Lineshape of a vertical cavity surface emitting laser

We report on the experimental study of the lineshape of an air-post GaAs/AlGaAs Vertical-Cavity Surface-Emitting Laser (VCSEL). The signal is obtained by heterodyne with a narrow linewidth extended-cavity laser. This technique allows to fully take into account the entire spectrum of frequency fluctuations. In this way we can distinguish a Lorentzian and a Gaussian contributions to the lineshape, obtaining a clear picture of the dependence of the emission spectrum on the pump current, The study also includes the effects on the laser lineshape of the secondary transverse modes fluctuations. (C) 2002 Elsevier Science B.V. All rights reserved.