Generation of mode-locked thulium/holmium-doped fiber laser assisted by bismuthene/side polished fiber as saturable absorber

Abstract

An all-fiber passively mode-locked laser is demonstrated near the 2.0 µm wavelength region utilizing thulium/holmium-doped fiber as the gain medium and bismuthene/side-polished fiber (SPF) as saturable absorber (SA). The effect of bismuthene concentration on the performance of the generated mode-locked lasers has also been investigated. In this work, bismuthene was obtained by the exfoliation of bismuth under the ultrasonication technique. Two different concentrations of bismuthene (10 and 20 mg ml−1) were prepared to coat the SPF and be further used as SA. Based on the experimental results, the SA with 10 mg ml−1 concentration of bismuthene induced the most stable mode-locked pulses with good performance. The 10 mg ml−1 bismuthene/SPF SA produced pulses at the center wavelength of 1932.69 nm with the 3 dB bandwidth of 2.59 nm and a signal-to-noise ratio value of 63 dB. The generated pulsed laser exhibits pulse energy of 421.3 pJ, peak power of 261.4 W, and average output power of 4.613 mW. Overall, this work reveals the potential of bismuthene/SPF as an SA for generating mode-locked laser pulses, which is useful in photonics applications.