An Effective Strategy for Designing Nonlinear Optical Crystals by Combining the Structure‐Directing Property of Oxyfluorides with Chemical Substitution

Abstract

Rationally designing a high‐performance nonlinear optical (NLO) crystal remains a great ongoing challenge. It involves not only the design of noncentrosymmetric structures but also property optimization. In this communication, a new strategy for effectively designing the NLO crystal has been put forward, that is, using the structure‐directing property of oxyfluoride anions to obtain a noncentrosymmetric and polar structure, and then by substitution of IO3− for isovalent F− anions to further enhance the SHG response. With this strategy, a new iodate fluoride, Ba2[MoO3F(IO3)](MoO3F2) has been successfully designed from the Ba2(MoO3F2)F2 with the cis‐directing [MoO4F2]4− groups. It exhibits a large SHG response (≈8×KDP), a wide transparent region (0.30–10.92 μm), a high laser‐induced damage threshold (LDT) (88.53 MW cm−2), and a large birefringence (≈0.264@532 nm). These indicate Ba2[MoO3F(IO3)](MoO3F2) would be a promising NLO crystal.

Ba2[WO3F(IO3)][WO3F2]: the first polar fluorinated tungsten iodate featuring a direct W–O–I bond

“…The compound is iso-structural with Ba 2 [MoO 3 F(IO 3 )](MoO 3 F 2 ) previously reported by our group. 36 1), 2.08; Ba(2), 1.77; W(1), 6.21; W(2), 5.94; and I(1), 5.01, which are consistent with their expected valences (Ba, 2.00; W, 6.00; I, 5.00).…”

“…The compound is iso-structural with Ba 2 [MoO 3 F(IO 3 )](MoO 3 F 2 ) previously reported by our group. 36 Interestingly, the substitution positions of F are different between W- and Mo-based octahedra, resulting in different NLO properties. Performance measurements show that Ba 2 [WO 3 F(IO 3 )][WO 3 F 2 ] has a large SHG response (3.5 × KH 2 PO 4 , KDP), wide visible and mid-infrared transparency region (0.28–10.74 μm), and a moderate birefringence of 0.061@532 nm.…”

Cs2VOF4(IO2F2): Rationally designing a noncentrosymmetric early-transition-metal fluoroiodate

“…F − anions are coordinated with not only ETM cations but also I 5+ cations, and the structures contain I–F bonds). 51–54 Most previously reported F-containing ETM iodates are ETM iodate-fluorides, and research on ETM fluoroiodates is still rare. In particular, how to rationally synthesize ETM fluoroiodates is still unknown.…”

Ultrawide Bandgap and Outstanding Second‐Harmonic Generation Response by a Fluorine‐Enrichment Strategy at a Transition‐Metal Oxyfluoride Nonlinear Optical Material

“…One effective strategy to develop efficient NLO materials is to introduce stereochemically‐active lone‐pair cations (e.g. I 5+ , Se 4+ and Te 4+ ) [11] into oxyfluorides, relevant examples including α‐/β‐Ba 2 [VO 2 F 2 (IO 3 ) 2 ](IO 3 ), [11a] Ba 2 [MoO 3 F(IO 3 )](MoO 3 F 2 ), [11b] Cs(TiOF) 3 (SeO 3 ) 2 , [11c] and RbTeMo 2 O 8 F [11d] . Nevertheless, the as‐prepared fluorinated TM iodates/selenites/tellurites and all TM‐centered oxyfluorides have relatively small band gaps ( E g <4.42 eV), and are thus not suitable for use in the solar‐blind UV, due to the d orbitals and corresponding transitions of the TM cations.…”