Passively mode-locked Er-doped fiber laser based on a semi-metallic InBi saturable absorber

Two-dimensional (2D) materials have drawn great interest for their applications in mode-locking due to their unique optical nonlinearities. However, most of these 2D materials are semi-conductors. In this study, a new kind of semi-metal indium bismuth (InBi) is reported which is a topological nodal-line semi-metal with exotic physical properties. The InBi nanomaterials were prepared through a liquid phase exfoliation method with an average thickness of 32.8 nm. The saturable absorption property was measured and passive mode-locking operation was successfully achieved in the Er-doped fiber laser. It exhibited a modulation depth of 3.21%, a saturable intensity of 100 MW cm(-2) and a pulse width about 859.97 fs corresponding to the central wavelength of 1562.27 nm and 3 dB bandwidth of 2.98 nm. The experimental results open a new avenue for the use of semi-metals InBi nanomaterials in lasers and photonics applications.