Deterministic and electrically tunable bright single-photon source
A. K. Nowak , S. L. Portalupi, V. Giesz , O. Gazzano , C. Dal Savio , P.-F. Braun , K. Karrai , C. Arnold , L. Lanco , I. Sagnes, A. Lemaître & P. Senellart.
http://www.nature.com/articles/ncomms4240
The scalability of a quantum network based on semiconductor quantum dots lies in the possibility of having an electrical control of the quantum dot state as well as controlling its spontaneous emission. The technological challenge is then to define electrical contacts on photonic microstructures optimally coupled to a single quantum emitter. We have developed a novel photonic structure and a technology allowing the deterministic implementation of electrical control for a quantum dot in a microcavity.
We study a λ/2- AlAs cavity surrounded by GaAs/AlGaAs Bragg mirrors, doped in the p-i-n diode configuration. To apply an electric field to the structure, rather than using simple pillar cavities, we use pillars connected to a larger ohmic-contact surface with four 1D-bridges (1μm width). The fundamental mode of the structure is confined in the center of the pillar with a low penetration into the bridges. Quality factors of the connected pillars are similar to the ones obtained for isolated pillars. Deterministic positioning of a single QD at the centre of the connected pillar structure is performed using an advanced single in-situ optical lithography step. Upon the application of a voltage, the QD line is electrically tuned into resonance with the cavity mode. An experimental extraction efficiency as large as 55% is demonstrated.
