New Nonlinear Optical Materials Research Articles

LnLiSiS4 (Ln = La and Ce): Promising infrared nonlinear optical materials designed by aliovalent substitution from SrCdSiS4

Aliovalent substitution is an effective route to design new nonlinear optical (NLO) crystals. Using SrCdSiS4 as a parent compound, two new infrared NLO lanthanide thiosilicates, namely LnLiSiS4 (Ln = La and Ce), have been successfully obtained through aliovalent substitution. Interestingly, these compounds exhibit [LiSiS4]3- layers composed of vertex- and edge-shared LiS4 and SiS4 tetrahedra that significantly different from the [LnSiS4]3- layers composed of edge-shared LnS6 trigonal prisms (or LnS7 monocapped trigonal prisms) and SiS4 tetrahedra in other ALnSiS4 (A = K, Rb, Cs, Ln = lanthanide) compounds with larger sized alkali cations. LnLiSiS4 (Ln = La and Ce) also achieve balanced properties for good infrared NLO materials: largest SHG response among all known thiosilicates (2.0 and 2.1 × AgGaS2 @ 2 μm for LaLiSiS4 and CeLiSiS4 respectively) with phase matching ability, high laser induced damage threshold (14 and 9 times of AgGaS2), wide bandgap (3.71 and 2.92 eV), wide infrared transmission range (0.35–18 μm) and good thermal stability above 700 °C. This work not only enriches the structure chemistry of lanthanide thiosilicates, but also provides an efficient route to design new high performance IR NLO materials.

Sr3[SnOSe3][CO3]: A Heteroanionic Nonlinear Optical Material Containing Planar π‐conjugated [CO3] and Heteroleptic [SnOSe3] Anionic Groups

AbstractInorganic heteroanionic materials are attracting increasing attention for exploring new nonlinear optical (NLO) materials because they could better satisfy the necessary but conflicting properties of NLO crystals, e.g. large SHG response and wide band‐gap. Up to now, the reports on heteroanionic NLO materials have mainly focused on ultraviolet or visible oxide‐based fluoroborates, fluorophosphates, borate‐phosphates and borate‐iodates. However, chalcogenides containing different kinds of anionic groups have barely been reported. Herein, we have synthesized the first oxychalcogenide‐carbonate, Sr3[SnOSe3][CO3] that contains two different kinds of anionic groups, [SnOSe3] and [CO3]. It crystallizes in a noncentrosymmetric space group and exhibits fascinating NLO properties, including a large SHG response (≈1×AGS), sufficient birefringence (0.12 @1064 nm), wide band‐gap (3.46 eV) and high laser damage threshold (240 MW cm−2). These make Sr3[SnOSe3][CO3] a promising NLO crystal.

Sr3[SnOSe3][CO3]: A Heteroanionic Nonlinear Optical Material Containing Planar π‐conjugated [CO3] and Heteroleptic [SnOSe3] Anionic Groups

AbstractInorganic heteroanionic materials are attracting increasing attention for exploring new nonlinear optical (NLO) materials because they could better satisfy the necessary but conflicting properties of NLO crystals, e.g. large SHG response and wide band‐gap. Up to now, the reports on heteroanionic NLO materials have mainly focused on ultraviolet or visible oxide‐based fluoroborates, fluorophosphates, borate‐phosphates and borate‐iodates. However, chalcogenides containing different kinds of anionic groups have barely been reported. Herein, we have synthesized the first oxychalcogenide‐carbonate, Sr3[SnOSe3][CO3] that contains two different kinds of anionic groups, [SnOSe3] and [CO3]. It crystallizes in a noncentrosymmetric space group and exhibits fascinating NLO properties, including a large SHG response (≈1×AGS), sufficient birefringence (0.12 @1064 nm), wide band‐gap (3.46 eV) and high laser damage threshold (240 MW cm−2). These make Sr3[SnOSe3][CO3] a promising NLO crystal.

Band gap modulation and nonlinear optical properties of quaternary tellurates Li2GeTeO6.

