Graphene-decorated microfiber knot as a broadband resonator for ultrahigh-repetition-rate pulse fiber lasers

Searching for an ultrahigh-repetition-rate pulse on the order of hundreds of gigahertz (GHz) is still a challenging task in the ultrafast laser community. Recently, high-quality silicon/silica-based resonators were exploited to generate a high-repetition-rate pulse based on the filter-driven four-wave mixing effect in fiber lasers. However, despite their great performance, the silicon/silica-based resonators still have some drawbacks, such as single waveband operation and low coupling efficiency between the fiber and resonators. To overcome these drawbacks, herein we proposed an all-fiber broadband resonator fabricated by depositing the graphene onto a microfiber knot. As a proof-of-concept experiment, the graphene-deposited broadband microfiber knot resonator (MKR) was applied to Er- and Yb-doped fiber lasers operating at two different wavebands, respectively, to efficiently generate hundreds-of-GHz-repetition-rate pulses. Such a graphene-deposited broadband MKR could open some new applications in ultrafast laser technology, broadband optical frequency comb generation, and other related fields of photonics.