Stabilized single longitudinal mode fibre ring laser based on an inline dual taper Mach Zehnder interferometer filter coated with graphene oxide

This paper describes a proposal and experimental demonstration of a narrow single longitudinal mode fibre ring laser with high power efficiency and a simple setup. A single longitudinal mode filter was realized by depositing graphene oxide flakes on a dual fibre taper Mach Zehnder interferometer in a loop mirror, wherein the loop structure acted as a passive narrowband reflector with the ability to generate a stable single longitudinal mode. This filter incorporation allowed for the generation of a single longitudinal mode having a side mode suppression ratio of 75 dB at 60 mW pump power and a 3 dB line width of 0.16 nm which is limited by the optical spectrum analyzer resolution.