Stefan Strauf

University of California, Santa Barbara

"Semiconductor nano structures for photonic information processing"

Quantum information science is one of the most active research areas and has the potential to substantially influence our every day life in the information age. Among the diverse range of approaches, semiconductor based implementations are highly attractive. This talk presents three different approaches utilizing individual impurities, coupled quantum dots, and single quantum dots inside photonic crystal microcavities.

Individual impurities forming "ultimate quantum dots" constitute the bottom of miniaturization since they consist of only one foreign atom inside a host matrix. Methods how to optically address a single nitrogen impurity in ZnSe and their suitability as a single photon sources will be presented.

Towards more functional units, two InAs quantum dots can be brought in close proximity forming a coupled system. A detailed optical study yields insight into the underlying coupling mechanism. It has been found that the interaction is due to dipole-dipole coupling and energy transfer processes similar to those of light harvesting biomolecules.

Photonic crystal membrane microcavities with embedded quantum dots offer the ability to create new, efficient optical sources of specified wavelength through the control of the dielectric environment. We demonstrate that very few (1 to 3) quantum dots as a gain medium are sufficient to realize photonic crystal lasers with ultra-low lasing thresholds. These results have clear technological implication for future design of microlasers and cavity-QED experiments.