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The coherence of broad-area laser diodes with quantum dot gain medium is improved by frequency-selective feedback. A linewidth of 5–10 GHz at power levels of 10–140 mW is achieved in the wavelength region around 1240 nm, where no other good semiconductor lasers are available. The tuning range is at least 20 nm. [ABSTRACT FROM AUTHOR]

The length-scale selection in complex emission patterns spontaneously arising in broad-area vertical-cavity surface-emitting lasers is studied experimentally. The wavenumbers of individual tilted wave modes show a square-root-like dependence on the detuning between emission frequency and longitudinal cavity resonance, in accordance with theoretical expectations. The absolute values of the wavenumbers are in good qualitative agreement with calculations taking into account the reflection properties of the Bragg reflectors and dispersion. [ABSTRACT FROM AUTHOR]

We investigate the response of a system far from equilibrium close to an oscillatory instability to the induction of phase singularities. We base our investigation on a numerical treatment of the complex Ginzburg–Landau equation (CGLE) in two spatial dimensions, which is considered as an order-parameter equation for lasers and other nonlinear optical systems. Defects are randomly generated by a spatially modulated linear growth rate. In the amplitude-turbulent regime, no qualitative change of behaviour can be detected. Phase-turbulent patterns emerging due to the Benjamin–Feir instability are destroyed by the externally injected defects. One observes either states consisting of spiral structures of various sizes which resemble the vortex glass states of the unperturbed system or a travelling wave pattern containing moving topological defects. In parameter space, both states are separated by a well-defined phase boundary which is close to the line separating convectively from absolutely stable travelling waves. [ABSTRACT FROM AUTHOR]

We analyze the potential for the spin manipulation of vertical-cavity surface-emitting lasers (VCSELs) by operating them electrically and injecting additional spin-polarized carriers by polarized optical excitation. The output polarization of the VCSELs can be easily controlled by the spin orientation of the optically injected carriers when the injection current does not exceed the threshold current. [ABSTRACT FROM AUTHOR]