Electro-refraction in quantum dots: dependence on lateral size and shape

• Published in: IEEE transactions on nanotechnology Vol. 3; no. 2; pp. 270 - 274
• Main Authors: Prasanth, R., Haverkort, J.E.M., Wolter, J.H.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2004; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Absorption; Carrier confinement; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electrooptical effects; Energy levels; Energy states; Exact sciences and technology; Mathematical models; Noise levels; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Phase shifters; Physics; Polarization; Potential well; Quantum dots; Quantum wells; Shape; Stark effect; Switches; Matrix diagonalization; Photorefractive effect; Excitons; Optical switches; Quantum dots; Electro-optical effects; Digital simulation; Quantum confined Stark effect
• ISSN: 1536-125X; 1941-0085
• DOI: 10.1109/TNANO.2004.828533

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 the 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 a box or cylinders. We find a peak electro-refraction of /spl Delta/n=0.35 in cone-shaped pyramidal QDs, which is a factor of 35 larger than in the quantum-well case. Finally, in the waveguide geometry, we find an electro-refraction of 1.3/spl times/10/sup -2/ at a residual QD absorption of 0.15 dB/cm.