Electrorefraction in InGaAs/InP Multiple Quantum Well Heterostructures.

We report the first absolute measurement of electric-field- induced changes in refractive index in InGaAs quantum well heterostructures. Even for wavelengths as far as 40 meV below the absorption edge, excitonic effects dominate electro-optic phase modulation. This effect close to resonance yields index changes two orders of magnitude larger than in bulk material. We find that the size of the index change, its dependence on applied voltage, and its behaviour with wavelength are well- described in terms of the quantum confined Stark effect on excitonic absorption.