Si${}_3$N${}_4$ optomechanical crystals in the resolved-sideband regime

We demonstrate sideband-resolved Si${}_3$N${}_4$ optomechanical crystals supporting ${10}^5$ quality factor optical modes at 980 nm, coupled to $\approx 4$ GHz frequency mechanical modes with quality factors of $\approx 3000$. Optomechanical electromagnetically induced transparency and absorption are observed at room temperature and in atmosphere with intracavity photon numbers of the order of ${10}^4$.