Large Second Harmonic Generation Response Research Articles

Na4Yb(CO3)3F: A New UV Nonlinear Optical Material with a Large Second Harmonic Generation Response

A new nonlinear optical crystals fluoride carbonate, Na4Yb(CO3)3F, has been synthesized by mild hydrothermal method. The Na4Yb(CO3)3F crystallizes in the noncentrosymmetric space group Cc (no. 9) with the lattice parameters a = 8.018(3), b = 15.929(5), c = 13.950(5) Å and β = 101.425(6)°. The compound Na4Yb(CO3)3F has a high density of [CO3] groups. The structure can be described as one-dimensional [Na5Yb(CO3)2F2] chains connected by [CO3] groups, forming an intricate three-dimensional (3D) framework. Other Na+ and Yb3+ cations are located in the cavities of 3D network. The powder second harmonic generation (SHG) measurement shows that Na4Yb(CO3)3F features a large SHG response, about 4.3 times that of KH2PO4 (KDP), and is a phase-matchable material. In addition, its UV-Vis-NIR diffuse reflectance spectral data indicate that Na4Yb(CO3)3F has a large optical gap about 4.72 eV, which corresponds to the UV cut-off edge of 263 nm.

Advantageous Units in Antimony Sulfides: Exploration and Design of Infrared Nonlinear Optical Materials.

The exploration of infrared (IR) nonlinear optical (NLO) materials remains attractive because of the urgent requirements in the laser field. Meanwhile, the deepened cognition of structure-property relationships is necessary to help guide the exploration of IR NLO materials. So far, the family of antimony sulfides is an important system with a lot of attention, and a series of antimony sulfides are reported. However, it is urgent to reveal how different Sb-S units, like SbS3, SbS4, and more complex combinations, affect apparent properties. Here, taking ternary metal antimony sulfides as examples, the sources of some essential optical properties, such as second harmonic generation (SHG) and birefringence, are systematically analyzed through first-principles calculations, and the mechanisms of the performances with various magnitudes are also presented to clarify the structure-property relationships. The results indicate that the SbS4 unit among antimony sulfides is an advantageous NLO-active unit, which can balance the contradiction between the band gap and SHG response. Introduction of transition metals in the Sb-S anionic frameworks can tune the magnitude of birefringence. Besides, the substitution of a cation from a transition metal to an alkali metal can notably enlarge the band gap and maintain a large SHG response. These design strategies are beneficial to explore potential IR NLO materials with Sb-S units.

Rb3VO(O2)2CO3: A Four‐in‐One Carbonatoperoxovanadate Exhibiting an Extremely Strong Second‐Harmonic Generation Response

AbstractA nonlinear optical (NLO) carbonatoperoxovanadate, Rb3VO(O2)2CO3, was synthesized through a simple solution‐evaporation method in phase‐pure form. Single‐crystal X‐ray diffraction revealed that the structure of Rb3VO(O2)2CO3 consists of important noncentrosymmetric (NCS) chromophores, that is, π‐delocalized (CO3)2− groups, a second‐order Jahn–Teller (SOJT) distortive V5+ cation, and π‐localized distorted O22− groups, as well as charge‐balancing polarizable Rb+ ions. The powder second‐harmonic generation (SHG) measurements indicated that Rb3VO(O2)2CO3 is phase‐matchable (Type I) and exhibits a remarkably strong SHG response circa 21.0 times that of potassium dihydrogen phosphate (KDP), which is the largest efficiency observed among carbonate NLO materials. First‐principles calculation analysis suggests that the extremely large SHG response of Rb3VO(O2)2CO3 is attributed to the synergistic effect of the cooperation of all the constituting NCS chromophores.

Rb3 VO(O2 )2 CO3 : A Four-in-One Carbonatoperoxovanadate Exhibiting an Extremely Strong Second-Harmonic Generation Response.

