Dual-comb soliton rains based on polarization multiplexing in a single-walled carbon nanotube mode-locked Er-doped fiber laser

We experimentally demonstrate tunable dual-comb soliton rains in a polarization multiplexing fiber laser based on a single-walled carbon nanotube. The repetition frequency difference of dual-comb pulses is about 39 Hz, with a maximum extinction ratio of 29 dB. With suitable polarization states, one of the dual-comb pulses switches into soliton rain sequence with chirped isolating soliton trains. The signal-to-noise ratio reaches 61 dB, which is 11 dB higher than that of the normal dual-comb pulses. The intervals between chirped isolating solitons are distributed progressively, and the number of isolating solitons can be flexibly tuned from 2 to 11 by adjusting polarization state or pump power. Our work will provide support for further understanding of interaction dynamics of solitons and give a new route to the application of precision measurement.