We demonstrate the fabrication of photonic crystal nanobeam cavities with
rectangular cross section into bulk diamond. In simulation, these cavities have
an unloaded quality factor (Q) of over 1 million. Measured cavity resonances
show fundamental modes with spectrometer-limited quality factors larger than
14,000 within 1nm of the NV center's zero phonon line at 637nm. We find high
cavity yield across the full diamond chip with deterministic resonance trends
across the fabricated parameter sweeps
