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.

We report on the generation of Q-switched and Q-switched mode-locked (QML) pulses in an erbium-doped fiber ring laser by using a polyvinyl alcohol (PVA) -based gold nanorod (GNR) saturable absorber (SA). The PVA-based GNR SA has a modulation depth of ～4.8% and a non-saturable loss of ～26.9% at 1.5 μm. A Q-switched pulse train with a repetition rate varying from 18.70 to 39.85 kHz and a QML pulse train with an envelope repetition rate tuning from 20.31 to 31.50 kHz are obtained. Moreover, the lasing wavelengths of the Q-switched pulses can be flexibly tuned by introducing a narrow bandwidth, tunable filter into the laser cavity. The results demonstrate that the GNRs exhibit good optical performance and can find a wide range of applications in the field of laser technology.