RbIO₃ and RbIO₂F₂: Two Promising Nonlinear Optical Materials in Mid-IR Region and Influence of Partially Replacing Oxygen with Fluorine for Improving Laser Damage Threshold

Abstract

Laser damage threshold (LDT) has been considered as a key index, apart from the nonlinear optical (NLO) effect, to characterize the performance of a mid-infrared NLO material. This paper reports and compares the properties of RbIO3 and RbIO2F2 as potential nonlinear optical (NLO) materials to be used in the mid-IR region. RbIO3 is a known compound, and its powder SHG (second harmonic generation) effect is carefully measured in this work for the first time to be as strong as 20 times that of KDP, and its powders show a high damage threshold (LDT) of 125 MW/cm2. In order to investigate the influence on the properties by partially replacing oxygen with fluorine atoms, the new compound RbIO2F2 is synthesized and characterized. Although it also shows relatively strong powder SHG responses 4 times that of KDP, the LDT value of the powders is improved to 156 MW/cm2. The transparent region and the thermal stability of two compounds are also measured with satisfactory results. The electronic structure and the properties of the materials are also investigated by the theoretical approach. All these indicate that RbIO3 and RbIO2F2 are both promising candidates for NLO materials to be used in the mid-IR region and that partially replacing oxygen with fluorine in the molecule can improve the laser damage threshold of the material.

(NH4)Bi2(IO3)2F5: An Unusual Ammonium‐Containing Metal Iodate Fluoride Showing Strong Second Harmonic Generation Response and Thermochromic Behavior

“…As a result, a series of excellent iodate SHG crystals have been reported, including AMoO 3 (IO 3 ) (A=Rb, Cs), BaNbO(IO 3 ) 5 , NaI 3 O 8 , A 2 Ti(IO 3 ) 6 (A=Li, Na), (NH 4 )[MoO 3 (IO 3 )], ReI 5 O 14 (Re=Y and Gd), BiO(IO 3 ), and Bi 2 (IO 4 )(IO 3 ) 3 . Recently, fluorine‐containing iodates, such as Bi(IO 3 )F 2 , Bi 3 OF 3 (IO 3 ) 4 , ABi 2 (IO 3 ) 2 F 5 (A=K, Rb, Cs), α‐ and β‐Ba[VFO 2 (IO 3 ) 2 ], α‐ and β‐Ba 2 [VO 2 F 2 (IO 3 ) 2 ]IO 3 , α‐ and β‐Ba 2 [GaF 4 (IO 3 ) 2 ](IO 3 ), RbIO 2 F 2 , CsIO 2 F 2 , and Ce(IO 3 ) 2 F 2 ⋅H 2 O, have been demonstrated to be new types of promising NLO iodate crystals. The introduction of fluoride into iodates can not only enrich the crystal structure but can also broaden the band gap and enlarge the laser damage threshold (LDT) .…”

“…Recently, fluorine‐containing iodates, such as Bi(IO 3 )F 2 , Bi 3 OF 3 (IO 3 ) 4 , ABi 2 (IO 3 ) 2 F 5 (A=K, Rb, Cs), α‐ and β‐Ba[VFO 2 (IO 3 ) 2 ], α‐ and β‐Ba 2 [VO 2 F 2 (IO 3 ) 2 ]IO 3 , α‐ and β‐Ba 2 [GaF 4 (IO 3 ) 2 ](IO 3 ), RbIO 2 F 2 , CsIO 2 F 2 , and Ce(IO 3 ) 2 F 2 ⋅H 2 O, have been demonstrated to be new types of promising NLO iodate crystals. The introduction of fluoride into iodates can not only enrich the crystal structure but can also broaden the band gap and enlarge the laser damage threshold (LDT) . Notably, the bismuth‐containing iodates mentioned above usually possess large SHG responses because of the potentiation of polarizable lone‐pair electrons in Bi 3+ .…”

Growth, Properties, and Theoretical Analysis of M2LiVO4 (M = Rb, Cs) Crystals: Two Potential Mid-Infrared Nonlinear Optical Materials

“…In recent research, many studies pay special attention to halides, iodates, molybdates, and vanadates since they normally exhibit large E g and diverse structural motifs so that it is possible to find materials with a subtle balance between large NLO efficiency and high LDT. A series of potential Mid-IR NLO crystals have been achieved, such as Pb 17 O 8 Cl 18 19 , α -AgI 3 O 8 and β -AgI 3 O 8 20 , RbIO 3 21 , Na 2 Te 3 Mo 3 O 16 22 , BaTeMo 2 O 9 23 , LiNa 5 Mo 9 O 30 24 , K 3 V 5 O 14 25, 26 and YCa 9 (VO 4 ) 7 27 . After a lot of screening and system performance evaluation, we think that Rb 2 LiVO 4 (RLVO) and Cs 2 LiVO 4 (CLVO) are good Mid-IR NLO materials.…”

Bi(IO3)F2: The First Metal Iodate Fluoride with a Very Strong Second Harmonic Generation Effect

“…[3][4][5][6][7][8][9][10] These research efforts afforded alarge number of metal iodates with excellent SHG properties,i ncluding BaNbO(IO 3 ) 5 , [6a] BiOIO 3 , [8a] and AgI 3 O 8 . [11] Owing to the presence of IÀFb onds, iodates of this class are more suitably named metal fluoroiodates.AsI À Obonds are much stronger than I À Fbonds,metal fluoroiodates are obtained at high F/I molar ratios.A mong the structurally characterized fluoroiodates,a ll of them display very simple structures with isolated [IO 2 F 2 ] À or [IOF 4 ] À anions,a nd only the isostructural compounds RbIO 2 F 2 and KIO 2 F 2 crystallize in an acentric space group. [11] Owing to the presence of IÀFb onds, iodates of this class are more suitably named metal fluoroiodates.AsI À Obonds are much stronger than I À Fbonds,metal fluoroiodates are obtained at high F/I molar ratios.A mong the structurally characterized fluoroiodates,a ll of them display very simple structures with isolated [IO 2 F 2 ] À or [IOF 4 ] À anions,a nd only the isostructural compounds RbIO 2 F 2 and KIO 2 F 2 crystallize in an acentric space group.…”

“…[10a] Recently,afluorine-containing NLO-active metal iodate, namely RbIO 2 F 2 ,w as synthesized by reacting RbIO 3 and concentrated hydrofluoric acid solution at 230 8 8C( high F/I molar ratio of 23:1). [11] Owing to the presence of IÀFb onds, iodates of this class are more suitably named metal fluoroiodates.AsI À Obonds are much stronger than I À Fbonds,metal fluoroiodates are obtained at high F/I molar ratios.A mong the structurally characterized fluoroiodates,a ll of them display very simple structures with isolated [IO 2 F 2 ] À or [IOF 4 ] À anions,a nd only the isostructural compounds RbIO 2 F 2 and KIO 2 F 2 crystallize in an acentric space group. [12] Thes eesaw-shaped [IO 2 F 2 ] À moiety has as maller dipole moment than the IO 3 À group,a nd hence the SHG effect of RbIO 2 F 2 (4 times larger than that of KH 2 PO 4 (KDP)) is much weaker than that of RbIO 3 (20 times larger than that of KDP).…”