Broad Area Semiconductor Amplifiers and Lasers display instability of the homogeneous state typically related with self-focusing nonlinearities, inducing multi-transverse mode operation and filamentation that deteriorates the beam quality. We show that the emission of these amplifiers and lasers can be efficiently stabilized by introducing simultaneous modulations of pump and refractive index in transverse and longitudinal directions. The pattern forming instabilities are efficiently suppressed even for the case of large linewidth enhancement factors by the intertwinement between both inphase modulations leading to stable beams.