Hexagonal boron nitride (hBN) is one cute material in two- and multiphoton absorption, photoluminescent and hyperbolic phonon-polariton application due to its excellent electronic properties. However, current experimental studies of hBN nonlinear optical characteristics are still at initial stage. In order to have a comprehensive understanding of its nonlinear optical, thermo- and acousto-optical properties, it becomes urgent to explore into its interaction with laser.
Recently, a collaborative study led by Prof. WANG Jun at Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, investigated the character of stimulated Brillouin scattering (SBS) and two-photon absorption (2PA) of hBN flake suspensions.
The layered hBN nanosheets were prepared by using liquid-phase exfoliation technique in N-methyl-2-pyrrolidone (NMP). The obtained BN structure was studied through transmission electron microscopy, micro-Raman analysis and UV/VIS/NIR spectrometer. Optical limiting and SBS measurements were performed with Continuum Minilite II laser source at 532 nm. Measuring the 2PA cross-section σ2PA and Brillouin gain factor gB of hBN suspension, researchers found that SBS exhibited a significant quenching with hBN concentration, just as the result previously observed in graphene suspension .
In addition, the 2PA cross-section is so large that the BN nanoflakes can absorb enough energy to be heated up to the melting temperature. Quenching in case of BN could be attributed to the acoustic attenuation increase owing to the melting of BN and nanoflakes-into-nanodrops transformation under the laser beam at intensities above the SBS threshold.
Since BN dispersed in a liquid with the concentrations is highly transparent for low-intensity irradiation, it can be recommended as an appropriate dopant for the design of nonlinear-optical composites for all-optical filters, as well as transparent materials with the SBS suppression. The BN suspension is also an interesting model system for studying nonlinear optical and acousto-optical phenomena.
This study, entitled “Competition between stimulated Brillouin scattering and two-photon absorption in dispersed boron nitride” has been published online by Optics Express on April 4, 2019.
This work was supported by the Chinese National Natural Science Foundation, the Strategic Priority Research Program of CAS, the Key Research Program of Frontier Science of CAS, the Program of Shanghai Academic Research Leader and President’s International Fellowship Initiative of CAS.
Figure 1. Two-photon absorption and stimulated Brillouin scattering performance in dispersed boron nitride.(Image by SIOM)
 I. M. Kislyakov, J. M. Nunzi, X. Y. Zhang, Y. F. Xie, V. N. Bocharov, and J. Wang, Stimulated brillouin scattering in dispersed graphene, Optics Express 26, 34346 (2018).
Mr. Cao Yong
General Administrative Office
Shanghai Institute of Optics and Fine Mechanics, CAS