  We propose and demonstrate the digital resonance tuning of high-Q/Vm silicon
photonic crystal nanocavities using a self-limiting atomic layer deposition
technique. Control of resonances in discrete steps of 122 +/- 18 pm per hafnium
oxide atomic layer is achieved through this post-fabrication process, nearly
linear over a full 17 nm tuning range. The cavity Q is maintained in this
perturbative process, and can reach up to its initial values of 49,000 or more.
Our results are highly controllable, applicable to many material systems, and
particularly critical to matching resonances and transitions involving
mesoscopic optical cavities.
