In this paper we shall discuss techniques for accurate, non-destructive, optical characterisation of structures fabricated using quantum well intermixing (QWI). Spatially resolved photoluminescence and Raman spectroscopy were used to characterise the lateral bandgap profiles produced by impurity free vacancy disordering (IFVD) technology. Different features were used to examine the spatial resolution of the intermixing process. Features include 1:1 gratings as well as isolated stripes. From the measurements, the spatial selectivity of IFVD could be identified, and was found to be ∼4.5 μm, in contrast with the spatial resolution of the process of sputtering induced intermixing, which was found to be ∼2.5 μm. In addition, PL measurements on 1:1 gratings fabricated using IFVD show almost complete suppression of intermixing dielectric cap gratings with periods less than 10 microns. Finally, some insight into the limitations and merits of PL and Raman for the precision characterisation of QWI will be presented.