Fig. 1. Schematic diagram of thulium-doped fiber laser intracavity gas sensing system

Fig. 2. Physical map of thulium-doped fiber laser intracavity gas sensing system

Fig. 3. Simulate and experimental ASE spectra of the TDF

Fig. 4. Output spectrum of thulium-doped fiber lasers at different pump powers

Fig. 5. Detailed spectrum of output laser from thulium-doped fiber lasers at different pump powers

Fig. 6. The output spectrum of thulium-doped fiber laser at 1 000 mW pump power with filter

Fig. 7. Output spectra measured by OSA over 60 min with 10 min interval near 1 945 nm

Fig. 8. Tunable range of thulium-doped fiber laser intracavity gas sensing system at 1 000 mW pump power

Fig. 9. Experimental， Lorentz fitting and simulate absorption spectrum of H₂O in the wavelength range of 1 928~1 938 nm