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We report experimental investigations on a two-section 16-GHz repetition rate InAs/GaAs quantum dot passively mode-locked laser. Near the threshold current, pseudo-periodic Q-switching with complex dynamics is exhibited. Mode-locking operation regimes characterized by different repetition rates and timing jitter levels are encountered up to twice the threshold current. Evolution of the RF spectrum and optical spectrum with current is compared. The different mode-locked regimes are shown to be associated with different spectral and temporal shapes, ranging from 1.3 to 6 ps. This point is discussed by introducing the existence of two different supermodes. Repetition rate evolution and timing jitter increase is attributed to the coupling between the dominant and the secondary supermodes.

The selection of a transverse traveling wave by an inhomogeneous pump profile has been experimentally observed in a class B laser structure. The laser structure consisted of a wide-aperture edge-emitting laser diode operating in pulsed mode to avoid thermal guiding effects. The injection current's profile was modified from the usual top-hat configuration to a Lorentzian-like profile by the inclusion of a 10-mum p-type expitaxial spreading layer. Spatial dependance of the far field on the near field was observed. The same behavior is also demonstrated numerically by use of Maxwell-Bloch equations for semiconductor lasers.

We experimentally investigate the temporal evolution of the power of an external cavity semiconductor laser in the low-frequency fluctuation regime with subnanosecond resolution. We show, for the first time to our knowledge, that generally the laser power drops to a value significantly different from the solitary laser power. We demonstrate the analogy between the recovery of the laser intensity and the turn-on transient of a semiconductor laser.

The spatiotemporal dynamics of linearly and trumpet flared high brightness semiconductor lasers are compared and contrasted using a comprehensive model built up from the microscopic physics. While both devices display complex multi longitudinal mode dynamics, the trumpet flared device is less susceptible to transverse filamentation instabilities and, hence, displays superior time-averaged far-field imaging properties.

Picosecond pulse propagation through a field-enhanced waveguide bulk semiconductor saturable absorber is studied numerically. Fast switching from unsaturated absorption to delayed strong saturation and gain, as well as the predicted dependence of saturation energy on electric field, is based on intraband carrier kinetics and electric-field dynamics in the absorber and can lead to improved, controllable pulse shaping.

Sharply peaked near-field sidelobes are formed when the input optical field pattern interacts with the edges of the current stripe in a semiconductor laser amplifier. The strength of this interaction is shown theoretically to depend principally on the first and second derivatives of the transverse current profile, and hence one can suppress the sidelobes by smoothing the sharp edges in the current injection.

A reliable technique for measuring near field phase fronts of phased-array semiconductor lasers is proposed and demonstrated. Laterally sheared interferograms are generated in a ring-type interferometer with zero optical path difference between two beams, eliminating problems due to equal optical path requirements in other systems. Fourier transform methods are used to extract phase difference information from the nonuniformly illuminated interferograms, and phase discontinuities between adjacent stripes of carrierguided laser arrays are observed. Test data agree with theoretical predictions and far field interpretations.

We investigate the dynamical stability of external-cavity semiconductor lasers with deliberate tilt asymmetries. Experimentally observed low-frequency self-pulsations are explained by small-signal analysis based on a new rateequation model that uses a time-dependent effective reflectivity to include multiple-feedback effects. We observe and explain the dependence of the self-pulsation frequency on the strength and degree of asymmetry of the feedback, on the injection current, and on the external-cavity length. These results are important in interpreting instabilities, chaos, and other complex dynamical phenomena in external-cavity semiconductor lasers.