Fig. 1. Screening of pretreatment procedures. (a) Absorption spectra and (b) dynamic light scattering (DLS) spectra of a 0.01 mg/mL SnSe2 aqueous solution with different pretreatments.

Fig. 2. (a), (b) HAADF-STEM images, (c) crystal model, (d)–(f) EDXS results of SnSe2 nanosheets pretreated with urea.

Fig. 3. (a)–(c) XPS profiles and (d) Raman spectrum of SnSe2 nanosheets.

Fig. 4. NOPs of SnSe2 SA devices at (a) 1.55 μm and (b) 2 μm.

Fig. 5. Schematic diagram of the typical mode-locked fiber laser (for EDFL or TDFL).

Fig. 6. Stable ultrashort pulse operation: (a) optical spectrum, (b) oscilloscope trace, (c) autocorrelation trace, and (d) frequency spectrum.

Fig. 7. Chaotic multiple pulse operation: (a) optical spectrum, (b) high-speed oscilloscope trace (inset: low-speed oscilloscope trace), (c) enlarged view of the selected dashed part in (b), and (d) statistical histogram.

Fig. 8. Evolution of chaotic multiple pulses.

Fig. 9. Intensity histograms of chaotic pulses at (a) 500 mW and (b) 600 mW.

Fig. 10. Chaotic multiple pulse operation at 200 mW: (a) optical spectrum, (b) high-speed oscilloscope trace, (c) enlarged view of the selected dashed part in (b), and (d) statistical histogram.

Fig. 11. Output performance of the TDFL with a SnSe2-deposited SA: (a) optical spectrum, (b) oscilloscope trace, (c) autocorrelation trace, (d) frequency spectrum, (e) relationship between pump power and output power, and (f) optical spectra with different hours.

Fig. 12. Graphical comparison of TDFL with different 2D materials.