Fabrication and characterization of photonic crystal microcavities in quasi-single crystal diamond films

In this paper, we report the first realization of photonic crystal cavities in quasi-single crystal diamond of high optical quality. As initial material, we use heteroepitaxial diamond films with a thickness of about 10 μm grown by chemical vapor deposition on Si(001) substrates via iridium/yttria-stabilized zirconia buffer layers. In a first step, we fabricate a free standing membrane by removing the silicon substrate. Afterwards, the diamond film is thinned out to a thickness of 300 nm using dry etching techniques, yielding very smooth surface roughness of 5 nm rms. In a second step, the photonic crystal structure is milled into the diamond film by a focused beam of Ga⁺-ions at an energy of 30 keV. We fabricate ID "nanobeam" cavities in a free standing waveguide as well as 2D photonic crystal structures with several missing holes.