High-contrast Kerr Frequency Combs
  Kerr frequency combs with depressed harmonic at the optical pump frequency are theoretically explained and experimentally demonstrated. This result is achieved in a MgF$_2$ photonic belt resonator having reduced density of modes in its spectrum and configured with the add-drop optical couplers. \copyright 2016 California Institute of Technology. Government sponsorship 
Ivan S. Grudinin, Vincent Huet, Nan Yu, Michael L. Gorodetsky, Andrey   B. Matsko, Lute Maleki
physics.optics