Indices of refraction of InGaAs/Alas/AlAsSb multiple-quantum-wells measured by an optical waveguide technique

InxGa1-xAs/AlAs/AlAsySb1-y coupled-double-quantum-wells (CDQWs) were grown on InP substrates by molecular beam epitaxy (MBE). The structural quality was examined by X-ray diffraction (XRD) measurements using a high-resolution four-crystal diffractometer. The indices of refraction n and thickness for a series of CDQWs were measured using a prism coupler method at two discrete wavelengths. The thickness of CDQWs corresponds well with that obtained from XRD measurements. We found that the effective values of n of these CDQWs were slightly smaller than those obtained by linearly averaging n of the constituent layers of the CDQWs. This indicates that the quantum confinement of the carriers give rise to the shift of the effective index of refraction of CDQWs.