Intrinsic instabilities in narrow stripe geometry lasers caused by lateral current spreading

It is pointed out that lateral current spreading in an otherwise perfectly homogeneous narrow stripe geometry laser causes spontaneous oscillations when the device is operating at the appropriate current level. Intrinsic instabilities of this type are also influenced by diffusion and by the transverse variation of the carrier lifetime. This intrinsic mechanism is discussed on the basis of a simple model consisting of an active slab waveguide with time varying parameters and upon application of a stability analysis.