GeS₂ Nanosheets as Saturable Absorbers for High Signal-to-Noise Ratio in an L-Band Ultrafast Pulsed Laser

Recently, two-dimensional (2D) materials have attracted increasing attention as promising saturable absorbers (SAs) due to their excellent optoelectronic properties, which enable ultrashort duration, low time jitter, and good stability. Here, we have successfully proposed and demonstrated an L-band (@1568 nm) mode-locked fiber laser assisted by GeS2–SA. A high signal-to-noise ratio (SNR) ultrafast pulse generation with weak correlation van der Waals GeS2 nanosheets has been prepared for the development of ultrashort pulse output. The modulation depth and saturation intensity of GeS2–SA are 6.1% and 0.012 MW/cm2, respectively. Nanoscale GeS2–SA-based erbium-doped fiber pulse laser is demonstrated with a high SNR of 71 dB and a pulse duration of 907 fs. This result extends the family of 2D material-based L-band pulsed lasers and proves that the GeS2 nanosheets hold promise for application in ultrafast optics.