Fig. 1. The fusion splicer geometry. Two variable parameters, gap/overlap and offset, determine the position of the fibers with respect to the electrode axis.

Fig. 2. The relative loss with respect to the butt-coupled transmission from the SMF to the 10.9 µm PBGF during the fusion procedure. The gap curve is estimated from the splice parameters, the Ericsson FSU-995-FA fusion splicer manual, and the relative loss curve. The values in parenthesis indicate altered parameters for new electrodes.

Fig. 3. A micrograph showing the splice between the SMF and 10.9 µm PBGF. Picture courtesy of the GaN Group in the Kansas State University Physics Department.

Fig. 4. Chamber used to evacuate and fill the PBGF with acetylene gas for saturated absorption spectroscopy.

Fig. 5. Saturated absorption spectra in (a) 10.9 µm and (b) 20 µm diameter PBGFs. Fiber 1 is 0.78 m long, spliced to SMF using a conventional arc splicer using the technique described in this paper. The P(11) spectrum was taken at 29 mW and 0.9 torr. Fiber 2 is 2.0 m long, spliced to SMF by Crystal Fibre A/S using a filament heating splicer, and its spectrum is taken of the weaker P(12) transition at 17 mW and 0.8 torr. Fiber 3 is the unspliced 10.9 µm fiber of 0.9 m long, the P(11) spectrum was taken at 30 mW of pump power at 0.6 torr. Fiber 4 is 0.4 m long, spliced with an arc splicer to SMF, the P(11) spectrum was taken at 34 mW and 0.9 torr. Fiber 5 is unspliced fiber 0.78 m long, and the P(11) spectrum was taken at 29 mW of pump power at 0.7 torr.