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 thep‐njunction and the geometrical series spreading resistance of the substrate.