Fig. 1. Core morphology of untreated SiGe core fiber. (a) Cross section; (b) profile section

Fig. 2. Raman spectra corresponding to dark area and bright area of the fiber cross section

Fig. 3. Schematic of laser thermal processing

Fig. 4. Profile section of the treated fiber at scanning length of 8 mm and HEAT of 700

Fig. 5. Treated fiber at scanning length of 1.5 mm and HEAT of 700. (a) Later view of fiber with interface; (b) cross section of fiber in the left area of interface

Fig. 6. Raman spectra of dot A‒J. (a) Dot A‒E; (b) dot F‒J

Fig. 7. Later view of the treated fiber at scanning length of 1.5 mm and HEAT of 500

Fig. 8. Cross section of fiber core after end-face polishing at center of Fig.7

Fig. 9. Schematic of solidification process corresponding to edge melt with different laser scanning lengths

Fig. 10. Schematic of indefinite interval polishing

Fig. 11. Cross section of the fiber after directional polishing