Tellurate crystals are attractive for developing new nonlinear optical (NLO) materials in the mid-infrared region due to their wide transmission window. In this work, we report a quaternary tellurate oxide crystal, Li2GeTeO6, which exhibits a short cutoff edge (240 nm) with a powder second harmonic generation (SHG) response of 1.3 × KH2PO4 (KDP). The reported material reveals the largest band gap in the Li2MTeO6 (M = tetravalent cation) family. The first-principles calculations were used to illustrate the origin of the NLO effect. These results highlight the band gap engineering based on the cation substitution strategy for designing new NLO materials with balanced optical properties.

Rational combination of multiple structural groups on regulating nonlinear optical property in hexagonal Ln3MGeS7 polar crystals

Combination of multiple structural groups was developed as one effective method for regulating material property and exploring new nonlinear optical (NLO) crystals. For that reason, four Ln3MGeS7 (Y3LiGeS7, Y3Cd0.5GeS7, Gd3Cd0.5GeS7 and Sm3Zn0.5GeS7) crystals with various structural motifs were successfully synthesized and systematically investigated. Note that Y3LiGeS7 and Y3Cd0.5GeS7 were firstly synthesized so far. Performance test shows that Ln3MGeS7 compounds exhibit the variable optical bandgaps (1.62–2.33 eV) and good second harmonic generation (SHG) responses (0.7–1.1 × commercial AgGaS2) with requisite phase-matching behavior, which agree well with the theoretical results (Y3LiGeS7: Δn = 0.058 and d33 = 19.97 pm/V; Y3Cd0.5GeS7: Δn = 0.055 and d33 = 20.6 pm/V) and introduction of MIIB (Zn, Cd) atoms into crystal structure is conducive to enlarge the SHG effect. SHG density and dipole-moment calculations indicate that their SHG effects are originated from the major contribution on LnSn units with moderate effect of GeS4 and MIIBS6 (Zn, Cd) ligands. Therefore, selecting appropriate functional motifs (LnSn and MIIB) into crystal structure can promote the enhancement of NLO property and further realize the rational design of new promising infrared NLO materials.

Tin Metal Cluster Compounds as New Third-Order Nonlinear Optical Materials by Computational Study.

It is quite appealing but challenging to predict and synthesize new nonlinear optical (NLO) materials with exceptional performance. Herein, the different Sn4 cluster core structures and third-order NLO properties are studied through electronic structure, excited hole-electron, bonding character, and aromaticity analysis. As a result, Sn4 clusters with ring core structure (Sn4-R) not only have the smallest Egap, the largest UV-vis response intensity, but also the strongest third-order NLO response in our work. As proved by natural bond orbitals' (NBO) analysis, electron localization function (ELF), and adaptive natural density partitioning (AdNDP), the Sn44+ has two in-plane four center-two electron (4c-2e) Sn-Sn σ-bonds, resulting in a good delocalization. For the first time, delocalization of metal cluster cores in tin clusters that is beneficial to the third-order NLO response is proposed, which provides a new guidance to design and prepare third-order NLO materials.

Unique Unilateral-Chelated Mode-Induced d–p−π Interaction Enhances Second-Harmonic Generation Response in New Ln3LiMS7 Family

Multiple chelated configurations of anionic groups offer a great chance to design new nonlinear optical (NLO) materials with excellent performances for infrared (IR) application. In this work, the new polar Ln3LiMS7 (Ln = rare-earth; M = Ge, Sn) family as promising IR NLO candidates were successfully designed and synthesized by the unique close-ring combination between LnS8 and MS4 ligands. Note that La3LiGeS7 and La3LiSnS7 exhibit the good NLO effects (0.7 vs 1.2 × benchmark AgGaS2) with phase-matching behavior and high laser damage thresholds (6.0 vs 2.5 × AgGaS2), respectively. First-principles calculation indicates that their NLO effects originate from the synergistic effect of intrinsic dipole moments and d–p delocalized-π electron-induced dipole oscillations in the Ln3LiMS7 family. This result also verifies that unique unilateral-chelated configuration induced d–p−π interactions are beneficial to improve the NLO performances, which offers us one feasible way (incorporation of Ln-centered ligands into crystal structure) to design new promising IR NLO materials.

