Proton irradiation followed by rapid thermal annealing was used to selectively induce layer intermixing and thus shift the emission wavelengths of GaAs–AlGaAs graded-index separate-confinement-heterostructure quantum well lasers. Up to 40 nm shifts were observed in 4 &mgr;m ridge waveguide devices irradiated to a dose of1.5×1016 cm−2.Although the wavelength shifts were accompanied by some degradation in the lasing threshold current and differential quantum efficiency, they were still quite acceptable at moderate wavelength shifts. This technique provides a simple and promising postgrowth process of integrating lasers of different wavelengths for wavelength-division-multiplexing applications. ©1997 American Institute of Physics.