The quantum well intermixing has been developed for tuning the bandgap of III-V compound semiconductor materials using Argon plasma at the postgrowth level. The inductively coupled plasma shows an advantage of a larger blue-shift with a narrower linewidth than the plasma generated using reactive ion etching system. A wide range of III-V compound material systems covering the wavelength range from 700 to 1600nm has been intermixed using the technique. Using the multiwidth quantum-well probe structure, the intermixing mechanism was investigated. The point defects are created at near sample surface during plasma exposure and upon annealing they propagate downwards to promote quantum-well intermixing. Such technique gives a spatial resolution of better than 2.5 mu m utilizing the stress inducing SixNy mask. The extended cavity laser has been demonstrated using selective plasma induced intermixing with a low loss intermixed waveguide of similar to 2.3cm(-1). The result indicates a promising approach of lateral bandgap tuning for high-density photonic integrated circuits at postgrowth level using a plasma system widely used in the semiconductor industry. (c) 2005 Published by Elsevier B.V.