Shanghai Optoelectronics Co., Ltd. has achieved research on the nonlinear optical properties of two-dimensional nanomaterials
Due to its rich non-linear optical characteristics, such as two-photon absorption, saturation absorption, and anti-saturation absorption, two-dimensional materials have huge application potential in the fields of laser technology, optical information, and communications. In recent years, two-dimensional materials have also been widely used in light wave mixing and other aspects, which is very important for the production of short-wavelength, tunable laser sources. The characteristics of stimulated Brillouin scattering and nonlinear absorption have important effects in the field of laser and optoelectronic communications, but these effects in two-dimensional materials are still unclear. Recently, the research team of Wang Jun, a researcher of the Micro-nano Optoelectronics Functional Materials Laboratory at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, has made many advances in the research of nonlinear optical properties of two-dimensional nanomaterials.
The research team (international visiting scholar Ivan Kislyakov of the Chinese Academy of Sciences) systematically studied the stimulated Brillouin scattering behavior and energy characteristics of graphene nanosheets in NMP and aqueous solutions. The study found that the low concentration of graphene suspension has a 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. Through theoretical calculations, the influence of different thermodynamics, electro-optic and acousto-optic parameters on the Brillouin gain factor during the quenching process of stimulated Brillouin scattering was verified. During the formation of carbon bubbles, the bubble concentration and compressibility will change, and will determine the stimulated Brillouin scattering behavior; the effective bubble size is estimated, and the bubble characteristics on the nanosecond time scale can be studied in conjunction with acoustic absorption experiments. These research results can be used to suppress the generation of stimulated Brillouin scattering under certain circumstances, such as laser technology, optical communication network, etc. The research results were published in Optics Express [26, 34346 (2018)].
The research team systematically studied the stimulated Brillouin scattering and two-photon absorption characteristics of hexagonal boron nitride (hBN) nanosheet suspensions, and measured the two-photon absorption cross-section σ2PA and the Brillouin gain coefficient gB under the action of a 532nm laser. It was found that when the hBN concentration is low, the stimulated Brillouin scattering quenching effect is shown, which is consistent with the conclusion of the graphene suspension; and the two-photon absorption cross section is very large, so the BN nanosheets can absorb enough energy to Heat to the melting temperature. The quenching of stimulated Brillouin scattering in BN is mainly caused by the sound wave attenuation caused by the melting of BN and the conversion of nanosheets 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 a nonlinear optical composite material for all-optical filters and as a transparent material dopant with stimulated Brillouin scattering inhibition . BN suspension is also an interesting model system for studying nonlinear optics and acousto-optic phenomena. The research results were published in Optics Express [27, 11029 (2019)].
The research team also cooperated with Professor Sun Zhenyu's research group of Beijing University of Chemical Technology through liquid glass technology to develop a large number of high-quality lead iodide (PbI2) two-dimensional nanosheets. The resulting dispersion can maintain good stability within 30 days. The study of nonlinear optical characteristics found that PbI2 nanosheets have saturation absorption (SA) characteristics under 515nm femtosecond pulse and 532nm nanosecond pulse, and the SA response under 6ns pulse excitation is stronger than that under 340fs pulse excitation. The saturation absorption characteristics of PbI2 nanosheets are comparable to some two-dimensional perovskite, graphene, black phosphorus and molybdenum disulfide materials. Moreover, PbI2's high stability and low unsaturation loss make it have great application prospects in Q-switched, mode-locked lasers, photodetectors and other ultrafast optoelectronic devices. The research results have been published online in ACS Photonics [DOI: 10.1021 / acsphotonics.9b00122].
Related work is supported by projects from the Chinese Academy of Sciences, the Fund Committee and the Shanghai Science and Technology Commission.
Figure 1 Schematic diagram of the electrostriction-thermal expansion resistance effect of graphene suspension after irradiation and its influence on the quenching of stimulated Brillouin scattering.
Figure 2 Two-photon absorption and stimulated Brillouin scattering characteristics of boron nitride suspension.
Figure 3 The lattice structure and saturation absorption characteristics of PbI2 nanosheets.
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