A technique, based on quantum well (QW) intermixing, has been developed for the post growth, spatially selective tuning of the QW bandgap in a semiconductor laser structure. High energy (MeV) ion implementation is used to create a large number of vacancies and interstitials in the device. During high temperature processing (rapid thermal annealing), these defects simultaneously enhance the intermixing of the QW and the barrier materials, producing a blue shift of the quantum well bandgap, and are annealed out. Increases in the bandgap energy of greater than 100 nm at 1.55 (mu) m in InGaAs/InGaAsP/InP structures can be achieved, while absorption losses are unaffected or reduced. Absorption spectroscopy in the waveguide geometry is used to quantify any excess loss in the structure. Using a simple masking scheme to spatially modify the defect concentration, different regions of a wafer can be blue shifted by different amounts. This allows the integration of many different devices such as lasers, detectors, modulators, amplifiers and waveguides on a single wafer using only a single, post-growth processing step. The performance of both passive (waveguide) and active (laser and amplifier) devices produced using this technique will be described, as well as the practicality of this technique in the production of photonic integrated circuits.