Non-equilibrium asynchronous dual repetition rate solitons mode-locking based on nonlinear polarization rotation

Abstract Single cavity asynchronous dual repetition rate solitons represent a key pathway for the generation of dual-comb sources. The existing single-cavity multiplexing methods generally require dedicated multiplexing designs, which increases system complexity and control difficulty. This work reports the first experimental demonstration of stable non-equilibrium asynchronous dual repetition rate soliton output in a nonlinear polarization rotation mode-locked fiber ring cavity using a polarization-dependent isolator (PD-ISO) without additional multiplexing design. The repetition rate difference between the dual repetition rate solitons can be adjusted by changing the pump power. It is a new scheme for generating asynchronous dual repetition rate soliton states in a polarization-dependent mode-locked cavity to achieve single-cavity dual-comb. Two lasers were designed that both enable controllable evolution from conventional single-soliton mode-locking to asynchronous dual repetition rate soliton state. Theoretical simulations reproduce single-soliton and asynchronous dual repetition rate soliton states. The repetition rate of the two lasers is about 40.10 MHz. As the pump power increased from 164.96 mW to 170.91 mW for laser 2 and from 185.5 mW to 199.58 mW for laser 1, the repetition rate difference increased from 121 Hz to 153 Hz and from 191 Hz to 210 Hz, respectively. It provides a method for electronically controlling the repetition rate difference for the dual comb. The conventional single-soliton mode-locking can be obtained in the 1535 nm and 1560 nm bands by adjusting the polarization controller. This research provides a compact and easily tunable single-cavity dual-comb source with potential for future precision dual-comb measurements applications.