A nonlinear optical (NLO) carbonatoperoxovanadate, Rb3 VO(O2 )2 CO3 , was synthesized through a simple solution-evaporation method in phase-pure form. Single-crystal X-ray diffraction revealed that the structure of Rb3 VO(O2 )2 CO3 consists of important noncentrosymmetric (NCS) chromophores, that is, π-delocalized (CO3 )2- groups, a second-order Jahn-Teller (SOJT) distortive V5+ cation, and π-localized distorted O22- groups, as well as charge-balancing polarizable Rb+ ions. The powder second-harmonic generation (SHG) measurements indicated that Rb3 VO(O2 )2 CO3 is phase-matchable (Type I) and exhibits a remarkably strong SHG response circa 21.0 times that of potassium dihydrogen phosphate (KDP), which is the largest efficiency observed among carbonate NLO materials. First-principles calculation analysis suggests that the extremely large SHG response of Rb3 VO(O2 )2 CO3 is attributed to the synergistic effect of the cooperation of all the constituting NCS chromophores.

Cs3VO(O2)2CO3: an exceptionally thermostable carbonatoperoxovanadate with an extremely large second-harmonic generation response.

A novel nonlinear optical (NLO) carbonatoperoxovanadate, Cs3VO(O2)2CO3, with an exceptionally high thermostability was successfully synthesized by introducing highly polarizable Cs+ cations and inorganic polydentate carbonate anions into asymmetric peroxovanadates. The structure of Cs3VO(O2)2CO3 is composed of distorted [VO(O2)2CO3]3- units and charge balancing Cs+ cations. The title compound exhibits the largest NLO intensity ever found in the current carbonate NLO materials, i.e., 23.0 times that of KH2PO4 (KDP). The remarkably strong second-harmonic generation (SHG) response originates from the synergistic effect of the exceedingly polarizable Cs+ cations, distortive polyhedra of the V5+ cation, delocalized π orbitals in CO3 groups, and distorted localized π orbitals in O2 groups. First-principles calculations indicated that introducing the polarizable cations into peroxovanadates not only induces the enhancement of the SHG response but also improves the thermal stability of the framework.

Na2ZnSn2S6: A mixed-metal thiostannate with large second-harmonic generation response activated by penta-tetrahedral [ZnSn4S14]10− clusters

A sodium zinc thiostannate Na2ZnSn2S6 is reported with its interesting structural features and property characteristics. It crystallizes in the polar space group Fdd 2 (No. 43) with the unit cell parameters of a =12.945(3) A, b =23.556(5) A, c =7.2774(15) A and Z =8. In its structure, Zn-centered penta-tetrahedra [ZnSn4S15]12− clusters arrange regularly along the diagonals of ab and ac planes to form a 3D tunnel structure with charge-balanced Na+ cations located inside the tunnels. Note that SnS4 tetrahedra connect with each other by sharing corners to form infinite ∞ [SnS3] n chains that are rarely found in known alkali-thiostannates. Remarkably, Na2ZnSn2S6 exhibits the good NLO performances, such as large SHG response (4 times that of AgGaS2 at 55–88 μm under the 2.09 μm radiation), wide infrared (IR) transmission region (0.35–25 μm) and relatively high laser damage threshold (77.5 MW/cm2, ~2 times that of AgGaS2). Theoretical calculations have also been performed to investigate the structure-property relationship and the results indicate that the origin of NLO effect can be attributed to the penta-tetrahedra [ZnSn4S15]12− clusters.

Na2CdGe2Q6 (Q = S, Se): two metal-mixed chalcogenides with phase-matching abilities and large second-harmonic generation responses.

In view of their inherent defects for commercial infrared nonlinear optical (IR NLO) materials, exploration for new IR NLO materials with excellent performance is an imperative and meaningful work. Herein, we report the successful design and synthesis of two metal-mixed chalcogenides containing divalent cations with d10 electronic configuration: Na2CdGe2S6 and Na2CdGe2Se6. Both of them crystallize in the polar Cc space group and exhibit three-dimensional tunnel structures constructed by the CdQ4 tetrahedra and ∞[GeQ3]n chains with Na+ located in the tunnels. Furthermore, an interesting space group transformation between the monoclinic (Cc) and tetragonal (I4/mcm) systems from Na2CdGe2Se6 to Na2ZnGe2Se6 was discovered, which may arise from the different connection types of their building blocks (more flexible corner-sharing type in Cc while tightly edge-sharing type in I4/mcm). Remarkably, they exhibit type-I phase-matching abilities and large second harmonic generation (SHG) responses (0.8 and 2 times that of benchmark AgGaS2 at 2.09 μm fundamental light). Notably, Na2CdGe2S6 satisfies the essential requirements (coexistence of large NLO response and high laser damage threshold) as one excellent IR NLO material. The structure-property relationship has also been investigated through theoretical calculations and the results indicate that the origin of their NLO effects can be attributed to CdQ4 and GeQ4 units.

