Progress in research on nonlinear optical properties of two-dimensional nanomaterials

Recently, Wang Jun, a researcher at the Micro-optical Optoelectronic Functional Materials Laboratory of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made many advances in the study of nonlinear optical properties of two-dimensional nanomaterials.

The research team (Ivan Kislyakov, Chinese international visiting scholar) systematically studied the stimulated Brillouin scattering behavior and energy properties of graphene nanosheets in NMP and aqueous solution. It is found that the low concentration of graphene suspension produces strong stimulated Brillouin scattering quenching effect due to no significant absorption, and there is a linear dependence between the stimulated Brillouin scattering threshold and the graphene absorption coefficient. The effects of different thermodynamic, electro-optic and acousto-optic parameters on the Brillouin gain factor during the quenching process of stimulated Brillouin scattering are verified by theoretical calculations. During the formation of carbon bubbles, the concentration and compression coefficient of the bubbles change, and the stimulated Brillouin scattering behavior is determined; the effective bubble size is estimated, and the bubble characteristics of the nanosecond time scale can be studied in combination with the sonic absorption experiment. These findings can be used to suppress stimulated Brillouin scattering in some cases, such as laser technology, optical communication networks, and the like. Relevant research results have been published on Optics Express.

The research team systematically studied the stimulated Brillouin scattering and two-photon absorption characteristics of a hexagonal boron nitride (hBN) nanosheet suspension, and measured the two-photon absorption cross-section σ2PA and Brillouin gain coefficient gB under the action of 532 nm laser. It was found that a significant stimulated Brillouin scattering quenching effect was observed at a lower hBN concentration, which is consistent with the conclusion of the graphene suspension; and the two-photon absorption cross section is very large, so the BN nanosheet can absorb enough energy to Heat to the melting temperature. The stimulated Brillouin scattering quenching in BN is mainly caused by the melting of BN and the attenuation of sound waves caused by the nanosheets being converted into nanodroplets when the laser energy is higher than the stimulated Brillouin scattering threshold. The BN dispersion studied in this paper has high transparency under low-intensity irradiation, so it can be used as an all-optical filter nonlinear optical composite material and a transparent material dopant with stimulated Brillouin scattering suppression. . BN suspension is also an interesting model system for studying nonlinear optical and acousto-optic phenomena. Relevant research results have been published on Optics Express.

In addition, the research team and Sun Zhenyu, a professor at Beijing University of Chemical Technology, collaborated to develop a large number of high-quality lead iodide (PbI2) two-dimensional nanosheets through liquid glass technology. The resulting dispersion can maintain good stability within 30 days. Nonlinear optical properties studies have found that PbI2 nanosheets have saturated absorption (SA) characteristics at 515 nm femtosecond pulse and 532 nm nanosecond pulse, and the SA response at 6 ns pulse excitation is stronger than the SA response at 340 fs pulse excitation. The saturated absorption properties of PbI2 nanosheets are comparable to certain two-dimensional perovskites, graphene, black phosphorus and molybdenum disulfide materials. Moreover, the high stability and low unsaturation of PbI2 make it a promising application for Q-switched, mode-locked lasers, photodetectors and other ultrafast optoelectronic devices. The research results have been published online at ACS Photonics.

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