Universal generation of devil's staircases near Hopf bifurcations via modulated forcing of nonlinear systems.

The discrete circle map is the archetypical example of a driven periodic system, showing a complex resonance structure under a change of the forcing frequency known as the devil's staircase. Adler's equation can be seen as the direct continuous equivalent of the circle map, describing locking effects in periodic systems with continuous forcing. This type of locking produces a single fundamental resonance tongue without higher-order resonances, and a devil's staircase is not observed.

Dynamics of on-chip asymmetrically coupled semiconductor lasers.

We investigate the dynamics of asymmetrically coupled semiconductor lasers on photonic integrated circuits in experiment and theory. The experimental observations are explained using a rate-equation model for coupled lasers incorporating a saturable coupling waveguide. We perform a bifurcation analysis of the coupled laser dynamics, focusing on the effects of the coupling phase and the dynamical difference between passive and saturable coupling waveguides.

Optical feedback induced oscillation bursts in two-state quantum-dot lasers.

We investigate the impact of short optical feedback on a two-state quantum dot laser. A region in the feedback parameter space is identified, where the laser emission periodically alternates between oscillation bursts from the quantum dot ground and excited state, i.e.

Harmonic frequency locking and tuning of comb frequency spacing through optical injection.

We show, both experimentally and theoretically, that a slave laser injected with an optical frequency comb can undergo two distinct locking mechanisms, both of which decrease the output optical comb's frequency spacing. We report that, for certain detuning and relative injection strengths, slave laser relaxation oscillations can become undamped and lock to rational frequencies of the optical comb spacing, creating extra comb tones by nonlinear dynamics of the injected laser. We also study the frequency locking of the slave laser at detunings in between the injected comb lines, which add the slave laser's frequency to the comb.

Stochastic polarization switching induced by optical injection in bimodal quantum-dot micropillar lasers.

Mutual coupling and injection locking of semiconductor lasers is of great interest in non-linear dynamics and its applications for instance in secure data communication and photonic reservoir computing. Despite its importance, it has hardly been studied in microlasers operating at μW light levels. In this context, vertically emitting quantum dot micropillar lasers are of high interest.

Class-C semiconductor lasers with time-delayed optical feedback.

We perform a linear stability analysis and numerical bifurcation diagrams of a class-C laser with time-delayed optical feedback. We employ a rate equation system based on the Maxwell-Bloch equations, and study the influence of the dephasing time on the laser dynamics. We find a stabilizing effect of an intermediate dephasing time, i.

Mutual coupling and synchronization of optically coupled quantum-dot micropillar lasers at ultra-low light levels.

Synchronization of coupled oscillators at the transition between classical physics and quantum physics has become an emerging research topic at the crossroads of nonlinear dynamics and nanophotonics. We study this unexplored field by using quantum dot microlasers as optical oscillators. Operating in the regime of cavity quantum electrodynamics (cQED) with an intracavity photon number on the order of 10 and output powers in the 100 nW range, these devices have high β-factors associated with enhanced spontaneous emission noise.

Ultra-Short Pulse Generation in a Three Section Tapered Passively Mode-Locked Quantum-Dot Semiconductor Laser.

We experimentally and theoretically investigate the pulsed emission dynamics of a three section tapered semiconductor quantum dot laser. The laser output is characterized in terms of peak power, pulse width, timing jitter and amplitude stability and a range of outstanding pulse performance is found. A cascade of dynamic operating regimes is identified and comprehensively investigated.

Tailoring the mode-switching dynamics in quantum-dot micropillar lasers via time-delayed optical feedback.

Microlasers are ideal candidates to bring the fascinating variety of nonlinear complex dynamics found in delay-coupled systems to the realm of quantum optics. Particularly attractive is the possibility of tailoring the devices' emission properties via non-invasive delayed optical coupling. However, until now scarce research has been done in this direction.

Manipulating coherence resonance in a quantum dot semiconductor laser via electrical pumping.

Excitability and coherence resonance are studied in a semiconductor quantum dot laser under short optical self-feedback. For low pump levels, these are observed close to a homoclinic bifurcation, which is in correspondence with earlier observations in quantum well lasers. However, for high pump levels, we find excitability close to a boundary crisis of a chaotic attractor.

Amplitude-phase coupling and chirp in quantum-dot lasers: influence of charge carrier scattering dynamics.

We investigate the dependence of the amplitude-phase coupling in quantum-dot (QD) lasers on the charge-carrier scattering timescales. The carrier scattering processes influence the relaxation oscillation parameters, as well as the frequency chirp, which are both important parameters when determining the modulation performance of the laser device and its reaction to optical perturbations. We find that the FM/AM response exhibits a strong dependence on the modulation frequency, which leads to a modified optical response of QD lasers when compared to conventional laser devices.

Quantum coherence induces pulse shape modification in a semiconductor optical amplifier at room temperature.

Coherence in light-matter interaction is a necessary ingredient if light is used to control the quantum state of a material system. Coherent effects are firmly associated with isolated systems kept at low temperature. The exceedingly fast dephasing in condensed matter environments, in particular at elevated temperatures, may well erase all coherent information in the material at timescales shorter than a laser excitation pulse.

Failure of the α factor in describing dynamical instabilities and chaos in quantum-dot lasers.

We show that the long-established concept of a linewidth-enhancement factor α to describe carrier-induced refractive index changes in semiconductor lasers breaks down in quantum-dot (QD) lasers when describing complex dynamic scenarios, found, for example, under high-excitation or optical injection. By comparing laser simulations using a constant α factor with results from a more complex nonequilibrium model that separately treats gain and refractive index dynamics, we examine the conditions under which an approximation of the amplitude-phase coupling by an α factor becomes invalid. The investigations show that while a quasiequilibrium approach for conventional quantum well lasers is valid over a reasonable parameter range, allowing one to introduce an α factor as a constant parameter, the concept is in general not applicable to predict QD laser dynamics due to the different time scales of the involved scattering processes.