M(NH2 SO3 )2 (M=Sr, Ba): Two Deep-Ultraviolet Transparent Sulfamates Exhibiting Strong Second Harmonic Generation Responses and Moderate Birefringence.

Over the last few decades, the development of each new nonlinear optical (NLO)-active functional unit has led to the discoveries of a series of excellent NLO materials. In the present work, based on first-principles studies, we identified a novel deep-UV (DUV) NLO-active functional unit, a non-π-conjugated group viz. (NH2 SO3 )- . By combining alkaline-earth metals with (NH2 SO3 )- group, two DUV transparent NLO sulfamates, M(NH2 SO3 )2 (M=Sr, Ba) with superior optical properties including strong SHG responses (1.2 and 2.7 × KH2 PO4 (KDP)), short UV cut-off edge (<190 nm) and moderate birefringence (0.056@589.3 nm for Sr(NH2 SO3 )2 ) were successfully synthesized. Our work has provided not only two promising DUV transparent NLO crystals, but also an innovative non-π-conjugated unit for developing more DUV transparent NLO materials.

M(NH2SO3)2 (M=Sr, Ba): Two Deep‐Ultraviolet Transparent Sulfamates Exhibiting Strong Second Harmonic Generation Responses and Moderate Birefringence

AbstractOver the last few decades, the development of each new nonlinear optical (NLO)‐active functional unit has led to the discoveries of a series of excellent NLO materials. In the present work, based on first‐principles studies, we identified a novel deep‐UV (DUV) NLO‐active functional unit, a non‐π‐conjugated group viz. (NH2SO3)−. By combining alkaline‐earth metals with (NH2SO3)− group, two DUV transparent NLO sulfamates, M(NH2SO3)2 (M=Sr, Ba) with superior optical properties including strong SHG responses (1.2 and 2.7 × KH2PO4 (KDP)), short UV cut‐off edge (&lt;190 nm) and moderate birefringence (0.056@589.3 nm for Sr(NH2SO3)2) were successfully synthesized. Our work has provided not only two promising DUV transparent NLO crystals, but also an innovative non‐π‐conjugated unit for developing more DUV transparent NLO materials.

AMnAs3S6 (A = Cs, Rb): Phase-Matchable Infrared Nonlinear Optical Functional Motif [As3S6]3- Obtained via Surfactant-Thermal Method.

Exploration of a new nonlinear optical (NLO)-active functional motif is important in the rational design of promising infrared (IR) NLO materials. Compared with typical tetrahedral MQ4 (M = IIB, III, IV metals; Q = S, Se) motifs, MQ3 (M = As, Sb) pyramids favor high second-harmonic generation (SHG) efficiency while frequently hindering phase matching (PM) because of excessively large optical anisotropy. The surfactant-thermal method was first adopted to achieve PM in MQ3-containing systems and synthesize mixed covalent-ionic IR NLO materials. Two new thioarsenates of AMnAs3S6 (A = Cs, Rb) exhibiting strong PM SHG efficiencies comparable to commercial AGS and laser-induced damage thresholds of one order higher than AGS were obtained. The [As3S6]3- unit in their structures is an unprecedented NLO-active functional motif, which can be useful in designing new IR NLO compounds with large SHG efficiency. In addition, the surfactant-thermal method provides a new general strategy for synthesizing new IR NLO materials.

