The main commercially used birefringent oxides a-BaB 2 O 4 and YVO 4 have the birefringences of 0.12 and 0.22. We propose atargeted high-throughput screening system to search birefringence-active functional modules (FMs) and large birefringent materials.Aseries of p-conjugated CÀOu nits 2À are discoveredt o be birefringence-active FMs.T heoretical and experimental studies on the crystals with C À Ounits confirm the feasibility of strategy.B ased on this,t he CÀOc ontaining compounds ranging from deep-ultraviolet to near-infrared region with large birefringence from 0.1 to 1.35 are found, and most of them break through the birefringent limit of oxides.T he (NH 4 ) 2 C 2 O 4 •H 2 Oc rystal is grown and its experimental birefringence is 0.248 at 546 nm, which is identified as apromising UV birefringent crystal. The A-site cations playsignificant roles in optical properties by influencing the density and arrangement of the CÀOunits.

By the selective fluorination of IO 4 in iodates, SrI 2 O 5 F 2 (SIOF) and Ba(IO 2 F 2 ) 2 (BIOF) were synthesized successfully. They are the first reported cases of alkaline-earth metal fluoroiodates, and the (IO 3 F) 2− units in SIOF were discovered for the first time to the best of our knowledge. BIOF possesses the shortest UV cutoff edge (230 nm), and SIOF has the largest birefringence (cal. 0.203 at 532 nm) among the reported fluoroiodates. The highly polarizable (IO 3 F) 2− , with high polarizability anisotropy, induces a large birefringence in SIOF by theoretical calculation. This work will contribute to enlarge the structural diversity and provide a good choice for the material design in fluoroiodates.

The first zinc iodate fluoride, ZnIO 3 F, was synthesized by the Zn 2+ cation, the IO 3 group, and fluorine ion, where Zn 2+ is coordinated by O atoms from iodate and F atoms to form the ZnO 4 F 2 polyhedron. It has outstanding optical characteristics, including large birefringence (Δ = 0.219 at 546 nm), wide band gap (E g = 4.2 eV), and good thermal stability (over 475 °C), showing a subtle balance between the wide band gap and birefringence.

The exploration of novel infrared nonlinear optical (IR NLO) materials with large second-harmonic generation (SHG) responses and wide band gaps has become very imperative recently. Herein we reported two noncentrosymmetric compounds, LiBa4Ga5Q12 (Q = S, Se), crystallizing in space group P 21 c (No. 114), which feature 3D frameworks built by a basic [Ga5Q16]17– windmill cluster and LiQ4 tetrahedra in a cesium chloride topological structure. Both compounds satisfy the desired balance between good SHG responses (∼1.5× that of AgGaS2) and wide band gaps (3.43 and 2.44 eV) with remarkable laser damage thresholds (21× and 6× that of AgGaS2). The theoretical calculations uncover that the [Ga5Q16]17– cluster makes major contributions to the SHG effect in LiBa4Ga5Q12. In addition, the structure–performance relationship among all compounds in the I–II4–III5–VI12 system has been discussed systematically, which indicates that the introduction of the alkali metal lithium in the I site is beneficial for the production of large band gaps. This work will be helpful in exploring novel IR NLO materials with special structures and comprehensive properties in the chalcogenide system.

A new centimetre-scale fluorooxoborate crystal Ba(B2OF3(OH)2)2, with well-ordered OH/F units and a new dimer containing BOF3 units, has been fabricated.

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Ultrafast laser micromachining provides many advantages for precision micromachining. One challenging problem, however, particularly for multilayer and heterogeneous materials, is how to prevent a given material from being ablated, as ultrafast laser micromachining is generally material insensitive. We present a real-time feedback control system for an ultrafast laser micromachining system based on laser-induced breakdown spectroscopy (LIBS). The characteristics of ultrafast LIBS are reviewed and discussed so as to demonstrate the feasibility of the technique. Comparison methods to identify the material emission patterns are developed, and several of the resulting algorithms were implemented into a real-time computer control system. LIBS-controlled micromachining is demonstrated for the fabrication of microheater structures on thermal sprayed materials. Compared with a strictly passive machining process without any such feedback control, the LIBS-based system provides several advantages including less damage to the substrate layer, reduced machining time, and more-uniform machining features.

Perovskite-related compounds are of vital significance in the optical element and laser industry and other fields. Exploring the contributions of microscopic units that form the perovskite framework is one efficient way to design new materials with targeted performance. In this work, we acquired the linear and nonlinear optical properties and analyzed the superior functional units in determining optical anisotropy and second harmonic generation (SHG) of typical perovskite-related compounds from inorganic to organic, namely