Harmonically mode-locked Er-doped fiber laser based on a Sb2Te3 topological insulator saturable absorber

In this letter we present for the first time, to the best of our knowledge, a harmonically mode-locked Er-doped fiber laser with antimony telluride (Sb2Te3) topological insulator material used as a saturable absorber (SA). The SA was prepared via mechanical exfoliation of the bulk material. The 80 nm thick Sb2Te3 layers transferred onto fiber ferrule entirely cover the fiber core. The Er-doped fiber mode-locked laser based on such SA generated optical pulses was centered at 1558 nm with 1.9 ps duration and a fundamental repetition rate of 3.75 MHz. Increasing the pump power results in stable harmonic mode-locked operation up to the 81st harmonic at 304 MHz repetition frequency. The laser was capable of generating optical solitons with 2.2 ps duration. The number of generated harmonics could be tuned only by changing the pump power injected into the laser cavity.