The gain spectrum of a (GaIn)As/(AlGa)As single-quantum-well laser diode is precisely measured at various currents in order to quantitatively check the predictions of a microscopic model. The theory includes carrier—carrier and carrier—LO-phonon collisions which lead to optical dephasing and screening of the Coulomb interaction. The measurements are based on a transmission technique using the broad spectrum of a 10 fs Ti:sapphire laser to obtain sufficient signal to noise ratio over a wide spectral range. We obtain excellent agreement between theoretical and experimental gain spectra and thus can clearly demonstrate the predictive capability of our microscopic model.

In this letter, the influence of metal films and dielectric waveguides on the radiation characteristics of light emitting diodes (LEDs) is investigated. Cross and hexagonal surface grating structures are used to excite surface plasmons and waveguide modes in these media. A beam divergence as small as 17° is achieved for a hexagonal grating coated with a 40 nm Ag film. The maximum quantum efficiency is found for a hexagonal grating with a 10-nm-thick Au film and a 250-nm-thick dielectric layer. The optical power emitted by this LED into the solid angle from −30° to 30° is 10% higher than that of an LED without metal film and dielectric layer.

The improved thermal stability of InGaAlAs-based lasers compared with InGaAs-based lasers for 1.5 µm operation is investigated using a combination of low temperature and high pressure techniques. The results indicate that the improved performance of InGaAlAs-based devices is due to a reduction in the contribution of the non-radiative Auger recombination current, I Aug , to the total threshold current, I th , in the InGaAlAs devices. This is due to the higher conduction band offset made possible with the InGaAlAs system which results in a lower hole density in the quantum wells at threshold.

A serious problem of high-power GaAs/AlGaAs laser diodes is the strong mirror heating, which is caused by the carrier density and the correlated nonradiative surface recombination at the cleaved mirrors. Therefore the top electrode was segmented in three parts and the influence of a separate controllable potential in the mirror region on the temperature has been studied. The local temperature was measured using spatially resolved Raman scattering. A substantial reduction of the mirror temperature is possible by applying a suitable potential to the mirror contacts. This may lead to an improvement in reliability in the case where the high mirror temperature is responsible for the degradation of the laser.

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