G.J. de Valcarcel

Faraday patterns in Bose-Einstein condensates

Temporal periodic modulation of the interatomic s-wave scattering length in Bose-Einstein condensates is shown to excite subharmonic patterns in the atom density through a parametric resonance. The dominant wavelength of the spatial structures is primarily selected by the excitation frequency but also affected by the depth of the spatial modulation via a nonlinear resonance. These phenomena represent analogues of the Faraday patterns excited in vertically vibrated liquids.

Deviation from Lorenz-type dynamics of an NH3 ring laser

Abstract We show that the differences of the intensity spiral dynamics of an optically pumped NH 3 ring laser from that of the Lorenz model are caused by counterpropagating emission and by three-level coherence effects. In particular we find that under appropriate conditions the differences disappear and the laser emits purely according to the Lorenz model.

Phase dynamics in a Doppler broadened optically-pumped laser

Abstract The dynamic behavior of the phase of the generated field in a Doppler-broadened optically-pumped far-infrared laser is theoretically investigated for the first time. The phase undergoes sudden jumps of approximately π radians, which allow to establish the actual symmetry of the main attractor in the phase space, explaining the heteroclynic character of the chaotic behavior observed in experiments.

Vectorial Kerr-cavity solitons.

It is shown that a Kerr cavity with different losses for the two polarization components of the field can support both dark and bright cavity solitons (CSs). A parametrically driven Ginzburg-Landau equation is shown to describe the system for large-cavity anisotropy. In one transverse dimension the nonlinear dynamics of the bright CSs is numerically investigated.

Models, predictions, and experimental measurements of far-infrared NH3-laser dynamics and comparisons with the Lorenz-Haken model

Dynamics of the intensity and optical field amplitude of a coherently pumped far-infrared NH3-laser are measured and characterized. The experimental findings in certain parameter ranges closely follow the dynamics of the Lorenz model and its generalization for laser systems. Similarities and some specific differences are found in geometrical or statistical characterizations of the attractors. The experimental results are also consistent with the results of a model of optically pumped three-level lasers which takes into account the presence of a multiplicity of velocity groups as well as three-level coherence effects. For a certain region in parameter space, this far more complex model with a much larger phase space produces results similar to the dynamics of the Lorenz model. The model also provides explanations of differences between the experimental results and results from the Lorenz model.

Quantum squeezing of optical dissipative structures

We show that any optical dissipative structure supported by degenerate optical parametric oscillators contains a special transverse mode that is free from quantum fluctuations when measured in a balanced homodyne detection experiment. The phenomenon is not critical as it is independent of the system parameters and, in particular, of the existence of bifurcations. This result is a consequence of the spatial symmetry breaking introduced by the dissipative structure. Effects that could degrade the squeezing level are considered.

On-off intermittency in a Zeeman laser model

Abstract We numerically find on-off intermittency in a simple model for a Zeeman laser with large cavity anisotropy. The intermittency is observed in the field polarization component for large cavity losses and is induced by the chaotic dynamics of the other component. The statistical features of this behaviour are in good agreement with the theory for on-off intermittency.

Nonlinear dynamics of a class-A two-photon laser with injected signal

Abstract We performed a comprehensive study of the temporal dynamics of a two-photon laser with resonant injected signal in the high-Q cavity limit (class-A laser). The stationary solutions as well as their stability are completely characterized. In particular it is shown that tristable behaviour is possible, in contrast with two-photon optical bistability. It is also shown that there are two independent Hopf bifurcations, the sub- or supercritical character of which is analytically determined. The dynamics of the system far from the bifurcation points is classified through a numerical study.

Operation conditions and stability of a degenerate two-photon laser

Abstract The presence of a far off-resonant intermediate level in a degenerate three-level two-photon laser model manifests through a steady pump-dependent and a dynamic frequency shift on the laser equations. The steady shift strongly affects the pump threshold necessary for emission, preventing it in certain cases. The dynamic shift makes the frequency pulling/pushing to be intensity-dependent and substantially modify the domains of existence and stability of the lasing solution permitting stable operation for large cavity losses in certain cases.

Lorenz character of the Doppler-broadened far-infrared laser

The dynamic behavior of an optically pumped Doppler-broadened single-mode far-infrared laser is theoretically investigated in detail and compared with that of the simpler Lorenz–Haken laser. Through the analysis of phase diagrams, three-dimensional attractor’s projections, intensity maps, and the different terms of the laser equations, the analogies and the differences between the two models are determined. Optical pumping and Doppler broadening, present in this far-infrared laser model, can be approximately incorporated into a Lorenz–Haken model with effective parameters. These results represent a further step toward the understanding of the Lorenz-like behavior observed in recent years in the 81- and 153-μm NH3 lasers.