Zn3B7O13Cl: A New Deep-Ultraviolet Transparency Nonlinear Optical Crystal with Boracite Structure

Nonlinear optical crystals play important roles in modern laser science and technology. However, the design and growth of new nonlinear optical (NLO) materials is still a challenging issue for researchers. Due to the excellent performance of Mg3B7O13Cl crystal, we paid attention to the optimization of its structure, in order to find new NLO materials with favorable properties. Here, Zn3B7O13Cl crystals were obtained by a high-temperature solution method. Its structure was determined to be the trigonal symmetry with a polar space group of R3c, which is more highly symmetric than that of Mg3B7O13Cl (Pca21). The experimental and theoretical investigations demonstrated that the title compound exhibits a short absorption cutoff (band gap ∼6.53 eV), moderate SHG responses (2.2 times that of KDP at 1064 nm), and the improved birefringence, which results from the large distortion and anisotropy of borate groups and zinc polyhedrons. Therefore, the structural modification of Mg3B7O13Cl by zinc cations achieves a balance between the deep-ultraviolet transparency, the nonlinear optical effect, and the moderate birefringence, which is very significant for the design of practical NLO materials.

Sr6Cd2Sb6O7S10: Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups

AbstractA new nonlinear optical (NLO) oxysulfide, Sr6Cd2Sb6O7S10, which contains the functional groups [SbOxS5−x]7− (x=0, 1) with a 5s2 electron configuration, is synthesized by a solid‐state reaction. This compound displays a phase‐matchable second harmonic generation (SHG) response four times stronger than AgGaS2 (AGS) under laser irradiation at 2.09 μm. Single‐crystal‐based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS4]7− and [SbS5]7− pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS4]7− units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns2 electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.

Sr6 Cd2 Sb6 O7 S10 : Strong SHG Response Activated by Highly Polarizable Sb/O/S Groups.

A new nonlinear optical (NLO) oxysulfide, Sr6 Cd2 Sb6 O7 S10 , which contains the functional groups [SbOx S5-x ]7- (x=0, 1) with a 5s2 electron configuration, is synthesized by a solid-state reaction. This compound displays a phase-matchable second harmonic generation (SHG) response four times stronger than AgGaS2 (AGS) under laser irradiation at 2.09 μm. Single-crystal-based optical measurements reveal a SHG intensity that can be tuned by temperature and novel photoluminescence properties. Theoretical analyses demonstrate that tetragonal [SbOS4 ]7- and [SbS5 ]7- pyramids make the predominant contribution to the enhanced SHG effect. Among those, the [SbOS4 ]7- units with mixed anions make a larger contribution. This work proposes that oxysulfide groups with an ns2 electron configuration can serve as new functional building units in NLO materials and opens a new avenue for the design of other optoelectronic materials.

A review on the development of infrared nonlinear optical materials with triangular anionic groups

Exploration of new nonlinear optical (NLO) materials in the infrared (IR) region is of importance in many civil and military fields. Fundamental building units (FBUs) play the critical roles in the origin of NLO effect for chalcogenide system, such as tetrahedral and triangular anionic groups. Note that some triangular groups can generate the relatively strong NLO effect owing to their distinctive π-conjugated electron orbitals or other unique structures. This review focuses on the metal sulfides with triangular anionic groups and has systematically studied the relationship between structure and performances. Compared to the known materials, the common choice for different MS3 (M = B, Sb, As, Ag, Cu, Te, Sn) units are introduced in detail. This review also summarizes the mechanism of MS3 to provide useful insights into the development of NLO materials with better performances.

NH4 Be2 BO3 F2 and γ-Be2 BO3 F: Overcoming the Layering Habit in KBe2 BO3 F2 for the Next-Generation Deep-Ultraviolet Nonlinear Optical Materials.

KBe2 BO3 F2 (KBBF) is still the only practically usable crystal that can generate deep-ultraviolet (DUV) coherent light by direct second harmonic generation (SHG). However, applications are hindered by layering, leading to difficulty in the growth of thick crystals and compromised mechanical integrity. Despite efforts, it is still a great challenge to discover new nonlinear optical (NLO) materials that overcome the layering while keeping the DUV SHG available. Now, two new DUV NLO beryllium borates have been successfully designed and synthesized, NH4 Be2 BO3 F2 (ABBF) and γ-Be2 BO3 F (γ-BBF), which not only overcome the layering but also can be used as next-generation DUV NLO materials with the shortest type I phase-matching second-harmonic wavelength down to 173.9 nm and 146 nm, respectively. Significantly, γ-BBF is superior to KBBF in all metrics and would be the most outstanding DUV NLO crystal.

