Coupled Semiconductor Laser Arrays Research Articles

Extreme events in two laterally-coupled semiconductor lasers.

Rogue waves (RWs) are extreme and rare waves that emerge unexpectedly in many natural systems and their formation mechanism and prediction have been extensively studied. Here, we numerically demonstrate the appearance of extreme events (EEs) for the first time, to the best of our knowledge, in the chaotic regimes of a two-element coupled semiconductor laser array. Based on coupled-mode theory, we characterize the occurrence of EEs by calculating the probability distribution, which confirms the RW-type feature of the intensity pulses, i.e., non-Gaussian distribution. Combining with the results of the 0-1 test for chaos, we confirm that EEs originate from deterministic nonlinearities in coupled semiconductor laser systems. We show that EEs can be predicted with a long anticipation time. Furthermore, simulation results manifest that the occurrence probability of EEs can be flexibly tuned by tailoring the coupling parameter space. With the help of two-dimension maps, the effects of key parameters, i.e., the waveguide structure and the pump level, on the formation of EEs are discussed systematically. This work provides a new platform for the research of EEs in a highly integrated structure and opens up a novel investigation field for coupled semiconductor laser arrays.

Evanescently Coupled DBR Laser Arrays in the 760–770 nm Wavelength Range

In this letter, we present evanescently coupled semiconductor laser arrays designed with a distributed Bragg reflector section for spectrally narrow emission and a combined waveguide section for high optical output powers. These devices were designed and fabricated in the AlGaAs material system with an InGaAsP quantum well providing emission in the 760–770 nm wavelength range. Measurements of the light-current characteristics reveal high optical output powers of 600 mW at 20 °C and 700 mW at 5 °C limited by thermal rollover without any signs of a catastrophic optical mirror damage or rapid power degradation. Spectrally narrow emission of 0.2 nm at −3 dB and a high wavelength stability with a small current tuning coefficient of 0.7 pm/mA were found. Far-field investigations reveal pre-dominant coupling of lowest order in-phase supermode emission without any sections for adjusting the phase of the electrical field vector for adjacent elements.

Rate equation analysis and non-Hermiticity in coupled semiconductor laser arrays

Optically coupled semiconductor laser arrays are described by coupled rate equations. The coupled mode equations and carrier densities are included in the analysis, which inherently incorporate the carrier-induced nonlinearities including gain saturation and amplitude-phase coupling. We solve the steady-state coupled rate equations and consider the cavity frequency detuning and the individual laser pump rates as the experimentally controlled variables. We show that the carrier-induced nonlinearities play a critical role in the mode control, and we identify gain contrast induced by cavity frequency detuning as a unique mechanism for mode control. Photon-mediated energy transfer between cavities is also discussed. Parity-time symmetry and exceptional points in this system are studied. Unbroken parity-time symmetry can be achieved by judiciously combining cavity detuning and unequal pump rates, while broken symmetry lies on the boundary of the optical locking region. Exceptional points are identified at the intersection between broken symmetry and unbroken parity-time symmetry.

Dynamical Slowing and trapping of light in coupled semiconductor laser arrays

We propose and analyze a new scheme for storing and releasing optical pulses comprising an array of weakly coupled semiconductor lasers. By activating and deactivating individual lasers in the array we are able to manipulate optical pulses, trap them for long periods and release them without noticeable distortion. In addition, the proposed scheme can also regenerate and reshape distorted pulses all-optically. Additional applications such as routing, pulse synchronization and true-time-delaying are also presented and discussed.

The effect of nonlinear gain on the stability of evanescently coupled semiconductor laser arrays

We show that nonlinear gain saturation can enhance the stability of evanescently coupled semiconductor laser arrays.

Frequency control using a complex effective reflectivity in laterally coupled semiconductor laser arrays

Frequency selectivity of a novel type of multielement, multisection laterally coupled semiconductor laser array is studied using the round-trip method. It is found that such a structure should lead to a strong frequency selectivity owing to a periodic dependency of the threshold gain on the frequency. A gain-guided two-coupledcavity device was fabricated. The experimental results show excellent agreement with the theoretical prediction.

Stability of phase locking in coupled semiconductor laser arrays

It is shown that amplitude phase coupling (as described by the linewidth enhancement factor α) leads to unstable phase locking in semiconductor laser arrays with evanescent coupling.

Spatial hole burning problems in evanescently coupled semiconductor laser arrays

The effect of spatial hole burning on laser arrays is theoretically analyzed. Due to the nonuniformity of the lowest order supermode, carriers are unevenly depleted when this mode is excited. This spatial hole burning in carrier concentration reduces any designed discrimination against higher order supermodes. More and more modes are excited as the power level goes up, resulting in broadened radiation patterns. Even when the lowest order mode oscillation can be guaranteed, spatial hole burning modifies the refractive index profile. The intensity distribution of this mode narrows as power increases. The results are broadened radiation patterns and low quantum efficiency. Two methods to overcome these problems are briefly discussed.

Frequency selectivity in laterally coupled semiconductor laser arrays

A longitudinal-mode analysis of a system of laterally coupled waveguided resonators is presented in the coupled-mode approximation. It is shown that variations in the mirror reflectivity of the individual channels result in coupling between the supermodes of the structure. This may lead to mode suppression by modulation of the threshold gain of different Fabry-Perot modes.