Raman Mapping Characterization of All-Fiber CVD Monolayer Graphene Saturable Absorbers for Erbium-Doped Fiber Laser Mode Locking

We present a study on the characterization and quality evaluation of all-fiber chemical vapor deposition (CVD) graphene saturable absorber samples for Erbium-doped fiber laser (EDFL) mode locking. Optical fiber end faces covered by CVD graphene were analyzed by Raman spectroscopy, and classification criteria related to graphene Raman bands properties were adopted in order to evaluate samples quality. The analysis revealed that for all samples, the fiber core was 100% covered by graphene, with 88% average monolayer graphene coverage, and 82% low defect graphene coverage. Graphene samples were used as saturable absorbers in EDFL, and soliton-like pulses as short as 599 fs were generated, with average pulse duration of 620 ± 10 fs among all samples.