Femtosecond pulse generation from a topological insulator mode-locked fiber laser

TLDR

A PVA‑based Bi₂Se₃ saturable absorber with 12 MW cm⁻² saturation intensity and ~3.9 % modulation depth was integrated into an anomalous‑dispersion fiber ring laser, enabling mode‑locking at a 25 mW pump threshold. The laser produced ~660 fs pulses centered at 1557.5 nm, confirming that the thin PVA‑based TI saturable absorber is an effective ultrafast device.

Abstract

We reported on the generation of femtosecond pulse in an anomalous-dispersion fiber ring laser by using a polyvinyl alcohol (PVA)-based Topological Insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device.