As a fundamental parameter of the optical crystals,birefringence plays a vital role in many optical applications,such as phase modulation,light splitting,and polarization,especially the phase matching process of the nonlinear optical crystals.The big birefringence not only benefits to the miniaturization of related devices,but also broadens the phase-matching wavelength range of nonlinear optical crystals.The design and synthesis of crystals with large birefringence becomes a hot research topic due to its more and more important applications in the optical modulation and laser technology fields.Herein,crystals with birefringence greater than 0.05 in the borate system are reviewed and classified according to different birefringent active groups,and the relationship between structure and properties is thoroughly explored.It is hoped that this review will provide a clear understanding of what kinds of building units and arrangements would have more opportunity to get adequate birefringence in borate systems and provide the statistical references to encourage the emergence of better crystal materials with large birefringence.
Qianzhen ZhangRan AnZhihua YangXifa LongShilie PanYun Yang
Herein,two antimony sulfates,named RbSb(SO_(4))_(2)(1)and CsSb(SO_(4))_(2)(2),have been successfully synthesized with the introduction of Sb^(3+)cation with stereochemically active lone pairs(SCALP)into sulfates by the conventional hydrothermal method.Both two compounds endow short ultraviolet(UV)absorption edges(281 nm and 278 nm,respectively)and large birefringence(0.171@546 nm and 0.174@546 nm,respectively),which means that they are promising short-wave UV optical materials.Interestingly,though both of the two compounds exhibit similar 1D chained structures,and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups,they exhibit significantly opposite macroscopic symmetries,i.e.,compound 1 crystallizes in a centrosymmetric(CS)manner(P2_(1)/n)and compound 2 in a noncentrosymmetric(NCS)manner(P2_(1)2_(1)2_(1)),due to the size of cations[r(Rb+)=1.56 A˚,r(Cs+)=1.67 A˚]affects the orientation of SCALP of the adjacent Sb^(3+).
Yang LanJinxuan RenPu ZhangXuehua DongLing HuangLiling CaoDaojiang GaoGuohong Zou
