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Nanocomposites of layered MoS2 and multi-walled carbon nanotubes (CNTs) with core-shell structure were prepared by a simple solvothermal method. The formation of MoS2 nanosheets on the surface of coaxial CNTs has been confirmed by scanning electron microscopy, transmission electron microscopy, absorption spectrum, Raman spectroscopy, and X-ray photoelectron spectroscopy. Enhanced third-order nonlinear optical performances were observed for both femtosecond and nanosecond laser pulses over a broad wavelength range from the visible to the near infrared, compared to those of MoS2 and CNTs alone. The enhancement can be ascribed to the strong coupling effect and the photoinduced charge transfer between MoS2 and CNTs. This work affords an efficient way to fabricate novel CNTs based nanocomposites for enhanced nonlinear light-matter interaction. The versatile nonlinear properties imply a huge potential of the nanocomposites in the development of nanophotonic devices, such as mode-lockers, optical limiters, or optical switches. [ABSTRACT FROM AUTHOR]

Ultrafast saturable absorption (SA) materials that are capable of blocking the optical absorption under strong excitation have extensive applications in photonic devices. This work presents core/shell colloidal quantum dots (CQDs) which have the quantized energy levels, excellent band gap tunability, and possess significant SA performance. When the band gap is close to the pump pulse energy, the CQDs show significant resonant SA response. At the same excitation conditions, the core/shell CQDs dispersions show better SA response than graphene dispersions, and comparable to the recently reported molybdenum disulfide. The carrier dynamics of the SA of the CQDs is analyzed systematically. The research has also found that the two-photon absorption of the CQDs show nearly cubic power law of the band gap, while the SA performance keeps almost the same in the nonresonant regime. Further, superior passive Q-switched laser behavior is observed using the CQDs as a saturable absorber. The results directly reveal the physical processes of this basic problem and broaden the applications of CQDs in photonic devices. [ABSTRACT FROM AUTHOR]

Nonlinear optical property of transition metal dichalcogenide (TMDC) nanosheet dispersions, including MoS2, MoSe2, WS2, and WSe2, was performed by using Z-scan technique with ns pulsed laser at 1064 nm and 532 nm. The results demonstrate that the TMDC dispersions exhibit significant optical limiting response at 1064 nm due to nonlinear scattering, in contrast to the combined effect of both saturable absorption and nonlinear scattering at 532 nm. Selenium compounds show better optical limiting performance than that of the sulfides in the near infrared. A liquid dispersion system based theoretical modelling is proposed to estimate the number density of the nanosheet dispersions, the relationship between incident laser fluence and the size of the laser generated micro-bubbles, and hence the Mie scattering-induced broadband optical limiting behavior in the TMDC dispersions. [ABSTRACT FROM AUTHOR]

The development of functional materials for laser protection is an extremely important research field for the safety and security of users. To achieve simultaneous protection against both pulsed and continuous wave (cw) or quasi-cw lasers, significant research effort has been invested into state-of-the-art broadband optical limiting (OL) materials and processes in an attempt to achieve some measure of protection from such laser beams in the past decades. As the first truly two-dimensional material, graphene is being considered as an ideal material for modern photonic, optoelectronic and electronic devices because of its fantastic physical properties. Graphene shows ultrafast carrier relaxation dynamics and ultra-broadband resonate nonlinear optical (NLO) response due to their extended π-conjugate system and the linear dispersion relation holding for their electronic band structure. Almost all types of graphene-based materials described in this review exhibit strong broadband OL response. The dominant limiting mechanism of graphene is nonlinear scattering, which is very effective in liquid suspensions rather than in solid state hosts. In contrast to the pure graphene, the solubilized graphene and its derivatives optically limits through nonlinear absorption mechanism, nonlinear scattering as well as the photoinduced electron transfer and/or energy transfer between graphene and organic/polymeric species. This review describes systematically the OL mechanisms and the recent achievements on the graphene-based functional materials (i.e., graphene nanostructures, graphene composites, and covalently modified graphene) for OL applications. The future major ongoing areas of effort have also been suggested. [ABSTRACT FROM AUTHOR]