Conventional solitons and bound-state solitons in an erbium-doped fiber laser mode-locked by TiSe-based saturable absorber.

Conventional solitons (CSs) as well as bound-state solitons in a passively mode-locked erbium-doped fiber (EDF) laser based on 1 T-phase titanium diselenide (1 T-TiSe) saturable absorber (SA) have been systematically demonstrated for the first time. The mode locker is assembled by sandwiching the 1 T-TiSe film between two fiber ferrules to improve compatibility with the all-fiber-integrated ring cavity configuration. The modulation depth, saturation intensity and nonsaturable loss of the prepared 1 T-TiSe SA are 14.36%, 1.33 MW cm and 9.44%, respectively. The system is switchable between two states: CS and bound-state CS, by carefully adjusting the orientations of the polarization controller (PC). In the CS mode-locked regime, the oscillating wavelength is centered at 1558.294 nm with a pulse duration of 1.74 ps, a pulse repetition rate of 3.23 MHz and a maximum average output power of 2.904 mW. In the bound-state CS regime, two identical solitons form the bound-state pulses with a temporal separation of 6.1 ps, and the bound-state pulses are equally distributed at a repetition rate of 3.23 MHz, corresponding to the fundamental cavity repetition rate. The experimental results further indicate that 1 T-TiSe SA is competitive with the existing SAs explored so far and will promote the applications of 1 T-TiSe-based SAs in the field of ultrafast lasers.