Electrorefraction in quantum dots: dependence on lateral size and shape

Abstract

Photonic switches require low loss polarization independent phase shifting elements. In a composite quantum well, a 0.46 mm phase shifter provides a /spl pi//4 phase shift by combining the Quantum Confined Stark Effect (QCSE) and carrier depletion effect. We investigate whether the discrete energy levels and the high peak absorption in quantum dots (QDs) provide an opportunity for increasing the electro-refraction. The electro-refraction in strained cylindrical InAs/GaAs QDs is explored using a numerical model based on the 4/spl times/4 Luttinger-Kohn Hamiltonian. The excitonic states are calculated by matrix diagonalization with plane-wave basis states. We observe that the QCSE sharply increases with the height of the QD and is also optimized for small radius QDs. The QCSE in pyramidal QDs is considerably larger than in squares or cylinders. We finally present large electro-refraction in, cone shaped pyramidal QDs.