Si-based passively mode-locked 20 GHz QD-MLL. (A) and (B) Schematic diagrams of the epitaxial structure and the 20 GHz MLL device of quantum dot mode-locked laser on silicon, respectively. (C) Optical spectrum and corresponding optical linewidth of each mode within 10 dB. (D) RF spectrum in a 50 GHz span view. (E) The single-sideband phase noise plot under the narrowest pulse width condition.