Low-frequency pulsations in class-B solid-state lasers with delayed feedback.

We report on the numerical observation of short-duration low-frequency pulsations in class-B solid-state lasers subject to delayed feedback. The period of these pulsations is much larger than either the delay induced by the feedback or the relaxation oscillation period of the laser without feedback. A link is established between the low-frequency pulsations and the low-frequency fluctuations observed in semiconductor lasers subject to coherent optical feedback.

Long-cavity quantum dot laser.

We propose a delay-differential equation to model dynamical instabilities in a quantum dot laser. We focus on a laser with a small gain section and a long empty section. A long cavity reduces the strong damping of the relaxation oscillation frequency.

Feedback induced instabilities in a quantum dot semiconductor laser.

We analyse the properties of GaAs based quantum dot semiconductor lasers emitting near 1310 nm. The line-width enhancement factor is shown to depend strongly on device temperature, ranging from 1.5 at 20 degrees C to 5 at 50 degrees C.

Low-frequency fluctuations in two-state quantum dot lasers.

We study the feedback-induced instabilities in a quantum dot semiconductor laser emitting in both ground and excited states. Without optical feedback the device exhibits dynamics corresponding to antiphase fluctuations between ground and excited states, while the total output power remains constant. The introduction of feedback leads to power dropouts in the ground state and intensity bursts in the excited state, resulting in a practically constant total output power.

Left-handed properties of erbium-doped crystals.

We show that lanthanide-doped crystals can be made left handed for a finite spectral range. The electronic transitions in the dopant ions are both dipolar electric and dipolar magnetic allowed. This enables tuning the permittivity and the permeability at the same frequency.

Synchronization and clustering in a multimode quantum dot laser.

We analyze experimentally the intensity oscillations of the longitudinal modes of quantum dot semiconductor lasers. We show that the modal intensities can oscillate chaotically with different average frequencies, but obey a highly organized antiphase dynamics leading to a constant total output power. The fluctuations are in the MHz range.

Electromagnetically induced left handedness in optically excited four-level atomic media.

We show that left-handed properties can be electromagnetically induced in a general four-level atomic medium for a finite spectral range. We use an electric (magnetic) atomic transition as an electric (magnetic) resonator to modify the permittivity (permeability), both at the same frequency. The implementation of the four-level model is carried out in atomic hydrogen and neon.

Bragg localized structures in a passive cavity with transverse modulation of the refractive index and the pump.

We consider a passive optical cavity containing a photonic crystal and a purely absorptive two-level medium. The cavity is driven by a superposition of two coherent beams forming a periodically modulated pump. Using a coupled mode reduction and direct numerical modeling of the full system we demonstrate the existence of bistability between uniformly periodic states, modulational instabilities and localized structures of light.

Transverse modulational instabilities of counterpropagating solitons in photorefractive crystals.

We study numerically the counterpropagating vector solitons in SBN:60 photorefractive crystals. A simple theory is provided for explaining the symmetry-breaking transverse instability of these solitons. Phase diagram is produced that depicts the transition from stable counterpropagating solitons to bidirectional waveguides to unstable optical structures.

Low-frequency fluctuations in the Lang-Kobayashi equations.

The Lang-Kobayashi equations are simplified by a local analysis that focuses, in the long-delay-time limit, on one pair of mode-antimode only. In the domain of hysteresis between the two steady states, low frequency fluctuations (LFF) can be observed if there is a domain of bistability where both steady states are unstable. The high-frequency oscillations and the drop-offs in the LFF regime are associated with a dynamics close to the unstable upper and lower branch steady states, respectively.

Body-centered cubic dissipative crystal formation in a dispersive and diffractive optical parametric oscillator.

We show that coupling diffraction and chromatic dispersion lead to body-centered cubic and hexagonally packed cylinders of dissipative optical crystals in a degenerate optical parametric oscillator. The stabilization of these crystals is a direct consequence of the interaction between the modulational and the quasi-neutral modes.

Bifurcation diagram of a complex delay-differential equation with cubic nonlinearity.

We reduce the Lang-Kobayashi equations for a semiconductor laser with external optical feedback to a single complex delay-differential equation in the long delay-time limit. The reduced equation has a time-delayed linear term and a cubic instantaneous nonlinearity. There are only two parameters, the real linewidth enhancement factor and the complex feedback strength.

Dynamical properties of lasers coupled face to face.

We derive a reduced model to describe two identical lasers coupled face to face. Two limits are introduced in the Maxwell-Bloch equations: adiabatic elimination of the material polarization and large distance between the two lasers. The resulting model describes coupled homogeneously broadened lasers, including semiconductor lasers.

Curvature instability in passive diffractive resonators.

We study the stability of localized structures in a passive optical bistable system. We show that there is a critical value of the input field intensity above which localized structures are unstable with respect to a curvature instability. Beyond this instability boundary, a transition from the localized branch of solutions to stable hexagons is found.

Two regimes of synchronization in unidirectionally coupled semiconductor lasers.

We analyze unidirectionally coupled semiconductor lasers in the feedback/injection scheme to determine their synchronization performance. As the mismatch between the two lasers increases, there is a transition from complete synchronization for identical lasers to time lag synchronization which is only partial. This corresponds to a continuous change of the global minimum that becomes a relative minimum of the synchronization error function and vice versa.