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At present, only KBe2BO3F2 (KBBF) can effectively realize a deep‐ultraviolet (DUV) coherent output, while the layered growth habit seriously hinders its application. Here, a new design strategy with an optimized KBBF‐like structure based on the quasi‐phase matching principle is proposed. Thus, the first KBBF‐like ferroelectric, Li2KRb(SO4)2, is designed. It exhibits a short DUV absorption cutoff edge of 163 nm, a large nonlinear optical (NLO) effect of 1.7 × KH2PO4 under a 1064 nm laser, and typical ferroelectricity. More importantly, it completely eliminates the layered structure by replacing K‐F bonds with strong ‐Li‐O‐S‐ ones as the interlayer force. Therefore, this work finds a new promising DUV NLO candidate, a unity of the DUV transparency, NLO response, and ferroelectricity, which is advantageous to explore new DUV NLO materials. [ABSTRACT FROM AUTHOR]

Owing to the vital role of birefringent materials in various advanced optical systems, it is very important to find and design structures with a large birefringence. Thus, the LaBO3 crystal was investigated. It exhibits a structural characteristic of quasi-two-dimensional [BO3] layers formed by separate [BO3] groups, which leads to a moderate birefringence (0.093@546 nm). Besides, the LaBO3 crystal presents a short ultraviolet absorption cutoff of 237 nm corresponding to the band gap of 5.23 eV (the calculated value of 4.81 eV). Remarkably, the LaBO3 crystal possesses a large transparency window with a transmittance of more than 60% in the region of 300–2000 nm. Therefore, this study points out a promising birefringent crystal and further confirms a favorable structure of the quasi-two-dimensional [BO3] layer to a large birefringence, which could facilitate the design of new ultraviolet and deep-ultraviolet birefringent crystals. [ABSTRACT FROM AUTHOR]

Nonlinear optical crystals with ferroelectricity, which could realize ultraviolet/deep‐ultraviolet coherent output by the quasiphase matching technology, are expected to be promising candidates for the new type of ultraviolet/deep‐ultraviolet nonlinear optical materials. Here, a new borosilicate crystal, LaBSiO5, is found, which is superior to the famous commercial quasiphase matching crystals, LiNbO3, KTiOPO4, and LaBGeO5 in performances. LaBSiO5 crystal exhibits excellent optical and electrical properties, including a short absorption cutoff (186 nm), a moderate second‐harmonic generation response (≈1.1 × KH2PO4), and the ferroelectric polarization reversal (coercive field ≈ 36.98 kV cm−1, remnant polarization ≈ 1.83 µC cm−2). Besides, no layering tendency is found during the process of crystal growth. Therefore, LaBSiO5 crystal is a potential ultraviolet quasiphase matching material. [ABSTRACT FROM AUTHOR]

Antiperovskites have been studied since the 1980s because of their rich physical and chemical properties, but their linear and second-order nonlinear optical responses remain largely unknown. Here we report a new polar crystal, Cs 3 Cl(HC 3 N 3 S 3 ) (I), which features a quasi-one-dimensional antiperovskite structure composed of ClCs 6 polyhedra and A-site [HC 3 N 3 S 3 ] 2- rings. To our best knowledge, this kind of antiperovskite structure is reported for the first time. Remarkably, I exhibits a very strong nonlinear optical response up to 11.4 times that of the benchmark KH 2 PO 4 and exceptionally large birefringence of 0.52. The first-principles calculations and structural analyses reveal that [HC 3 N 3 S 3 ] 2- is the "material gene" while the antiperovskite structural feature making it in a favorable arrangement. This work provides a new structural platform for the rational design of integrated optoelectronic materials with linear and second-order nonlinear optical responses., (© 2022 Wiley-VCH GmbH.)

It remains a challenge to develop UV nonlinear optical (NLO) crystals that can achieve a desirable trade-off on UV absorption edge, second harmonic generation (SHG), and birefringence. Here we report a thiosulfate UV NLO crystal of a 2D van der Waals layered structure, [C(NH 2 ) 3 ] 2 SO 3 S. Remarkably, this thiosulfate realizes the desired trade-off, with a short absorption edge of 254 nm, a strong SHG response of approximately 2.8 times that of the benchmark KH 2 PO 4 , and a sufficient birefringence of 0.073 at the wavelength of 546 nm. In addition, it exhibits strong in-plane anisotropy of the SHG intensity. According to the first-principles calculations, the non- π -conjugated [SO 3 S] 2- anion is the dominant SHG functional gene, while the π -conjugated [C(NH 2 ) 3 ] + cation serves as the functional gene of birefringence. This is different from common UV NLO materials whose functionals of SHG and birefringence are the same. These findings indicate that combining different function genes may be an effective strategy to develop outstanding NLO materials with the desirable property trade-off.

Nonlinear optical crystals play important roles in modern laser science and technology. However, the design and growth of new nonlinear optical (NLO) materials is still a challenging issue for researchers. Due to the excellent performance of Mg 3 B 7 O 13 Cl crystal, we paid attention to the optimization of its structure, in order to find new NLO materials with favorable properties. Here, Zn 3 B 7 O 13 Cl crystals were obtained by a high-temperature solution method. Its structure was determined to be the trigonal symmetry with a polar space group of R 3 c , which is more highly symmetric than that of Mg 3 B 7 O 13 Cl ( Pca 2 1 ). The experimental and theoretical investigations demonstrated that the title compound exhibits a short absorption cutoff (band gap ∼6.53 eV), moderate SHG responses (2.2 times that of KDP at 1064 nm), and the improved birefringence, which results from the large distortion and anisotropy of borate groups and zinc polyhedrons. Therefore, the structural modification of Mg 3 B 7 O 13 Cl by zinc cations achieves a balance between the deep-ultraviolet transparency, the nonlinear optical effect, and the moderate birefringence, which is very significant for the design of practical NLO materials.

M 2 B 5 O 9 X is a prominent family with excellent nonlinear optical (NLO) responses, just as the Pb 2 B 5 O 9 I crystal with a large second harmonic generation (SHG) of 13.5 times that of KH 2 PO 4 . However, most of these compounds are limited to ultraviolet and visible regions because of their long absorption edge (small band gap). Here, we report two members of this family, which change the situation. Using a high-temperature solution method, we obtain Ca 2 B 5 O 9 Cl and Sr 2 B 5 O 9 Cl crystals, which exhibit a deep-ultraviolet (DUV) absorption edge of 170 nm (band gap ≈ 7.29 eV). It is an important breakthrough in the DUV transparency of the M 2 B 5 O 9 X family. Furthermore, Ca 2 B 5 O 9 Cl crystals display a phase-matching SHG response under a 1064 nm laser, which is further confirmed by the balance between the suitable birefringence and the small dispersion of refractive indexes in the wavelength range of 1064-532 nm. Therefore, they are promising DUV transparency windows and NLO candidates.