Electro-optic effect in strained and lattice matched multiquantum well structures -- Role of excitonic resonances

Abstract

The well known quantum confined Stark effect (QCSE) is currently being exploited to design optoelectronic devices based on electric field controlled absorption of photons. QCSE is also responsible for strong below exciton resonance changes in refractive index with applied field. These changes can be used for high speed couplers and switches in waveguides. This paper focuses on the use of strain to influence the excitonic resonances in InxGa1-xAs/Al0.2Ga0.8As and In0.53+/-xGa0.47[mnplus]xAs/InGaAsP multiple quantum wells. Experimental results are presented showing the effect of compressive and tensile strain on the refractive index changes. Theoretical results including the important HH-LH band mixing effects are presented for the electrooptic effect. In particular, the contribution of the excitonic part is discussed and is found to dominate the electro-optic effect near the bandedge.