Disclosed is a semiconductor laser. The semiconductor laser includes a semiconductor chip that includes an active layer and emits radiation in a main radiating direction. The active layer is structured in a direction perpendicular to the main radiating direction to reduce heating of the semiconductor chip by spontaneously emitted radiation, and the active layer has the form of a mesa that comprises side walls that form a resonator in such a way as to reduce the spontaneous emission in the active layer in a direction perpendicular to the main radiating direction.