  Integrating solid-state quantum emitters with nanophotonic resonators is
essential for efficient spin-photon interfacing and optical networking
applications. While diamond color centers have proven to be excellent
candidates for emerging quantum technologies, their integration with optical
resonators remains challenging. Conventional approaches based on etching
resonators into diamond often negatively impact color center performance and
offer low device yield. Here, we developed an integrated photonics platform
based on templated atomic layer deposition of TiO2 on diamond membranes. Our
fabrication method yields high-performance nanophotonic devices while avoiding
etching wavelength-scale features into diamond. Moreover, this technique
generates highly reproducible optical resonances and can be iterated on
individual diamond samples, a unique processing advantage. Our approach is
suitable for a broad range of both wavelengths and substrates and can enable
high-cooperativity interfacing between cavity photons and coherent defects in
diamond or silicon carbide, rare earth ions, or other material systems.
