputs found
Soliton dynamics in the multiphoton plasma regime
Solitary waves have consistently captured the imagination of scientists,
ranging from fundamental breakthroughs in spectroscopy and metrology enabled by
supercontinuum light, to gap solitons for dispersionless slow-light, and
discrete spatial solitons in lattices, amongst others. Recent progress in
strong-field atomic physics include impressive demonstrations of attosecond
pulses and high-harmonic generation via photoionization of free-electrons in
gases at extreme intensities of 1014 Wcm2. Here we report the first
phase-resolved observations of femtosecond optical solitons in a semiconductor
microchip, with multiphoton ionization at picojoule energies and 1010 Wcm2
intensities. The dramatic nonlinearity leads to picojoule observations of
free-electron-induced blue-shift at 1016 cm3 carrier densities and self-chirped
femtosecond soliton acceleration. Furthermore, we evidence the time-gated
dynamics of soliton splitting on-chip, and the suppression of soliton
recurrence due to fast free-electron dynamics. These observations in the highly
dispersive slow-light media reveal a rich set of physics governing
ultralow-power nonlinear photon-plasma dynamics.Comment: 14 pages (main body and supplement), 11 figures - earlier draft;
http://www.nature.com/srep/2013/130122/srep01100/full/srep01100.htm
Laser-Plasma Interactions Enabled by Emerging Technologies
An overview from the past and an outlook for the future of fundamental
laser-plasma interactions research enabled by emerging laser systems
Dominance of backward stimulated Raman scattering in gas-filled hollow-core photonic crystal fibers
Backward stimulated Raman scattering in gases provides a promising route to
compression and amplification of a Stokes seed-pulse by counter-propagating
against a pump-pulse, as has been already demonstrated in various platforms,
mainly in free-space. However, the dynamics governing this process when seeded
by noise has not yet been investigated in a fully controllable collinear
environment. Here we report the first unambiguous observation of efficient
noise-seeded backward stimulated Raman scattering in a hydrogen-filled
hollow-core photonic crystal fiber. At high gas pressures, when the backward
Raman gain is comparable with, but lower than, the forward gain, we report
quantum conversion efficiencies exceeding 40% to the backward Stokes at 683 nm
from a narrowband 532-nm-pump. The efficiency increases to 65% when the
backward process is seeded by a small amount of back-reflected
forward-generated Stokes light. At high pump powers the backward Stokes signal,
emitted in a clean fundamental mode and spectrally pure, is unexpectedly always
stronger than its forward-propagating counterpart. We attribute this striking
observation to the unique temporal dynamics of the interacting fields, which
cause the Raman coherence (which takes the form of a moving fine-period Bragg
grating) to grow in strength towards the input end of the fiber. A good
understanding of this process, together with the rapid development of novel
anti-resonant-guiding hollow-core fibers, may lead to improved designs of
efficient gas-based Raman lasers and amplifiers operating at wavelengths from
the ultraviolet to the mid-infrared.Comment: 6 pages and 8 figures in the main section. 4 pages and 5 figures in
the supplementary sectio
Super cavity solitons and the coexistence of multiple nonlinear states in a tristable passive Kerr resonator
Passive Kerr cavities driven by coherent laser fields display a rich
landscape of nonlinear physics, including bistability, pattern formation, and
localised dissipative structures (solitons). Their conceptual simplicity has
for several decades offered an unprecedented window into nonlinear cavity
dynamics, providing insights into numerous systems and applications ranging
from all-optical memory devices to microresonator frequency combs. Yet despite
the decades of study, a recent theoretical study has surprisingly alluded to an
entirely new and unexplored paradigm in the regime where nonlinearly tilted
cavity resonances overlap with one another [T. Hansson and S. Wabnitz, J. Opt.
Soc. Am. B 32, 1259 (2015)]. We have used synchronously driven fiber ring
resonators to experimentally access this regime, and observed the rise of new
nonlinear dissipative states. Specifically, we have observed, for the first
time to the best of our knowledge, the stable coexistence of dissipative
(cavity) solitons and extended modulation instability (Turing) patterns, and
performed real time measurements that unveil the dynamics of the ensuing
nonlinear structures. When operating in the regime of continuous wave
tristability, we have further observed the coexistence of two distinct cavity
soliton states, one of which can be identified as a "super" cavity soliton as
predicted by Hansson and Wabnitz. Our experimental findings are in excellent
agreement with theoretical analyses and numerical simulations of the
infinite-dimensional Ikeda map that governs the cavity dynamics. The results
from our work reveal that experimental systems can support complex combinations
of distinct nonlinear states, and they could have practical implications to
future microresonator-based frequency comb sources.Comment: 13 pages, 6 figure
Solitary versus Shock Wave Acceleration in Laser-Plasma Interactions
The excitation of nonlinear electrostatic waves, such as shock and solitons,
by ultraintense laser interaction with overdense plasmas and related ion
acceleration are investigated by numerical simulations. Stability of solitons
and formation of shock waves is strongly dependent on the velocity distribution
of ions. Monoenergetic components in ion spectra are produced by "pulsed"
reflection from solitary waves. Possible relevance to recent experiments on
"shock acceleration" is discussed.Comment: 4 pages, 4 figure
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