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The influence of carrier relaxation on the emission dynamics of a semiconductor microcavity laser is investigated using femtosecond optical excitation. For moderate excitation intensities, the dynamics of the output laser pulse becomes significantly slower when the photon energy of the pump laser is tuned from the quantum well band-gap energy towards higher energies. Theoretical calculations reproduce this trend only if the interaction-induced dephasing of the polarization driven by the pump pulse, the formation, and relaxation of the nonequilibrium carrier distribution as well as the chirp of the excitation pulse are taken into account. Additionally, band-structure effects such as excitation of light holes influence the thermalization dynamics and lead to discontinuities in the general trend.

We study the emission dynamics of two In0.2Ga0.8As/GaAs microcavity lasers after femtosecond optical excitation at 20 K. The pulse widths and the peak delays of λ and a 2λ cavity are compared. Pulses as short as 3.3 ps (9.5 ps) and peak delays as short as 8.2 ps (16.5 ps) are obtained with the 2λ cavity (λ cavity). The pulse widths and peak delays are well described by a model based on a rate equation analysis for carrier and photon densities; in particular, the better high speed characteristics of the 2λ cavity compared to the λ cavity are well reproduced.

Higher‐order lateral modes produced in wide GaAs‐GaAlAs DH lasers were spectrally analyzed and photographed by the use of spatially resolved spectroscopy. These modes behave differently in mesa‐ and stripe‐geometry lasers. They were studied in detail as a function of pumping current for the mesa structure. The spacing between lateral modes could be approximated by a simple model based on a sandwich‐type symmetrical dielectric waveguide. Stripe‐geometry lasers follow Hermitian‐Gaussian mode patterns which are produced by parabolic refractive‐index profiles. An anomalous development of mode intensities near threshold was observed in the mesa diode. Immediately above threshold, higher orders dominated the near‐field patterns. Explanation for this could be found in the lateral optical gain profile produced by the interaction of the nonlinear characteristics of the p‐n junction and the geometrical series spreading resistance of the substrate.