A new cerium iodate infrared nonlinear optical material with a large second-harmonic generation response

A new rare earth ternary iodate, Ce2I6O18, has been synthesized by a high temperature hydrothermal method with homemade alloy reactor equipment.

Experimental and ab initio studies of Cd5(BO3)3Cl: the first cadmium borate chlorine NLO material with isolated BO3 groups.

A nonlinear optical crystal cadmium borate chlorine (Cd5(BO3)3Cl) has been successfully grown through a spontaneous crystallization method. Cd5(BO3)3Cl crystallizes in the noncentrosymmetric space group Cm with isolated BO3 and distorted CdOnClm (n = 4, 5, 7; m = 0, 1, 2) polyhedra. Powder second harmonic generation (SHG) measurements on polycrystalline Cd5(BO3)3Cl indicated that the title compound is phase-matchable in the visible region and exhibits a large SHG response of about 5 × KH2PO4 (KDP). Further optical characterization suggested that the compound has a wide transparent region ranging from UV to near IR with a UV cutoff edge at about 295 nm. In addition, first-principles electronic structure calculations revealed that the macroscopic SHG coefficients of Cd5(BO3)3Cl originate from the cooperative effects of the BO3 groups with asymmetric π-delocalization, the d10 cation Cd2+ with the polar displacement and the Cl- anions.

AZn2BO3X2(A = K, Rb, NH4; X = Cl, Br): New Members of KBBF Family Exhibiting Large SHG Response and the Enhancement of Layer Interaction by Modified Structures

A new category of five KBBF-analogy nonlinear optical (NLO) materials, AZn2BO3X2 (A = K, Rb, NH4; X = Cl, Br), are developed by the tetrahedron substitution of BeO3F for ZnO3X from KBe2BO3F2 (KBBF). They preserve the structural merits of KBBF, consisting of the infinite planar [Zn2BO3X2]∞ layers. Optical measurements on this series of NLO crystals reveal that they are phase-matchable in the visible and UV region with powder second-harmonic generation (SHG) responses being more than twice that of isostructural KBBF. First-principles calculations and atom-cutting analysis were carried out to demonstrate that enhanced SHG response originates from the cooperative effect of coparallel [BO3] triangles and distorted ZnO3Cl/Br tetrahedra. The theoretical calculations and experimental results show that AZn2BO3X2 exhibits a less-developed layer habit compared with KBBF. Especially, because of the existence of relatively strong hydrogen bond between NH4+ groups and [Zn2BO3Cl2]∞ layers, NH4Zn2BO3Cl2 crystal exhibits ...

A New Deep-Ultraviolet Transparent Orthophosphate LiCs2PO4 with Large Second Harmonic Generation Response.

LiCs2PO4, a new deep-ultraviolet (UV) transparent material, was synthesized by the flux method. The material contains unusual edge-sharing LiO4-PO4 tetrahedra. It exhibits a very short absorption edge of λ = 174 nm and generates the largest powder second harmonic generation (SHG) response for deep-UV phosphates that do not contain additional anionic groups, i.e., 2.6 times that of KH2PO4 (KDP). First-principles electronic structure analyses confirm the experimental results and suggest that the strong SHG response may originate from the aligned nonbonding O-2p orbitals. The discovery and characterization of LiCs2PO4 provide a new insight into the structure-property relationships of phosphate-based nonlinear optical materials with large SHG responses and short absorption edges.

Na2ZnGe2S6: A New Infrared Nonlinear Optical Material with Good Balance between Large Second-Harmonic Generation Response and High Laser Damage Threshold.

