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Acid intercalation-exfoliated 2D Bi shows strong nonlinear NIR responses associated with multi-timescale carrier dynamics and is used for mode-locking lasers.

Liquid-phase exfoliated 2D material multilayer MoS 2 is transferred onto a gold mirror and its saturable absorption at the 2 µm wavelength region is experimentally observed. This transferred MoS 2 saturable absorber has a modulation depth of 13.6% and a saturation intensity of 23.1 MW cm −2 . This saturable absorber is integrated into a linear Tm 3+ fiber laser cavity, and stable fundamental-frequency mode-locking operation is realized at 2 µm with pulse energy of 15.5 nJ, pulse width of ~843 ps, and a repetition rate of 9.67 MHz. The laser spectral width is ~17.3 nm with a center wavelength of 1905 nm. This first presence of modelocking with multilayer MoS 2 sheets in the 2 µm wavelength region verifies that multilayer MoS 2 is a good candidate for broadband mode-locking comparable to graphene, as well as a good mode-locker for achieving high pulse energy.

We briefly review the development of gain-switched rare-earth-doped fiber lasers and their applications in wavelength conversion to mid-IR, supercontinuum generation, and medicine in recent years. We illustrate the similarities between gain-switching and Q-switching techniques that will provide tools for the design and optimization of the gain-switched fiber lasers. From the nature of the gain-switched fiber lasers, benefits of this kind of lasers to 2-μm region and in-band-pumped (two-level system) laser systems are obvious. Advantages of in-band-pumped 2-μm lasers are discussed and analyzed with a simple numerical simulation in terms of Tm-doped fiber lasers. We also propose the key factors in the development of the gain-switched fiber lasers and predict the future tendency.