Strain-tuning of quantum dot optical transitions via laser-induced surface defects

We discuss the fine-tuning of the optical properties of self-assembled quantum dots by the strain perturbation introduced by laser-induced surface defects. We show experimentally that the quantum dot transition red-shifts, independently of the actual position of the defect, and that such frequency shift is about a factor five larger than the corresponding shift of a micropillar cavity mode resonance. We present a simple model that accounts for these experimental findings.Comment: 9 pages, 6 figures. To appear in Phys. Rev.

Quantum dot nonlinearity through cavity-enhanced feedback with a charge memory

In an oxide apertured quantum dot (QD) micropillar cavity-QED system, we found strong QD hysteresis effects and lineshape modifications even at very low intensities corresponding to less than 0.001 intracavity photons. We attribute this to the excitation of charges by the intracavity field; charges that get trapped at the oxide aperture, where they screen the internal electric field and blueshift the QD transition. This in turn strongly modulates light absorption by cavity QED effects, eventually leading to the observed hysteresis and lineshape modifications. The cavity also enables us to observe the QD dynamics in real time, and all experimental data agrees well with a power-law charging model. This effect can serve as a novel tuning mechanism for quantum dots.Comment: 7 pages, 6 figure

Tuning micropillar cavity birefringence by laser induced surface defects

We demonstrate a technique to tune the optical properties of micropillar cavities by creating small defects on the sample surface near the cavity region with an intense focused laser beam. Such defects modify strain in the structure, changing the birefringence in a controllable way. We apply the technique to make the fundamental cavity mode polarization-degenerate and to fine tune the overall mode frequencies, as needed for applications in quantum information science.Comment: RevTex, 7 pages, 4 figures (accepted for publication in Applied Physics Letters

CNOT and Bell-state analysis in the weak-coupling cavity QED regime

We propose an interface between the spin of a photon and the spin of an electron confined in a quantum dot embedded in a microcavity operating in the weak coupling regime. This interface, based on spin selective photon reflection from the cavity, can be used to construct a CNOT gate, a multi-photon entangler and a photonic Bell-state analyzer. Finally, we analyze experimental feasibility, concluding that the schemes can be implemented with current technology.Comment: 4 pages, 2 figure