A set of rate equations is derived describing the deterministic multi-mode dynamics of a semiconductor laser. Mutual interactions among the lasing modes, induced by high-frequency modulations of the carrier distribution, are described by carrier-inversion moments and lead to special spectral content of each spatial mode. The diffusion of carriers is shown to play an important role in determining the spectral properties of the field. The Bogatov effect of asymmetric gain suppression in semiconductor lasers will be derived. We will explicitly discuss the nontrivial relationship between the modes of the nonlinear cavity and the optical spectrum of the laser output and illustrate this for a two and three-mode laser.
Vertical Cavity Surface Emitting Lasers (VCSELs) often present switching between two orthogonal polarization states when varying parameters like e.g. current or temperature. Around such a switching point, the system randomly jumps between these two polarization states (mode hopping), driven by noise. In this contribution, we present experimental and numerical results showing the effect of coloured noise, externally added to the current, on the switching characteristics of a VCSEL.
A method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were two routes to chaos are implicated. Finally, we confirm the calculations by showing an avoided crossing type of behavior for the coupling strength.
Low Frequency Fluctuations (LFF) are defined by an abrupt (1 ns)
drop-out of the emitted power followed by a gradual (50 ns)
build-up of the power until the next drop-out event, when the
laser with feedback is biased close to threshold. In this paper
experimental and theoretical results on a vertical-cavity
surface-emitting laser (VCSEL) with polarized optical feedback are
presented. Experimentally, we observe single-mode low frequency
dynamics when the VCSEL is biased below the solitary laser
threshold. We can choose one of the two typical polarization modes
(PM) of the VCSEL to be lasing, by an adequate choice of the
polarization direction in the external cavity. Our theoretical
analysis is based on a model developed by Loiko et al. which is an
extension of the Spin-Flip model. We confirm the appearance of
single-mode LFF and also reproduce the response of the orthogonal
polarization mode above the solitary laser threshold, both
deterministically and in presence of noise. This analysis shows
that aiming the feedback at the passive mode (in absence of
feedback) forces the active mode to react with short pulses, due
to parasitic carrier theft, while targeting the feedback at the
active mode induces a smaller response from the orthogonal
polarization mode. This difference in response allows us to
conclude that the secondary polarization does not play an
essential role in the LFF dynamics.
Semiconductor lasers subject to filtered feedback are examined in the limit of a narrow filter. Under particular conditions, the laser dynamical equations reduce to the equations of a laser subject to an externally injected signal. The conditions for steady state locking and Hopf bifurcation can be determined analytically allowing a deeper understanding of the role of the laser parameters on the perturbed semiconductor laser dynamics. The success of our analysis motivates the study of other feedback cases such as the laser subject to slow phase-conjugated feedback.
We find that, although inversion noise has only a marginal effect on the linewidth of a semiconductor laser in CW operation, in the presence of dynamics it may play a key role in determining the final dynamical state. It is therefore essential to include both field noise and carrier noise of realistic strength when analysing semiconductor laser dynamics. Next we investigate the influence of quantum noise, both field and carrier noise, on the highly complex nonlinear dynamics that arise in a single-mode semiconductor laser subject to filtered optical feedback. Our numerical study based on stochastic rate equations shows that for a wide range of filter widths the noise may lead to qualitatively different dynamics than predicted by a deterministic analysis. In particular, we find that certain attractors that are predicted in the absence of noise may no longer be available when the effects of noise are correctly incorporated, while others show remarkable robustness instead. In general, the results confirm that carrier noise in the laser can influence the dynamics quite substantially. Finally, we present numerical results of noise-induced pulsations in a semiconductor laser with optical injection. We show that, close to the locking edge, patterns of single, two and three pulses can be excited and we suggest that experimental study of this multi-pulse excitability be based on pulse timing statistics.
A novel multi-longitudinal-mode rate-equations description of the Fabry-Perot type semiconductor laser is presented. The model includes gain dynamics among the longitudinal modes due to e.g. spatial hole burning.
A multimode model is necessary to describe the behavior observed in
a twin stripe diode laser. We will use a single-stripe version of the
device to calibrate the parameters enabling the model to be used in
the description and analysis of the twin-stripe lasers.
Our report focuses on the strong kink found in the P-I output of an asymmetric twin stripe semiconductor laser. A multi longitudinal mode model is used to describe the system. The model allows for asymmetric coupling of the two lasers and also accounts for multi longitudinal effects within and in-between the lasers.
Through simulations based on the rate equations for diode lasers with filtered optical feedback, we show that in the Coherence Collapse regime a large variety of dynamics is predicted such as periodic and quasiperiodic oscillations and chaos. The control of the transition through these dynamical regimes is achieved through the filter parameters : the filter's spectral width and its central frequency.
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