A Potassium Tungsten Oxyfluoride with Strong Second-Harmonic Generation Response Derived from Anion-Ordered Functional Motif

Abstract

The unity of structure-property design and practical synthesis is a key to develop nonlinear optical (NLO) materials. However, many designed structures are hard to get because of the incapability of controlling the arrangement of structural motifs. After careful synthesis, we successfully obtained a new NLO crystal with expected properties, KWO3F, which features a long-range anion-ordered while directed parallel arrangement of [WO5F] d0 transition metal fluorooxo-functional (d0 [TMOF]) motifs. This arrangement is vital to achieve a strong second-harmonic generation (SHG) response, which is proved by dipole moment analyses and theoretical calculations. Remarkably, KWO3F possesses a strong phase-matching SHG response (3 × KDP), high thermal stability (stable up to 350 °C in air), a large laser damage threshold (LDT, 129.7 MW/cm2), a wide transparent window (0.5–10 μm), and a suitable birefringence (0.088 @ 1064 nm). Our research demonstrated that the introduction of the NLO-active d0 [TMOF] motif is an effective strategy to design new potential NLO materials.

Wide bandgaps and strong SHG responses of hetero-oxyfluorides by dual-fluorination-directed bandgap engineering

“…), 6 although, in general, these microstructural building units promote a red-shift in the absorption edge. A structurally related strategy involves fluorination of the TM cation-centered oxyanions 8 in order to blue-shift the absorption edge, but the SHG responses of the resultant materials are usually limited (<1.0 KDP) owing to the often-antiparallel arrangements of the fluorinated TM oxyanions. A complementary approach relies on combination of two types of oxyanions containing SOJT distorted cations; this has been demonstrated by the successful syntheses of a variety of hetero-oxyanion materials with strong SHG responses, 9,10 such as ASe 2 V 3 O 12 (A = Rb, Tl), 9 a A 2 (MoO 3 ) 3 (SeO 3 ) 2 (A = Rb, Tl), 9 b MgTeMoO 6 , 9 c AMoO 3 (IO 3 ) (A = Rb, Cs, NH 4 ) (A = Rb, Cs, NH 4 ), 9 d , e K(VO) 2 O 2 (IO 3 ) 3 , 9 f and [C(NH 2 ) 3 ] 2 Mo 2 O 5 (IO 3 ) 4 ·2H 2 O.…”

Sb5O7I: Exploration of Ternary Antimony-Based Oxyhalide as a Nonlinear-Optical Material

“…Recently, NLO materials containing mixed anions have been considered as promising candidates with optimized comprehensive properties. − Notably, metal oxyhalides, a branch of enormously relevant mixed-anion compounds that have diverse structural features and physical properties, have received rapidly increasing interest. − Metal oxyhalides Bi 7 F 11 O 5 , KWO 3 F, CdPb 2 Te 3 O 8 Cl 2 , Pb 17 O 8 Cl 18 , Pb 13 O 6 Cl 4 Br 10 , and CuSb 2 O 3 X (X = Cl, Br) are reported to exhibit second-harmonic-generation (SHG) responses. It can be noted that most of these oxyhalides are fluorides, chlorides, and bromides, while iodides are very rare because of their synthetic difficulties.…”

[C(NH2)3]2MoO2F4·H2O: Unique Chinese-Knot Structure Revealing Superior Nonlinear-Optical Properties

“…For MO x F y FBBs, there are a wide range of central metal elements to select from the periodic table . The light ones include BeO 3 F tetrahedra in KBBF, and the heavy ones include BiO 4 F 4 polyhedra in Bi­(IO 3 )­F 2 , and in between are several interspersed transition-metal (TM) octahedra and even numerous nonmetal oxyfluorides, such as WO 5 F octahedra in KWO 3 F, PO 3 F tetrahedra in (NH 4 ) 2 PO 3 F, and the IO 2 F 2 seesaw in RbIO 2 F 2 . It is easy to envision that by combining these various MO x F y polyhedra with diverse anionic groups, NLO metal oxyfluorides with excellent performance will be obtained, e.g., NH 4 B 4 O 6 F (3 × KDP), CsSiP 2 O 7 F (0.7 × KDP), K 2 SbP 2 O 7 F (4.0 × KDP), and Ba­(MoO 2 F) 2 (TeO 3 ) 2 (5 × KDP) …”