The maturity of GaAs/AlAs-based technology enabled the fabrication of highly efficient diode lasers based on (AlGaIn)As/GaAs as well as (AlGa)As/GaAs active regions. Furthermore, these material systems have proven to be widely adaptable, because the GaAs/AlAs system allows for the fabrication of various cavity concepts including in-plane as well as vertically emitting laser structures and the emission wavelengths of the above-mentioned active regions can be tailored from the red to the near-infrared wavelength regime. However, the fabrication of GaAs-based telecommunication lasers proved to be difficult due to the high quality requirements in combination with strain-induced defect formation. While the demonstration of 1.3 μm lasers based on Ga(AsSb)/GaAs [1] as well as (GaIn)(NAs)/GaAs [2] was possible, (GaIn)(AsP)/InP and (AlGaIn)As/InP remained the dominant material systems for lasers emitting at wavelengths longer than 1.2 μm.

Systematic photoluminescence measurements on a series of GaBixAs1−x samples are analyzed theoretically using a fully microscopic approach. Based on sp3s⁎ tight-binding calculations, an effective k·p model is set up and used to compute the band structure and dipole matrix elements for the experimentally investigated samples. With this input, the photoluminescence spectra are calculated using a systematic microscopic approach based on the semiconductor luminescence equations. The detailed theory-experiment comparison allows us to quantitatively characterize the experimental structures and to extract important sample parameters.

Ultrafast femtosecond timescale dynamics in Vertical External Cavity Surface Emitting Lasers (VECSELs) have recently been employed to achieve record average power and duration mode-locked pulses by employing different types of saturable absorbers and Kerr Lens elements. Microscopic many-body dynamics are expected to dominate when attempting to push pulse durations below 100 fs. We present a preliminary microscopic simulation of ultrafast mode-locking in order to expose the role of hot carrier distributions in establishing ultrafast mode-locking.

The microscopic theory for the nonequilibrium optical properties of VECSELs is summarized. Detailed experiments of VECSELs under two-color operation conditons are performed utilizing streak camera measurements of the laser output. A statistical analysis reveals the stability range of two-color emission and shows that this operation mode is possible even in the presence of relatively large losses.