Work

From [Ba3S][GeS4] to [Ba3CO3][MS4] (M = Ge, Sn): Enhancing optical anisotropy in IR birefringent crystals via functional group implantation

Year: 2024

Type: article

Abstract: Birefringent crystals are crucial for manipulating light's phase and polarization, making them vital components in various optical devices. Traditionally, strategies for designing high-performance birefringent crystals have focused on modifying the parent structure. However, there are limited examples demonstrating how changing functional groups can effectively enhance birefringence (Δ n ), as such changes often significantly alter the crystal structure. In this study, we propose a “functional group implantation” strategy aiming at significantly improving birefringent performance within the chalcogenide system. This involves replacing the isotropic [S] 2 – ions with anisotropic π-conjugated [CO 3 ] 2– groups. We validated this approach through comprehensive comparisons between the chalcogenide [Ba 3 S][GeS 4 ] and oxychalcogenide [Ba 3 CO 3 ][MS 4 ] (M = Ge and Sn), both of which adopt the same space group and feature the same arrangements of functional groups. Experimental characterization and theoretical calculations confirm that the [CO 3 ] 2 – groups exhibit significantly greater polarization anisotropy than the [S] 2 – groups. This difference leads to a marked increase in Δ n in [Ba 3 CO 3 ][MS 4 ] (ranging from 0.088 to 0.112 at 546 nm) compared to [Ba 3 S][GeS 4 ] (0.021 at 546 nm). This finding not only broadens the structural chemistry of π-conjugated chalcogenides but also illustrates the potential of functional group implantation for designing infrared birefringent crystals with enhanced optical anisotropy. A functional group implantation strategy was proposed to significantly enhance the birefringent performance by replacing isotropic [S] 2 ⁻ ions in the chalcogenide [Ba₃S][GeS₄] with anisotropic π-conjugated [CO₃] 2 ⁻ groups in the oxychalcogenide [Ba₃CO₃][MS₄] (M = Ge and Sn). This implantation of functional groups does not alter the overall structure; however, both optical anisotropy and birefringence are greatly improved.

Source: Chinese Journal of Structural Chemistry

DOI: 10.1016/j.cjsc.2024.100455

Authors: Yong-Fang Shi, Sheng-Hua Zhou, Zuju Ma, Xin-Tao Wu, Hua Lin, Qi-Long Zhu