Dispersion engineered high-Q silicon Nitride Ring-Resonators via Atomic   Layer Deposition
  We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition (ALD). Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. All results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum. 
Johann Riemensberger, Klaus Hartinger, Tobias Herr, Victor Brasch,   Ronald Holzwarth, Tobias J. Kippenberg
physics.optics