Telecommunication-wavelength two-dimensional photonic crystal cavities in a thin single-crystal diamond membrane

We demonstrate two-dimensional photonic crystal cavities operating at telecommunication wavelengths in a single-crystal diamond membrane. use high-optical-quality and thin (~ 300 nm) membrane, supported by polycrystalline frame, to realize fully suspended with high theoretical quality factor of ~ $8\times10^6$ relatively small mode volume ~2$({\lambda}/n)^3$. The are fabricated the membrane using electron-beam lithography vertical dry etching. observe cavity resonances over wide wavelength range spanning O- S-bands (1360 nm-1470 Q factors up ~1800. Our method offers new direction for on-chip nanophotonic applications telecommunication-wavelength range.