Mode-Locked Characteristic\nof L‑Band All-Fiber\nLaser with Different 2D and Quasi-2D Perovskite Saturable Absorbers

In recent years, the quasi-2D perovskite material ((PEA)<sub>2</sub>(CsPbBr3)<sub><i>n</i>−1</sub>PbBr<sub>4</sub>)\nhas exhibited outstanding optoelectronic performance and environmental\nstability due to its unique structure, presenting a broad range of\npotential applications. However, structural differences arising from\nvarying values of “<i>n</i>” result in distinct\nnonlinear effects in perovskite materials, which have not been thoroughly\ninvestigated to date. We conducted a comparative analysis of the mode-locked\ncharacteristics of 2D and <i>n</i> = 3, 4, 5, and 6 quasi-2D\nperovskite materials within an Erbium-doped fiber laser (EDFL). All\nmaterials exhibited excellent saturable absorption effects. Besides,\nthe superior performance of the <i>n</i> = 5 quasi-2D perovskite\nmaterial, with an SNR of 72.59 dB, performed best in terms of the\naverage power and single pulse energy. The five-layer quasi-2D perovskites\noffer a suitable bandgap, exciton binding energy, and moderate quantum\nconfinement, leading to effective laser operation. Additionally, the\noptimal nonlinear absorption, refractive index, and thermal stability\ncontribute to stable and high-power laser performance, while suppressing\nsurface states and interface effects. Experimental results indicate\nthat quasi-2D perovskite materials hold significant potential for\napplications in the realm of ultrafast optics.