A₂SnS₅: A Structural Incommensurate Modulation Exhibiting Strong Second‐Harmonic Generation and a High Laser‐Induced Damage Threshold (A=Ba, Sr)

Abstract

Structural modulations have been recently found to cause some unusual physical properties, such as superconductivity or charge density waves; however, thus‐induced nonlinear optical properties are rare. We report herein two unprecedented incommensurately modulated nonlinear optical sulfides exhibiting phase matching behavior, A2SnS5 (A=Ba, Sr), with the (3+1)D superspace groups P21212(00γ)00s or P21(α0γ)0, featuring different modulations of the [Sn2S7]∞ belts. Remarkably, Ba2SnS5 exhibits an excellent second harmonic generation (SHG) of 1.1 times that of the benchmark compound AgGaS2 at 1570 nm and a very large laser‐induced damage threshold (LIDT) of 8×AgGaS2. Theoretical studies revealed that the structural modulations increase the distortions of the Sn/S building units by about 44 or 25 % in A2SnS5 (A=Ba, Sr), respectively, and enhance significantly the SHG compared with α‐Ba2SnSe5 without modulation. Besides, despite the smaller Eg, the A2SnS5 samples exhibit higher LIDTs owing to their smaller thermal expansion anisotropies (Ba2SnS5 (1.51)<Sr2SnS5 (2.08)<AgGaS2 (2.97)).

Sn7Br10S2: The First Ternary Halogen‐Rich Chalcohalide Exhibiting a Chiral Structure and Pronounced Nonlinear Optical Properties

“…[38] Apart from the band gap, several other factors like thermal expansion anisotropy (TEA) also has important influences on the LIDT, [39] which can be evaluated by temperature-dependent lattice parameters. Some NLO compounds possessing smaller TEA could suffer greater thermal shock, [12,28,40] and thus possess higher LIDT values under laser irradiation. As illustrated in Table S8 and Figure S6, the measured TEA of Sn 7 Br 10 S 2 (1.44) is smaller than that of AGS (2.95), [12] and the result suggests that Sn 7 Br 10 S 2 can bear a larger high-power laser irradiation and has an important influence on obtaining a higher LIDT than AGS, which is consistent with the experimental result.…”

Unprecedented mid-infrared nonlinear optical materials achieved by crystal structure engineering, a case study of (KX)P2S6 (X = Sb, Bi, Ba)

“…20 Compared with oxygen, which has intrinsic vibration modes within the infrared spectrum range, suldes constituted from heavier sulfur atoms can have better performance. [21][22][23][24] For sulde MIR NLO materials, they currently remain in a vacuum without a promising material to balance d ij , Dn, and LDT with a bandgap breaking through the "3.5 eV wall". A new research strategy is called for to break the "3.5 eV wall" with a good balance of d ij , Dn, and LDT for MIR NLO.…”

Li4MgGe2S7: The First Alkali and Alkaline‐Earth Diamond‐Like Infrared Nonlinear Optical Material with Exceptional Large Band Gap

“…Nevertheless,t he small band gaps (E g )induced low LDT and two-photon absorption (TPA) in these materials that limit their further applications in high-power lasers.Hence,the exploration of new IR NLO materials with wide band gap and large SHG response is an urgent need but still challenging due to the competition between the wide band gap and large NLO coefficient in one material. [12] Recently,t he non-centrosymmetric diamond-like structure (DLS) was demonstrated as an effective structural template for the design and fabrication of new IR NLO materials.I nD LS,e ach cation must be tetrahedrally coordinated and obey Paulingse lectrostatic valencyr ule,w hich provides af easible design strategy to regulate the properties of materials,like band gap and SHG response,bycombining proper tetrahedral groups,thereby obtaining balanced optical properties in the IR NLO materials. [13] To achieve this point, al arge number of DLS IR NLO materials have been developed, and most of them are mainly composed of univalent alkali metal or IB group metal tetrahedra M I Q 4 (M I = Li, Cu, Ag;Q= S, Se) with IIB,I IIA and IVAg roup element tetrahedra MQ 4 (M = Zn, Cd, Hg, Al, Ga, In, Si, Ge, and Sn).…”