Optophononic Polarization Rotation in Coupled Quantum Dots

We theoretically study the use of coherent behavior of phonons in coupled quantum dots. A coherent Fano-type quantum interference between a single-dot polaron state and a spatially indirect exciton gives rise to a spectrally asymmetric optical response of the coupled dot system and a phonon-induced optical transparency [1]. Optical selection rules dictate which exciton spin state participates in this Fano-type interference. Consequently, the optical response of the optically driven system to a weak probe is polarization dependent, with a Fano- or a Lorentzian-shape spectral profile for orthogonal polarizations. These two spectral configurations have different refractive indices, and result in a situation similar to the magneto-optic Kerr or Faraday effects. We theoretically demonstrate an optophononic polarization due to the Fano-type interference induced by the coherent phonon behavior. We extend the scope of the treatment to a wide range of Fano asymmetries. We calculate the asymmetric spectrum using a fully quantum mechanical, master equation formalism that accounts for both weak- and strong-coupling regimes of the exciton with the lattice vibrations of the dots.

[1] M. L. Kerfoot et al., Nature Commun. 5, 3299 (2014).