The effect of inhomogeneous stress and temperature distribution in GaAlAs/GaAs stripe laser diodes at the pulsation properties was investigated. Under operation, the laser diode is heated. A stronger heating is found in the mirror region causing a shift of the absorption edge of GaAs. The absorption rise up to 1000–2000 cm−1. The parameters of the mechanical stress are also changed. The gain changes as a result of the change of the state of deformation and temperature rise. These effects influence the pulsation properties. The larger the heating in the active region, the lower is the onset current for self-sustained pulsations (SSP).