Color centers in diamond: bright single photon emission & optical interfaces
Prof. Dr. Christoph Becher (Universität des Saarlandes)

In recent years color centers in diamond have attracted significant interest for applications in quantum information. Examples are the NV center which is well suited as quantum memory due to its long spin coherence times and “new” color centers, e.g. based on Cr or Si, which are high-brightness single photon emitters. I will discuss fabrication and spectroscopic investigation of such color centers, in particular Silicon-vacancy centers, for which we recently have demonstrated record high single photon emission rates and very narrow emission lines at room temperature.

For many of the applications in quantum information, e.g. quantum networks, it is essential to couple single color centers to a cavity mode with high quality-factor Q and small modal volume in order to coherently manipulate, readout and transfer the center's quantum state. We follow two different routes towards realization of such optical interfaces: coupling to microcavities based on fiber mirrors or microcavities defined within diamond-based photonic crystals (PhC). We demonstrate fiber-based cavities with lengths of a few microns and finesse of few hundred, sufficient for observing modified spontaneous emission. For the second approach, we present optimized designs based on Fourier- and real space analysis of PhC defect cavity structures. We fabricate PhC microcavities in quasi-single crystal diamond by focused ion beam milling and dry etching techniques. First structures show pronounced cavity modes near the emission wavelength of Silicon-vacancy centers.