Design of Photonic Crystal Microcavities in Diamond for Quantum Information

We here consider photonic crystal (PhC) microcavities in diamond films for QI applications. The PhC structures consist of a thin free-standing diamond membrane (slab) with a periodic array of circular air holes. Cavities are formed by point or line defects in the triangular lattice of air holes. Analogous PhC slab structures have been successfully employed in semiconductor quantum optics yielding strong coupling of single semiconductor quantum dots. For diamond, however, the crucial parameter is the relatively low refractive index of n = 2.4, leading to smaller PhC bandgaps and weaker mode localization. It is thus important to investigate whether one can still realize small mode volume high-Q cavities. Even taking into account experimental imperfections as fabrication tolerances, material absorption and imperfect spatial placement of the emitters, such high Q factors should be sufficient for demonstrations of emitter-cavity coupling and QI applications.