[ABa₂Cl][Ga₄S₈] (A = Rb, Cs): Wide-Spectrum Nonlinear Optical Materials Obtained by Polycation-Substitution-Induced Nonlinear Optical (NLO)-Functional Motif Ordering

Abstract

Noncentrosymmetry (NCS) is a prerequisite for second-order nonlinear optical (NLO) materials. In this work, a new polycation-substitution-induced centrosymmetry (CS)-to-NCS transformation strategy was applied in CS RbGaS2, affording two novel NCS salt-inclusion chalcogenides: [ABa2Cl]­[Ga4S8] (A = Rb, 1; Cs, 2). Remarkably, they exhibit the key merits of both Vis and IR NLO candidates, including strong phase-matchable second harmonic generation intensities (10.4–15.3 × KH2PO4 at 1064 nm; 0.9–1.0 × AgGaS2 at 1910 nm), high laser-induced damage thresholds (11–12 × AgGaS2), and a wide transparent window. Their prominent NLO performances originate from the orderly packing of T2-supertetrahedral Ga4S10 motifs resulting from the template effect of acentric polycation [ClA2Ba3]7+. The CS-to-NCS transformation first realized by polycation-substitution-induced NLO-functional motif ordering provides an effective approach for designing new NLO materials.

Pb18O8Cl15I5: A Polar Lead Mixed Oxyhalide with Unprecedented Architecture and Excellent Infrared Nonlinear Optical Properties

“…Single‐crystal LDT measurement using a pulsed laser (1064 nm, 10 ns) indicates that Pb 18 O 8 Cl 15 I 5 has a high LDT of 255 MW cm −2 , which is 8.5 times greater than that of AgGaS 2 (30 MW cm −2 ). As the LDT of a material has a positive correlation with its band gap, [16] we deduced that the enhanced LDT of Pb 18 O 8 Cl 15 I 5 single crystal is mainly caused by its wider band gap.…”

“…Thus far, most investigations to develop high‐performance IR NLO materials have been mainly focused on chalcogenides by adopting classical materials as templates [10] . In fact, multiple strategies such as metal/polycation/anion group substitutions [11] produced a number of attractive candidates with the balanced performances, [12] which include Li 2 Ga 2 GeS 6 , [13] BaGa 4 S 7 , [14] Na 2 ZnGe 2 S 6 , [15] and [RbBa 2 Cl][Ga 4 S 8 ] [16] . However, the growths of large crystals with high quality are still challenging due to the inevitably harsh growth conditions for chalcogenides, which is a major obstacle for the materials’ practical application.…”

“…[10] In fact, multiple strategies such as metal/polycation/anion group substitutions [11] produced a number of attractive candidates with the balanced performances, [12] which include Li 2 Ga 2 GeS 6 , [13] BaGa 4 S 7 , [14] Na 2 ZnGe 2 S 6 , [15] and [RbBa 2 Cl]-[Ga 4 S 8 ]. [16] However, the growths of large crystals with high quality are still challenging due to the inevitably harsh growth conditions for chalcogenides, which is a major obstacle for the materials practical application. Meanwhile, metal halides have also been identified as a promising source because of their broad IR transparency, high LDTs, and facile crystal growth conditions.…”

“…The asymmetric unit contains eighteen crystallographic Pb, eight O, thirteen Cl, three I, and four mixed Cl/I sites, and all the crystallographic sites are fully occupied (Table S2 and Figure S4). Noticeably, Pb 2+ cations exhibit diverse coordination geometries with asymmetric features: Pb(1)-Pb (16) have mixed ligand coordination with x O 2À + m Cl À + n I À (x = 1-3), while Pb(17)-Pb (18) are only coordinated by halogen anions (Figure S5). Typically, the structure of Pb 18 O 8 Cl 15 I 5 can be illuminated from the viewpoint of anion-centered tetrahedra.…”

Recent Advances in Oxide‐based Nonlinear Optical Materials with Wide Infrared Transparency Beyond 6 μm

“…Dominantly, metal chalcogenides are the leading system for the explorations attributable to their large NLO coefficients and the proven possibility to achieve balanced condition between the band gap and SHG response [18] . By adopting multiple design and synthetic strategies, [19] such as various chemical substitutions, multiple NLO‐functional motifs combinations, and CS‐to‐NCS modifications, many chalcogenides revealing excellent comprehensive properties, such as LiGaSe 2 , [20] LiInS 2 , [20,21] BaGa 4 S 7 , [22] BaGa 4 Se 7 , [23] BaGa2GeS6, [24] Na 2 ZnGe 2 S 6 , [25] Li 2 Ga 2 GeS 6 , [26] and [ABa 2 Cl][Ga 4 S 8 ] (A=Rb, Cs) [27] have been designed and synthesized. However, the large crystal growths of chalcogenides with high optical qualities are much more difficult and inescapably time‐consuming compared to those of most oxides due to the harsh growth conditions.…”