Thulium Doped Mode-Locked Fiber Lasers Utilizing Hollow Core Anti-Resonant Fiber Filled With Mxene Ti3c2Tx as Saturable Absorber

We present a simple and compact saturable absorber (SA) fabricated by filling a hollow-core anti-resonant fiber (HC-ARF) with MXene Ti₃C₂T_x. The proposed SA exhibits exceptional nonlinear saturable absorption property with a modulation depth of 30% at 2 μm and a remarkably low insertion loss of 3.5 dB, which is realized by manipulating the MXene Ti₃C₂T_x thickness coated to the outer tubes of the HC-ARF. Conventional soliton mode locking can be achieved by incorporating the SA into a thulium-doped fiber laser. The pulse width is 1.72 ps and the pulse signal to noise ratio is larger than 70 dB. To the best of our knowledge, it is confirmed for the first time that the filling HC-ARF with MXene Ti₃C₂T_x as SA can achieve mode-locking ultrashort pulses operating in the 2 μm band. We believe this work can open a new avenue for exploring the integration of HC-ARF filled with various two-dimensional materials as SA devices.