Fig. 1. Spectroscopic gas sensing system based on FTIR and hollow waveguide

Fig. 2. Fingerprint absorption of gases and typical loss spectra of waveguides. (a) Normalized absorption coefficient; (b) loss spectra of waveguides

Fig. 3. Typical loss spectra of PI/Ag, FCP/Ag, and PS/Ag hollow waveguides

Fig. 4. Schematic diagram of sample gas preparation by bubbling method

Fig. 5. Standard absorption of HN₃ and loss spectra of hollow waveguides before and after injecting HN₃ sample gas. (a) Ag waveguide; (b) AgI/Ag waveguide; (c) SiO₂/Ag waveguide; (d) COP/Ag waveguide

Fig. 6. High resolution loss spectra of Ag waveguide filled with wet HN₃ gas

Fig. 7. Loss spectra of hollow waveguides with HCl sample gas, and standard absorption of HCl is added for comparison in the insets. (a) AgI/Ag waveguide; (b) Ag waveguide

Fig. 8. Original loss spectra and loss spectra of the hollow waveguide before and after importing the HCl sample gas. (a) AgI/Ag waveguide; (b) Ag waveguide

Fig. 9. Absorption spectrum of cyclohexane volatiles