CsB4 O6 F: A Congruent-Melting Deep-Ultraviolet Nonlinear Optical Material by Combining Superior Functional Units.

The discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep-ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB4 O6 F (CBF), which combines the superior structural properties of two well-known NLO materials, β-BaB2 O4 (BBO) and KBe2 BO3 F2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (≈1.9×KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials.

CsB4O6F: A Congruent‐Melting Deep‐Ultraviolet Nonlinear Optical Material by Combining Superior Functional Units

AbstractThe discovery of new nonlinear optical (NLO) materials for coherent light generation in the deep‐ultraviolet (DUV, wavelength below 200 nm) region is essential for the development of laser technologies. Herein, we report a new material CsB4O6F (CBF), which combines the superior structural properties of two well‐known NLO materials, β‐BaB2O4 (BBO) and KBe2BO3F2 (KBBF). CBF exhibits excellent DUV optical properties including a short cutoff edge (155 nm), a large SHG response (≈1.9×KDP), and a suitable birefringence that enables frequency doubling down to 171.6 nm. Remarkably, CBF melts congruently and shows an improved growth habit. In addition, our rational design strategy will contribute to the discovery of DUV NLO materials.

"All-Three-in-One": A New Bismuth-Tellurium-Borate Bi3TeBO9 Exhibiting Strong Second Harmonic Generation Response.

A new nonlinear optical (NLO) material, Bi3TeBO9 (BTBO), is successfully grown from high temperature solution method. BTBO crystallizes in a polar space group of P63 with a framework structure composed of [Bi3O9] blocks, with TeO6 and BO3 interconnection. It is interesting that in the BTBO structure three types of NLO-active units, including stereochemically active lone pair cations (Bi3+ cations), second-order Jahn-Teller distorted octahedra (TeO6 octahedra) and π-orbital planar groups (BO3 groups), simultaneously exist. The additive contribution from these three types of groups results in an extremely large second harmonic generation (SHG) response in BTBO (about 20 times that of KDP), exhibiting the largest SHG effect among the known borate NLO materials. The enhancement of the nonlinear optical property is elucidated by the first-principles analysis.

Crystal structures and non-linear optics of several types of bimetallic assemblies comprising chiral Cu(II) complexes

Analogous to the non-linear optical properties of L-alaninium perrhenate ionic crystals with three-dimensional hydrogen bonds, we have synthesized various chiral bimetallic assemblies, [CuL2][Ni(CN)4]·2H2O (Cu(II)–Ni(II)), [CuL2]3[Co(CN)6]2·5H2O·4DMSO (Cu(II)–Co(III)), [CuL2]2[Fe(CN)6]·10H2O (Cu(II)–Fe(II)), [CuL2]2[CrO4]2·5H2O (Cu(II)–Cr(VI)) and [CuL2]2[MoO4]2·3H2O·2DMSO (Cu(II)–Mo(VI)) (L=(1R,2R)-diphenylethylenediamine), determined their crystal structures at different temperatures; measured their spectroscopic and magnetic properties and confirmed their non-linear optical properties. One-dimensional Cu(II)–Ni(II) crystallizes in the P1 space group and exhibits no NLO properties. However, two-dimensional Cu(II)–Co(III) crystallizes in the P21 space group and three-dimensional Cu(II)–Fe(II) crystallizes in the C2 space group; both exhibit NLO properties. Moreover, the complexes Cu(II)–Cr(VI) and Cu(II)–Mo(VI) crystallize in polar crystals of P21 symmetry involving two-dimensional hydrogen bonding and exhibit NLO properties. These Cu(II)–Cr(VI) and Cu(II)–Mo(VI) crystals are so flexible that they exhibit anisotropic thermal negative expansion. Therefore, their second-harmonic generation efficiency makes them potentially useful as new materials for non-linear optics.

Salts of guanidine derivatives - new materials for non-linear optics

Salts of guanidine derivatives - new materials for non-linear optics