Modern solid-state quantum optics are carried out using novel photonic crystals with the unique ability to control light propagation. Among possible applications are light guides and switches for optical communications. By including single-quantum active elements in the form of quantum dots (see Fig 1) into the crystal structure one may use the light-controlling ability of the photonic crystal to realize unique light-matter coupling phenomena. This may have applications in quantum communications as single-photon sources and/or other quantum-active elements of the communication line. 

Fig 1: Sketch of self-assembled quantum dot designed to confine carrier motion in all directions, leading to quantization of the allowed energy levels as known from atomic physics. Different colours indicate different kinds of atoms.

Central to the understanding of the dynamics in such systems is suitable models of both the quantum dot and the photonic crystal. The models should be sufficiently advanced that they capture the essential dynamics, yet simple enough that they can be applied to a range of systems as large as possible.

Special and widely used kind of photonic crystals, the so-called planar photonic crystals, are made by etching a periodic array of holes into a thin semiconductor membrane as illustrated in Fig. 2. These kinds of crystals are promising because of their relatively easy fabrication, but are hard to understand theoretically.

In this project we set up a model of a general planar photonic crystal using the Green’s tensor for the electromagnetic field both in and outside the crystal. With such a model we will be able to predict in principle all light propagation inside and outside the photonic crystal.

The radiation pattern outside the photonic crystal from quantum dots inside the crystal is of special interest, as is light-matter coupling in wave guides in the photonic crystal for use as single-photon sources or slow light devices. A special configuration which we hope to investigate is a system of dipole coupled quantum dots in the crystal. This represents a simple realization of a realistic coupled quantum system and may have applications in quantum information technologies.

Fig 2: Sketch of PC slab, consisting of a thin semiconductor membrane with a periodic array of air holes. Active elements in the form of quantum dots (indicated in red) may be embedded within the structure.

Links and related material:

Philip Trøst Kristensen, Peter Lodahl and Jesper Mørk;
“Light propagation in finite-sized photonic crystals: Multiple scattering using an electric field integral equation”, arXiv:0908.4240v1 [math-ph].

Philip Kristensen, A. Femius Koenderink, Peter Lodahl, Bjarne Tromborg, and Jesper Mørk
"Fractional decay of quantum dots in real photonic crystals." Optics Letters, Vol. 33, Issue 14, pp. 1557-1559 (2008)

Contact

For more information please contact Philip Trøst Kristensen