The development of frequency-conversion technology in the infrared region is in urgent need of new excellent infrared nonlinear optical (IR NLO) materials. How to achieve a good balance between laser damage threshold (LDT) and NLO coefficient (dij) for new IR NLO candidates is still a challenge. The combination of the highly electropositive alkali metal (Na) and Zn with d(10) electronic configuration into crystal structure affords one new IR NLO material, Na2ZnGe2S6. It exhibits excellent properties including a wide transparent region (0.38-22 μm), large band gap (3.25 eV), and especially a balance between a strong NLO coefficient (30-fold that of KDP) and a high LDT (6-fold that of AgGaS2), indicating a promising application in the IR region. Moreover, novel common-vertex-linked wavelike ∞[GeS3]n chains are interestingly discovered in Na2ZnGe2S6, which rarely exist in the reported thiogermanides containing alkali metals. In addition, calculated SHG density and dipole moment demonstrate that the large NLO response is mainly attributed to the cooperative effects of the [GeS4] and [ZnS4] units.

Electronic, Crystal Chemistry, and Nonlinear Optical Property Relationships in the Dugganite A3B3CD2O14 Family.

A family of six nonlinear optical (NLO) materials, A3B3CD2O14 (A = Sr, Ba, or Pb; B = Mg or Zn; C = Te or W; and D = P or V), has been synthesized and characterized. In addition to the synthesis and crystal structures, comprehensive characterization of these compounds includes second harmonic generation (SHG) measurements, theoretical calculations, infrared and diffuse reflectance spectroscopies, and thermogravimetric measurements. We find that all of the reported materials are SHG-active at 1064 nm, with responses ranging from 2.8 to 13.5 × KDP, and exhibit absorption edges in the mid- to deep-ultraviolet regime. By systematically replacing the A, B, C, and D cations, we are able to tune these properties and investigate the role of different NLO-active structural units in producing the SHG responses. Specifically, our electronic structure calculations reveal that the presence of Pb(2+) on the A-site and Te(6+) on the C-site is critical for generating a large SHG response. The synthesis and structure-property relationships described in this family of materials will enable the design and discovery of new NLO materials.

Oxychalcogenide BaGeOSe2: Highly Distorted Mixed-Anion Building Units Leading to a Large Second-Harmonic Generation Response

Oxychalcogenide BaGeOSe₂: Highly Distorted Mixed-Anion Building Units Leading to a Large Second-Harmonic Generation Response

K2Pb3(CO3)3F2 and KCdCO3F: Novel Fluoride Carbonates with Layered and 3D Framework Structures.

Two new mixed metal fluoride carbonates, KCdCO3F and K2Pb3(CO3)3F2, have been synthesized by solvothermal and solid-state techniques. KCdCO3F crystallizes in the acentric nonpolar space group P6̅m2, and its structure features a three-dimensional anionic framework in which the CdCO3 layers are further interconnected by bridging F(-) anions with the negative charge balanced by K(+) cations. K2Pb3(CO3)3F2 crystallizes in the centrosymmetric space group P63/mmc, and its structure exhibits a layered anionic skeleton featuring corner-shared PbO6F and PbO6F2 polyhedra. UV-vis diffuse reflectance spectroscopy studies show that the short-wavelength absorption edges of KCdCO3F and K2Pb3(CO3)3F2 are 227 and 287 nm, respectively. The second harmonic generation (SHG) measurement reveals that KCdCO3F is a phase-matchable material for generation of doubled-frequency light at both 532 and 266 nm, with a large SHG response of approximately 5.2 times that of KH2PO4 (KDP) at 532 nm and a moderate SHG response of approximately 0.75 times that of β-BaB2O4 (BBO) at 266 nm. Therefore, it is a promising UV material for fourth harmonic generation on a 1064 nm Q-switched Nd:YAG laser.

Design and Synthesis of the Beryllium-Free Deep-Ultraviolet Nonlinear Optical Material Ba₃(ZnB₅O₁₀)PO₄.

Access to the elusive deep-ultraviolet by direct second harmonic generation (SHG) enabled by a new beryllium-free zincoborate-phosphate crystal is reported. Ba3(ZnB5O10)PO4, exhibits large SHG responses at 1064 and 532 nm and a short 180 nm absorption edge. Centimeter-size crystals are grown, and quantum mechanical calculations demonstrate the key role played by ZnO4 tetrahedra in the enhanced optical responses.

