The implementation of multiple band gaps on a single InP substrate with an InGaAs/InGaAsP quantum well laser structure via the control of local defect concentrations in the process of inductively coupled argon (Ar) plasma enhanced quantum well intermixing is reported. With multistep plasma exposure, different levels of near-surface point defect concentrations are established in different areas, which lead to different extents of band gap modification in a single-step rapid thermal annealing (RTA). Three distinct band gaps with blueshifts of 84, 66, and 3 nm with respect to that of the as-grown sample are achieved in a process involving two steps of Ar plasma exposure and a single step of annealing in nitrogen ambient at 600 degrees C for 2 min. As an indication of material quality preservation, no intensity reduction and linewidth broadening in the photoluminescence caused by the process has been observed. This work demonstrates a practical approach of multiple band gap modification for the InP-based photonic integrated circuit application. (c) 2005 American Vacuum Society.