Search results for " Modulation"

Incoherent modulation instability in instantaneous nonlinear Kerr media

2005

We demonstrate theoretically and experimentally in an optical fiber system that partially temporally incoherent light exhibits modulational instability during its propagation in an instantaneous response nonlinear medium. We show that the modulation frequency and gain are substantially increased with respect to the corresponding values of coherent modulational instability.

Transition from plasma-driven to Kerr-driven laser filamentation.

2011

While filaments are generally interpreted as a dynamic balance between Kerr focusing and plasma defocusing, the role of the higher-order Kerr effect (HOKE) is actively debated as a potentially dominant defocusing contribution to filament stabilization. In a pump-probe experiment supported by numerical simulations, we demonstrate the transition between two distinct filamentation regimes at 800 nm. For long pulses (1.2 ps), the plasma substantially contributes to filamentation, while this contribution vanishes for short pulses (70 fs). These results confirm the occurrence, in adequate conditions, of filamentation driven by the HOKE rather than by plasma.

Observation of induced modulational polarization instabilities and pulse-train generation in the normal-dispersion regime of a birefringent optical f…

1998

Four-photon mixing in a low-birefringence fiber is strongly influenced by the orientation of the pump and signal waves with respect to the fiber axes. We experimentally investigated the dependence of the modulational gain spectra on pump power and polarization by mixing orthogonal pump and probe light beams in a birefringent optical fiber. With a pump on the fast fiber axis, a cascade of sidebands was generated in the regime of normal fiber dispersion. These sidebands are shown to correspond to 0.2–0.3-THz trains of pulses with complex polarization profiles. The analysis reveals that, at particular values of the input pump and probe powers and signal frequency detuning, trains of dark-solit…

Experimental observation of incoherent modulation instability in standard optical fibers

2005

In this work, we demonstrate theoretically and experimentally that a partially temporally incoherent light can exhibit modulational instability when propagating in an optical fiber with instantaneous nonlinear Kerr response.

Strong four-photon conversion regime of cross-phase-modulation-induced modulational instability

2000

We investigate theoretically and experimentally the strong conversion regime of parametric four-photon amplification or induced modulational instability in the normal dispersion regime of propagation in a highly birefringent fiber. Such optical mixing is observed by injecting a tunable linearly polarized (along the fast axis) anti-Stokes signal wave copropagating with a pump equisplitted between the fiber axes (i.e., linearly polarized at 45\ifmmode^\circ\else\textdegree\fi{}) which entail that the two pump modes experience cross-phase modulation. In agreement with a four-wave model developed to study the depleted regime of the mixing process, we observe that the strongest conversion occurs…

Observation of Manakov polarization modulation instability in the normal dispersion regime of randomly birefringent telecom optical fiber

2014

Spectral broadening enhancement in silicon waveguides through pulse shaping

2012

Spectral broadening in silicon waveguides is usually inhibited at telecom wavelengths due to some adverse effects related to semiconductor dynamics, namely, two-photon and free-carrier absorption (FCA). In this Letter, our numerical simulations show that it is possible to achieve a significant enhancement in spectral broadening when we properly preshape the input pulse to reduce the impact of FCA on spectral broadening. Our analysis suggests that the use of input pulses with the correct skewness and power level is crucial for this achievemen This work was financially supported by the Plan Nacional Investigación, Desarrollo e Innovación (I+D +I) under the research project TEC2008-05490, by…

Efficient control of the energy exchange due to the Manakov vector-soliton collision

2003

By examining the concept of energy exchange among the orthogonally polarized components of each of two colliding (Manakov-like) vector solitons it is observed that a maximum or an efficient energy-exchange process is possible only for an appropriate choice of the initial physical parameters (namely, frequency separation, polarizations, time delay, and pulse-width separation between the colliding solitons) for which L(W) (walk-off length) >>L(NL) (nonlinear length). However, in this case only, the amount of energy-exchange can be considerably increased or decreased by appropriately changing the phases of colliding solitons without altering the walk-off length and the initial energy distribut…

A novel four-quadrant power supply for low-energy correction magnets

2003

Abstract This paper describes an efficient power supply to feed low-energy correction magnets in particle accelerator applications, where a controlled current with trapezoidal profile and four-quadrant operation is needed. The selected design is based on an AC–DC matrix converter topology, which uses the Space Vector Modulation (SVM) technique to obtain a near unity power factor at the AC input and output DC current regulation. This topology allows performing high-frequency isolation, while four-quadrant operation is maintained, and reducing volume and weight as compared with the classical thyristor (SCR)-based technology. Control tasks are implemented on an all-digital control card: output…

The Collinear Fast Beam laser Spectroscopy (Cfbs) experiment at Triumf

2016

Abstract Laser spectroscopy experiments at radioactive ion beam facilities around the world investigate properties of exotic nuclei for scientific endeavours such as, but not limited to, the investigation of nuclear structure. Advancements in experimental sensitivity and performance are continuously needed in order to extend the reach of nuclei that can be measured. The collinear fast beam laser spectroscopy ( Cfbs ) setup at Triumf , coupled to an out-of-plane radio-frequency quadrupole Paul trap, enables measurements of some of the most fundamental nuclear properties for long-lived ground and isomeric states. The first comprehensive overview of the Cfbs experiment is provided along with d…