Photonic crystals (PhCs) are periodic dielectric structures that have energy bandgaps for photons. This property is attractive for efficiently controlling and manipulating light in PhCs and for realizing nanocavities with high cavity quality (Q) factors and small mode volumes. Diamond is one of the promising materials to realize PhC cavities due to its relatively large refractive index (2.4) and wide transparency window from the ultraviolet to far-infrared. Diamond also can host a variety of defects centers that can be used as quantum emitters. 

Our group has developed novel fabrication methods using angle etching and quasi-isotropic etching for 1D PhC cavities as well as using thin diamond membranes for 2D PhC cavities. The fabricated PhC cavities with high Q factors can be used for various photonic applications including optomechanics, cavity quantum electrodynamics with defects centers in diamond and visible/telecom diamond photonics.

Optical coupling with a single Tin vacancy center [K. Kuruma, B. Pingault, C. Chia, D. Renaud, P. Hoffmann, S. Iwamoto, C. Ronning, and M. Lončar, Appl. Phys. Lett. 118, 230601 (2021)]: We demonstrate optical coupling between a single tin-vacancy (SnV) center in diamond and a free-standing high-Q photonic crystal nanobeam cavity. We also observe 16-fold enhancement of spontaneous emission rate of a single SnV by coupling to the nanocavity.

Telecommunication-wavelength 2D photonic crystal cavities [K. Kuruma, A. H. Piracha, D. Renaud, C. Chia, N. Sinclair, A. Nadarajah, A. Stacey, S. Prawer, and M. Lončar, Appl. Phys. Lett. 119, 171106 (2021).]: We demonstrate two-dimensional photonic crystal cavities operating at telecommunication wavelengths in a single-crystal diamond membrane. We develop a new technique to fabricate diamond photonic crystal cavities using a scalable fabrication method based on ultra-thin and homogeneous diamond membranes.