Dynamics of semiconductor laser arrays.

This thesis presents a theoretical and experimental study of semiconductor laser arrays. A time-dependent coupled-mode model is developed for analyzing the well-confined evanescently coupled index-guided arrays. The stability conditions for twin-stripe devices is derived and interpreted physically. With this model, both twin-stripe and multi-stripe devices are simulated. From these simulations, the stable outputs with lateral in-phase and out-of-phase modes are observed. Through changing the coupling coefficient, periodic and irregular outputs could also be found. These simulation results agree the stability conditions. In order to analyze most weak-guiding structures, a continuum model developed from the the beam propagation method based on the fast Fourier transform is employed. Both gain-guided and index-guided twin-stripe arrays are simulated utilizing this model. In the case of the index-guided arrays, both unstable and stable (out-of-phase) outputs are observed. The temporal energy exchange between the two stripes were noted. For the gain-guided case, stable, synchronuous Q-switched spikings, as well as irregular spiking, are observed by varying the spacing between the two laser stripes. The spatio-temporal behavior of the outputs of twin-stripe and 8-stripe devices are measured with a streak camera under continuous wave and pulsed operations. The synchronuous spiking oscillations from each stripe are noted in both arrays. By using a spectrometer, we found that the twin-stripe gain-guided device with low pump current, was single-lateral mode and single mode, while the 8-stripe CSP array displays multiple modes laterally and longitudinally. The modulation behavior of various laser arrays are measured by using a spectrum analyzer. It is found that the laser arrays are still modulable even if their outputs can still be unstable under cw operation.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105623/1/9135716.pdfDescription of 9135716.pdf : Restricted to UM users only