All-polarization-maintaining multipulse thulium-doped fiber laser based on nonlinear polarization rotation

Soliton molecule multi-pulse output was achieved based on an all-polarization-maintaining thulium-doped fiber, with a central wavelength of 1970.6 nm, a pulse repetition frequency of 12.39 MHz, and an average output power of 8 mW. Due to the low pulse output power obtained, it was impossible to measure the pulse width using a commercial autocorrelator, and the oscilloscope could not resolve pulse intervals below 50 ps, thus the symmetric waveform of the soliton molecule was not observed. As the pump power varied, the laser could switch between soliton cluster pulse and noise-like pulse outputs. The laser structure consisted of an all-polarization-maintaining ring cavity pumped by a 793 nm laser.