A superluminescent light-emitting diode in which the spectral width of the output increases with increasing optical output power, thereby allowing the generation of high optical output powers with a broad frequency spectrum that is desirable for some applications of the superluminescent diodes. This desirable characteristic is obtained by structuring the diode to produce a non-uniform gain profile across its active layer. Alternative approaches for achieving the non-uniform gain profile include varying the thickness of the active layer, and varying the current density by employing an asymmetrical channel configuration or an asymmetrical electrical contact strip.