Mode-Locking and Q-Switching in Holmium Doped Fiber Laser Using Topological Insulator (Sb₂Te₃) as Saturable Absorber

This work demonstrates mode-locking and Q-switching in a holmium-doped fiber laser (HDFL) using topological insulator (TI) antimony telluride (Sb2Te3) as the saturable absorber (SA). The TI was drop-casted on an arc-shaped fiber to generate mode-locked pulses and used in thin-film form to generate Q-switched pulses. The mode-locked pulses obtained were centered at 2081.1 nm with a repetition rate of 13.4 MHz, signal-to-noise ratio of 42 dB, and 1.85 ps pulse width. The Q-switched pulses were generated at the center wavelength of 2086.3 nm within the pump power of 1.55 W until 1.80 W. Within this range, the repetition rate peaked at 50.76 kHz and the pulse width dropped to a minimum value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.64~\mu $ </tex-math></inline-formula>s. To the best of the author’s knowledge, this is the first work to use a topological insulator in an HDFL to generate both mode-locked and Q-switched pulses.