title: Polarization domain wall pulses in a microfiber-based topological insulator fiber laser.
abstract: Topological insulators (TIs), are novel two-dimension materials, which can act as effective saturable absorbers (SAs) in a fiber laser. Moreover, based on the evanescent wave interaction, deposition of the TI on microfiber would create an effective SA, which has combined advantages from the strong nonlinear optical response in TI material together with the sufficiently-long-range interaction length in fiber taper. By using this type of TI SA, various scalar solitons have been obtained in fiber lasers. However, a single mode fiber always exhibits birefringence, and hence can support two orthogonal degenerate modes. Here we investigate experimentally the vector characters of a TI SA fiber laser. Using the saturated absorption and the high nonlinearity of the TI SA, a rich variety of dynamic states, including polarization-locked dark pulses and their harmonic mode locked counterparts, polarization-locked noise-like pulses and their harmonic mode locked counterparts, incoherently coupled polarization domain wall pulses, including bright square pulses, bright-dark pulse pairs, dark pulses and bright square pulse-dark pulse pairs are all observed with different pump powers and polarization states.
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Jingmin
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Xingliang
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Shumin
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen, 518060, China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Shenzhen key laboratory of laser engineering, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China.
authors.forename: Peiguang
authors.initials: P
authors.lastname: Yan
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Mengmeng
authors.initials: M
authors.lastname: Han
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Zhaoguang
authors.initials: Z
authors.lastname: Pang
authors.affiliation: College of Physics Science and Information Engineering, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China.
authors.forename: Zhenjun
authors.initials: Z
authors.lastname: Yang