Hybrid Germanium Iodide Perovskite Semiconductors: Active Lone Pairs, Structural Distortions, Direct and Indirect Energy Gaps, and Strong Nonlinear Optical Properties

The synthesis and properties of the hybrid organic/inorganic germanium perovskite compounds, AGeI3, are reported (A = Cs, organic cation). The systematic study of this reaction system led to the isolation of 6 new hybrid semiconductors. Using CsGeI3 (1) as the prototype compound, we have prepared methylammonium, CH3NH3GeI3 (2), formamidinium, HC(NH2)2GeI3 (3), acetamidinium, CH3C(NH2)2GeI3 (4), guanidinium, C(NH2)3GeI3 (5), trimethylammonium, (CH3)3NHGeI3 (6), and isopropylammonium, (CH3)2C(H)NH3GeI3 (7) analogues. The crystal structures of the compounds are classified based on their dimensionality with 1–4 forming 3D perovskite frameworks and 5–7 1D infinite chains. Compounds 1–7, with the exception of compounds 5 (centrosymmetric) and 7 (nonpolar acentric), crystallize in polar space groups. The 3D compounds have direct band gaps of 1.6 eV (1), 1.9 eV (2), 2.2 eV (3), and 2.5 eV (4), while the 1D compounds have indirect band gaps of 2.7 eV (5), 2.5 eV (6), and 2.8 eV (7). Herein, we report on the second harmonic generation (SHG) properties of the compounds, which display remarkably strong, type I phase-matchable SHG response with high laser-induced damage thresholds (up to ∼3 GW/cm(2)). The second-order nonlinear susceptibility, χS(2), was determined to be 125.3 ± 10.5 pm/V (1), (161.0 ± 14.5) pm/V (2), 143.0 ± 13.5 pm/V (3), and 57.2 ± 5.5 pm/V (4). First-principles density functional theory electronic structure calculations indicate that the large SHG response is attributed to the high density of states in the valence band due to sp-hybridization of the Ge and I orbitals, a consequence of the lone pair activation.

Pb7O(OH)3(CO3)3(BO3): first mixed borate and carbonate nonlinear optical material exhibiting large second-harmonic generation response.

The first borate carbonate UV nonlinear optical material Pb7O(OH)3(CO3)3(BO3) was hydrothermally synthesized, which features a (3,9)-connected IrSi3-like structure constructed by Pb7O(OH)3(BO3) units and carbonates. This compound exhibits a large second-harmonic generation (SHG) response about 4.5 times that of KH2PO4 (KDP), attributed to synergistic interactions between the stereoeffect of the Pb(II) cations and coparallel BO3 and CO3 triangles groups.

Near-resonant second-order nonlinear susceptibility in c-axis oriented ZnO nanorods

Near-resonant second-harmonic generation (SHG) in c-axis oriented ZnO nanorods is studied under the femtosecond laser with wavelength from 780 nm to 810 nm. A highly efficient SHG is obtained, which is attributed to the d131 component of the second-order nonlinear susceptibility. The largest d131 value is estimated to be 10.2 pm/V at the pumping wavelength of 800 nm, which indicates a large SHG response of the c-axis oriented ZnO nanorods in the near-resonant region. Theoretical calculation based on finite-difference time-domain simulation suggests a four-fold local-field enhancement of the SHG.

α-AgI3O8 and β-AgI3O8 with Large SHG Responses: Polymerization of IO3 Groups into the I3O8 Polyiodate Anion

Two new noncentrosymmetric isomeric silver polyiodates, namely, α-AgI3O8 (Pnc2) and β-AgI3O8 (I4), have been synthesized through the hydrothermal reactions of AgNO3 with I2O5. Both isomers exhibit layered structures that are constructed from I3O8– anions interconnected by Ag+ cations. The main structural difference between the two isomers lies in the different stacking fashions of [AgI3O8] layers along the c axis in order to meet the requirements of their space groups. Powder second-harmonic generation (SHG) measurements indicate that α-AgI3O8 and β-AgI3O8 are both phase-matchable materials with large SHG responses of approximately 9.0 and 8.0 times that of KH2PO4, respectively. UV–vis–NIR transmission spectra show that the cutoff absorption edges are 328 nm for α-AgI3O8 and 345 nm for β-AgI3O8. Thermal stability studies demonstrate that both isomers are thermally stable up to about 370 °C. Theoretical calculations based on DFT methods for the two AgI3O8 phases as well as the NaI3O8 analogue have been pe...