462 research outputs found
Dynamics of the transition from polarization disorder to antiphase polarization domains in vector fiber lasers
We demonstrate that nonlinear polarization coupling in a fiber ring laser without polarization selective elements,
subject to the effects of average anomalous dispersion, Kerr effect and nonlinear gain saturation, leads
to the anti-synchronization of spatio-temporal chaos into ordered laminar states of orthogonal polarization temporal
domains. Adjusting the polarization coupling may also lead to the generation of stable lattices of soliton
trains with high duty cycle at repetition rates of hundreds of MHz, as well as trains of coupled dark and bright
solitons
Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber
Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber is experimentally and numerically investigated. Guiding light in such fiber occurs via two mechanisms: photonic bandgap in the central silica core or total internal reflection in the germanium doped inclusions. By properly combining spectral filtering, dispersion tailoring and pump coupling into the fiber modes, we experimentally demonstrate efficient supercontinuum generation with controllable spectral bandwidth
Generation of unipolar pulses from nonunipolar optical pulses in a nonlinear medium
A unipolar electromagnetic pulse is a pulse with nonzero value of the static component of the Fourier spectrum of its real electric field (and not its envelope). We show how to efficiently generate unipolar pulses through propagation of an initially nonunipolar pulse in a nonlinear optical medium. One of the major results is the demonstration that the static component can only be generated in equal portions between the forward- and backward-traveling waves in the presence of nonlinear backscattering in a nonlinear medium
Wavelength conversion and temporal compression of a pulse train using a dispersion oscillating fibre
International audienceWe demonstrate the generation of a picosecond pulse train taking advantage of the cross gain occurring in a dispersion oscillating fibre. The resulting frequency-converted signal is detuned by more than 20 nm from the pump and can be temporally compressed by a factor 2 compared to the input sinusoidal pump wave
Control of near-infrared supercontinuum bandwidth by adjusting pump pulse duration
We experimentally and numerically investigated the impact of input pump pulse duration on the near-infrared bandwidth of supercontinuum generation in a photonic crystal fiber. We continuously stretched the temporal duration of the input pump laser (centered at 1030 nm) pulses from 500 fs up to 10 ps, while keeping fixed the pump peak power. We observed that the long-wavelength edge of the supercontinuum spectrum is increased by 200 nm as the pump pulse duration grows from 500 fs to 10 ps. We provide a quantitative fit of the experimental results by means of numerical simulations. Moreover, we have explained the observed spectral broadening enhancement induced by pump pulse energy by developing an approximate yet fully analytical model for soliton energy exchange through a series of collisions in the presence of stimulated Raman scattering
Understanding the United Kingdom marine aquarium tradeâa mystery shopper study of species on sale
In this study, we conducted a unique survey of marine ornamental fishes appearing in UK retail stores, as well as a review of government trade statistics, with the aim to significantly strengthen the evidenceâbase in support of future management initiatives. Fifty marine aquarium retailers were visited. A total of 380 marine aquarium fish species (4926 individuals), from 48 families were recorded with the largest proportion of individuals belonging to the families Pomacentridae, Acanthuridae, Apogonidae, Labridae, Pomacanthidae, Gobiidae and Labridae. The majority of fishes for sale (91% of species) originated from the IndoâPacific Ocean, with only a small number (9% of species) derived from the Atlantic Ocean. However, exact sources of individual species were unclear and poorly documented. Government trade statistics revealed that the ornamental reefâfish trade in the UK grew markedly between 1996 and 2008 with a rapid acceleration in 2003â2004. However, imports have declined since 2008 and amounted to less than 305,000 kg in 2017 with an economic value of UK ÂŁ3 million (c. US $3.8). Recent trade data (2017) identify Indonesia, USA, Philippines and the Maldives as the most important countries in terms of imports to the UK. The UK is an important exporter of wildâcaught fishes via transâshipment, but also production of tankâreared animals. Several species observed for sale in the UK have been designated by the IUCN and CITES as being of conservation concern, although all these animals are thought to have been captiveâreared
Spatiotemporal Characterization of Supercontinuum Extending from the Visible to the Mid-Infrared in Multimode Graded-Index Optical Fiber
We experimentally demonstrate that pumping a graded-index multimode fiber
with sub-ns pulses from a microchip Nd:YAG laser leads to spectrally flat
supercontinuum generation with a uniform bell-shaped spatial beam profile
extending from the visible to the mid-infrared at 2500\,nm. We study the
development of the supercontinuum along the multimode fiber by the cut-back
method, which permits us to analyze the competition between the Kerr-induced
geometric parametric instability and stimulated Raman scattering. We also
performed a spectrally resolved temporal analysis of the supercontinuum
emission.Comment: 5 pages 7 figure
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