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
Finding crystals with high birefringence(Δn),especially in deep-ultraviolet(DUV)regions,is important for developing polarization devices such as optical fiber sensors.Such materials are usually discovered using experimental techniques,which are costly and inefficient for a large-scale screening.Herein,we collected a database of crystal structures and their optical properties and trained atomistic line graph neural network to predict theirΔn.To estimate the level of confidence of the trained model on new data,D-optimality criterion was implemented.Using trained graph neural network,we searched for novel materials with highΔn in the Materials Project database and discovered two new DUV birefringent candidates:NaYCO_(3)F_(2) and SClO_(2)F,with highΔn values of 0.202 and 0.101 at 1064 nm,respectively.Further analysis reveals that strongly anisotropic units with various anions andπ-conjugated planar groups are beneficial for highΔn.
Ivan A.KruglovLiudmila A.BereznikovaCongwei XieDongdong ChuKe LiEvgenii TikhonovAbudukadi TudiArslan MazitovMin ZhangShilie PanZhihua Yang
A high-birefringence fiber,Tb:YAG crystal-derived silica fiber(TYDSF),was fabricated by CO_(2)laser-heating drawing technique.Its linear birefringence was 2.99×10^(-5),and it was used to fabricate an all-fiber quarter-wave plate(QWP)device.The polarization extinction ratio(PER)of the device was 0.29 dB,and its ellipticity was 44.26°at 25℃.In the temperature range of-5℃to 200℃,its PER was always less than 0.80 dB,and the fluctuation of PER and ellipticity was also small.Compared with QWPs fabricated with PANDA-type polarization-maintaining fiber(PMF)and elliptical-core PMF,the performance of TYDSF QWP was least sensitive to temperature.Furthermore,the TYDSF QWP was used in a high-power laser system,still maintaining good circular polarization state,and the nonlinear effects were suppressed in the system.The experimental results are of great significance to high-power lasers,fiber-optic current sensors,etc.,in harsh environments.
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
An organic-inorganic hybrid antimony(Ⅲ)oxalate(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]has been successfully obtained by simultaneous combination of a-conjugated 4-hydroxypyridine and(C_(2)O_(4))^(2-)group with stereochemical active Sb(Ⅲ)cation.The compound features a layered structure,and the equatorial planes of SbO6 units,π-conjugated(C_(2)O_(4))^(2-)and(C5H6ON)+groups are closer to a planar arrangement,representing strong structural anisotropy that favors a large birefringence.As expected,(C_(5)H_(6)ON)_(2)[Sb_(2)O(C_(2)O_(4))_(3)]exhibits a large birefringence of 0.279 at 546 nm.Structural and theoretical analyses indicate that the combination of multipleπ-conjugated units is a feasible approach for designing and exploring new superior birefringent materials.
Switching of light polarization on the sub-picosecond timescale is a crucial functionality for applications in a variety of contexts,including telecommunications,biology and chemistry.The ability to control polarization at ultrafast speed would pave the way for the development of unprecedented free-space optical links and of novel techniques for probing dynamical processes in complex systems,as chiral molecules.Such high switching speeds can only be reached with an all-optical paradigm,i.e.,engineering active platforms capable of controlling light polarization via ultrashort laser pulses.Here we demonstrate giant modulation of dichroism and birefringence in an all-dielectric metasurface,achieved at low fluences of the optical control beam.This performance,which leverages the many degrees of freedom offered by all-dielectric active metasurfaces,is obtained by combining a high-quality factor nonlocal resonance with the giant third-order optical nonlinearity dictated by photogenerated hot carriers at the semiconductor band edge.
Giulia CrottiMert AkturkAndrea SchiratoVincent VinelAnton A.TrifonovIvan C.BuchvarovDragomir N.NeshevRemo Proietti ZaccariaPaolo LaportaAristide LemaîtreGiuseppe LeoGiulio CerulloMargherita MaiuriGiuseppe Della Valle
