In recent years, 2D layered materials, including graphene, topological insulators, transition metal dichalcogenides, black phosphorus, MXenes, graphitic carbon nitride, and metal‐organic frameworks, have attracted considerable interest due to their potential applications in the fields of physics, chemistry, biology, and energy. Their rise in the field of nonlinear photonics began around 2009 and has become an important research direction. Here, the synthesis techniques, nonlinear optical properties, integration strategies, and device applications of layered materials are reviewed. In terms of nonlinear optical properties, the focus is on saturable absorption and Kerr nonlinearity. On this basis, their applications in various pulsed lasers, including fiber lasers, solid‐state lasers, waveguide lasers, and related nonlinear optical phenomenon, are summarized. In addition, novel optical devices using layered materials, such as optical modulators, optical polarizers, optical switchers, and even all‐optical device, are also involved. It is believed that the development of 2D layered materials in the field of photonics will continue to deepen, thus laying a good foundation for its practical application.

Few-layer bismuthene is an emerging two-dimensional material in the fields of physics, chemistry, and material science. However, its nonlinear optical property and the related photonics device have been seldom studied so far. Here, we demonstrate a sub-200 fs soliton mode-locked erbium-doped fiber laser (EDFL) using a microfiber-based bismuthene saturable absorber for the first time, to the best of our knowledge. The bismuthene nanosheets are synthesized by the sonochemical exfoliation method and transferred onto the taper region of a microfiber by the optical deposition method. Stable soliton pulses centered at 1561 nm with the shortest pulse duration of about 193 fs were obtained. Our findings unambiguously imply that apart from its fantastic electric and thermal properties, few-layer bismuthene may also possess attractive optoelectronic properties for nonlinear photonics, such as mode-lockers, Q-switchers, optical modulators and so on.

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The combination of 2D materials and optical biosensors has become a hot research topic in recent years. Graphene, transition metal dichalcogenides, black phosphorus, MXenes, and other 2D materials (metal oxides and degenerate semiconductors) have unique optical properties and play a unique role in the detection of different biomolecules. Through the modification of 2D materials, optical biosensor has the advantages that traditional sensors (such as electrical sensing) do not have, and the sensitivity and detection limit are greatly improved. Here, optical biosensors based on different 2D materials are reviewed. First, various detection methods of biomolecules, including surface plasmon resonance (SPR), fluorescence resonance energy transfer (FRET), and evanescent wave and properties, preparation and integration strategies of 2D material, are introduced in detail. Second, various biosensors based on 2D materials are summarized. Furthermore, the applications of these optical biosensors in biological imaging, food safety, pollution prevention/control, and biological medicine are discussed. Finally, the future development of optical biosensors is prospected. It is believed that with their in-depth research in the laboratory, optical biosensors will gradually become commercialized and improve people's quality of life in many aspects.

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