Ulf Peschel

Solitons of singly resonant optical parametric oscillators.

Single resonant parametric oscillators including intracavity quadratic and cubic nonlinearities are described in the mean-field limit with a cubic and quintic complex Ginzburg–Landau equation. Following our model, simple design criteria are derived for the generation of solitonlike pulses and beams for singly resonant optical parametric oscillators.

Intense pulses in air: breakup of rotational symmetry

We investigate azimuthal instabilities of intense rotationally symmetric pulsed beams propagating in air. Although the spatial-temporal evolution of the field is strongly influenced by the onset of plasma generation, the instabilities are caused chiefly by the Kerr effect. We conclude that calculations that assume rotational symmetry become unrealistic because of the fast growth of azimuthal instabilities shortly after the onset of plasma generation.

Simulation of femtosecond pulse propagation in air

We present numerical simulations of the propagation of intense spatio-temporal fields propagating in air. Characteristic parameters of the propagation like peak intensities, plasma densities and diameters of the plasma channels are obtained. The evolution of the spectral content of the pulses is investigated and, in agreement with recent experiments, white-light supercontinuum generation is observed. We show in which areas of the pulse the supercontinuum is generated and conclude that self-phase modulation is responsible for the spectral broadening. Furthermore we investigate azimuthal instabilities of intense rotationally symmetric pulsed beams propagating in air. Although the spatial-temporal evolution of the field is strongly influenced by the onset of plasma generation, the instabilities are basically caused by the Kerr effect. We conclude that calculations assuming rotational symmetry become unrealistic due to the fast growth of azimuthal instabilities in the focal region.

Discrete cavity solitons

Discrete cavity solitons are observed in arrays of coupled defects in photonic crystals or in other types of joint micro- or waveguide cavities. Various types of resting, oscillating and moving structures are found to coexist.

Dissipative Quadratic Lattice Solitons

We report for the first time on the existence of dissipative lattice solitons in a quadratically nonlinear cavity with a periodic modulation of the refractive index. We observe various localized structures, in particular multiband solitons.

A simple approach for identifying discrete cavity solitons

We introduce an analytical approach which permits to identify domains of existence in parameter space of discrete cavity solitons. We demonstrate the performance of the approach for solitons in an array of quadratically nonlinear cavities.

Birefringent quadratic solitons

We derive evolution equations for beam propagation in weakly birefringent quadratically nonlinear media. We find that an additional coupling via spatial derivatives between the field components at one frequency arises and determine various branches of soliton solutions.

Effects of spatial inhomogenities on the dynamics of cavity solitons in quadratically nonlinear media

We study the dynamics of cavity solitons due to a quadratic nonlinearity under the action of different kinds of spatial perturbations both numerically and analytically. For large scale fluctuations we find the soliton velocity to be proportional to the gradient of the respective perturbation. In case of harmonic variations of the system parameters locking on extreme values may occur. A combined action of harmonic variations and long range gradient perturbation gives rise to either locking or motion in dependence on the relation between the strength of the applied forces.

Novel 2D cavity solitons due to secondary bifurcations

Two-dimensional cavity solitons may destabilize due to secondary bifurcations. These instabilities give rise to novel localized structures as chaotically oscillating solitons with two degenerate attractors, vectorial solitons bearing also features of scalar ones and noncircular solitons.

Switching in χ (2) waveguide arrays

We show that efficient switching and routing of low power signals can be achieved in χ(2)-waveguide arrays. Signals can be transferred to different output channels and wavelengths with low cross-talk.