Harmonic Mode-Locking in Bidirectional Domain-Wall Soliton Fiber Lasers

Polarization domains and self-mode-locked pulses in an erbium-doped fiber laser

“…The typical feature of such pulses is that the polarization of light is periodically switched between two orthogonal directions at round-trip frequency. And for practical applications, PDs were studied to achieve the square-shaped pulse [15][16][17][18][19] and have been used in optical fibers as topological bits for data transmission [23] . Due to the existence of birefringence in fiber, the fundamental mode contains two orthogonal polarization modes with different propagation constants.…”

“…Due to the existence of birefringence in fiber, the fundamental mode contains two orthogonal polarization modes with different propagation constants. PDW pulses are obtained due to the cross coupling of the two orthogonal polarization modes [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . In 2009, Zhang et al [6] first experimentally observed PDW solitons in weakly birefringent cavity fiber lasers, which were formed due to the strong coherent cross-polarization coupling of light in the fiber lasers.…”

“…The pulse durations of the PDs can be changed with the variation of the cavity parameters, and the PDWs are usually formed as bright pulses, dark pulses, or bright-dark pulse pairs with different temporal profiles [12][13][14][15][16][17][18][19] . Under a certain cavity condition, the PDs will split to form irregularly distributed multidomains [15][16][17] , harmonic PDWs [18] , or evolve into other types of pulses [20,22] . The research shows that the strength of the coherent or incoherent cross coupling can induce various domain states.…”