SHG Response Research Articles

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.

Indium selenide monolayer: a two-dimensional material with strong second harmonic generation

The In2Se3 monolayer may be a material with the strongest SHG response among IIIA–VIA semiconductors reported to date.

The second-harmonic generation intensification derived from localization conjugated π-orbitals in O22.

Molecular construction with π-conjugated groups is a favorable strategy to discover superior nonlinear optical (NLO) materials. Herein, a novel vanadium-carbonate compound K3[V(O2)2O]CO3 (KVCO), which combines two different π-orbital groups, delocalized (CO3)2- π-orbital groups and localized (O2)2- π-orbital groups, was synthesized. Benefiting from the well-arranged [V(O2)2OCO3] unit and dual-synergistic π-d-π interaction, KVCO has the largest second harmonic generation (SHG) effect (about 20 times that of KDP) among the current carbonate NLO materials. Moreover, first-principles calculation elucidated the coupling enhancement mechanism between (CO3)2-, (O2)2- and VOn groups.

Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

ABSTRACTLanthanide borates containing post transition metal main group elements, including Ga(III), Ge(IV), Sb(V) and Te(VI), as well as lanthanide salts of the oxyanions of lone pair cations, such as I(V), Se(IV) and Te(IV), were reviewed. The post transition metal main group elements in lanthanide borates adopt octahedral or tetrahedral geometry only. In the structure of lanthanide galloborates, only octahedral GaO6 was found while both octahedral GeO6 and tetrahedral GeO4 appeared in borogermanates. The fifth period elements Sb(V) and Te(VI) prefer octahedral coordination geometry in lanthanide borates system. The second groups introduced to lanthanide oxyanions of lone pairs are mainly focused on d0 TM units, such as WO4 tetrahedron, VO5 square pyramid or MoO6 octahedron, and rigid tetrahedral groups like sulfate SO4, silica SiO4 or selenate SeO4 units. Divalent cations like Pb(II) and magnetic ions of Cu(II) or Mn(II) were also included. The structure chemistry of lanthanide ions in these systems is rich. Coordination numbers from six to ten are discovered, yielding a wide range of coordination geometries including the pentagonal bipyramid, square antiprism, metabidiminished icosahedron, tricapped trigonal prism, capped triangular cupola, etc. The connectivity modes between the Ln polyhedra are miscellaneous, from 3D network, to 2D layer, 1D chain, tetramer, trimer, dimer and finally monomer. A number of compounds display NCS structures and strong SHG response, and many lanthanide compounds exhibit good luminescent properties in visible and IR region.

Optical second harmonic generation analysis of the atomically stepped Au/TiO2 (320) interface

A gold thin film with the thickness of 2nm on the TiO2(320) substrate has been fabricated in a UHV chamber at the pressure of 2x10-7 Torr. We observed the second harmonic response from the Au/TiO2(320) interface and bare TiO2(320) as a function of the rotation angle around the surface normal by using of a pulsed Nd3+:YAG laser as the excitation light at a photon energy of 1.17 eV and 2.33 eV. An isotropic response was observed from both samples for 1.17 eV photon energy excitation. In contrast, an anisotropic response was observed from both samples for 2.33 eV photon energy excitation. From the Au/TiO2(320) interface, anisotropic structure of SHG response was observed in the [2¯30] direction for Pin/Pout polarization combination. Nonlinear susceptibility elements were decomposed and two groups of them were assigned as the main contribution from the step and terrace of the vicinal TiO2 surface.

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.

Effect of the magnetic field on the nonlinear optical rectification and second and third harmonic generation in double [formula omitted]-doped GaAs quantum wells

In this paper we are reporting the computation for the Nonlinear Optical Rectification (NOR) and the Second and Third Harmonic Generation (SHG and THG) related with electronic states of asymmetric double Si-δ-doped quantum well in a GaAs matrix when this is subjected to an in-plane (x-oriented) constant magnetic field effect. The work is performed in the effective mass and parabolic band approximations in order to compute the electronic structure for the system by a diagonalization procedure. The expressions for the nonlinear optical susceptibilities, χ0(2), χ2ω(2), and χ3ω(3), are those arising from the compact matrix density formulation and stand for the NOR, SHG, and THG, respectively. This asymmetric double δ-doped quantum well potential profile actually exhibits nonzero NOR, SHG, and THG responses which can be easily controlled by the in-plane (x-direction) externally applied magnetic field. In particular we find that for the chosen configuration the harmonic generation is in the far-infrared/THz region, thus and becoming suitable building blocks for photodetectors in this range of the electromagnetic spectra.

Synthesis, crystal structure, optical property and theoretical studies of a noncentrosymmetric telluromolybdate CoTeMoO6

Polycrystalline CoTeMoO6 has been synthesized, and CoTeMoO6 crystals have been grown by spontaneous crystallization. Band structure, density of states, charge density, electronic structures and optical properties of CoTeMoO6 crystal were calculated by using a first-principles method for the first time. Optical and nonlinear optical properties of CoTeMoO6 crystal were measured. Structure and charge density analyses indicate that cleavage maybe exist in CoTeMoO6 crystal. The experiment results of optical properties show that a strong absorption band exhibits at 458–692 nm in the visible region. The absorption band plays an important role in the coloration of CoTeMoO6 crystal. The SHG responses of CoTeMoO6 with a 1.06 μm laser is much weaker than that of KDP, which can be ascribed to the absorption band caused by spin-allowed d-d transitions of Co2+ ions. Thus CoTeMoO6 crystal is not suited to be used as nonlinear optical material in the Vis-NIR region.

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.

Na4Ca[B4O5(OH)4]3·14H2O: An Acentric Supramolecular Framework Borate Based on [B4O5(OH)4]2− Cluster Units

A new mixed-metal tetraborate, Na4Ca[B4O5(OH)4]3·14H2O (1), with an acentric structure has been synthesized under mild solvothermal conditions and characterized by powder X-ray diffraction, thermogravimetric analysis, IR and UV–Vis spectroscopy, nonlinear optical determination and single crystal X-ray diffraction. 1 crystallizes in hexagonal space group P-62c (No. 190) with the unit cell parameters: a = 11.2896 (6) A, c = 15.8360 (9) A, V = 1748.0 (2) A3, and Z = 1. The compound features two types of layered networks, a borate network with kgm topology and a Na–O–Ca network with hcb topology, which are alternately arranged generating a 3D framework with straight channels. Powder second-harmonic-generating measurement indicates that compound 1 presents a SHG response of ~0.9 times that of KDP (KH2PO4), with the UV cut-off edge below 240 nm, making 1 a potential UV NLO material.

Synthesis, crystal structure, and optical properties of the noncentrosymmetric sulfide Ce8Sb2S15

The new noncentrosymmetric sulfide Ce8Sb2S15 has been prepared at 1223K in an evacuated silica tube. It crystallizes in the RE8Sb2S15 (RE=La, Pr, Nd) structure type with a=15.7871(6)Å, c=19.7992(16)Å, V=4934.6(5)Å3. The structure contains the discrete [SbS3]3– trigonal pyramids, which are packed in a noncentrosymmetric pseudolayer motif perpendicular to the c direction and lead to a polar structure. The Ce3+ cations and S2– anions located between them. It exhibits a weak SHG response in the IR region. UV/Vis diffuse reflectance spectroscopy study indicates that the optical gap of Ce8Sb2S15 is about 1.99eV, showing a red shift with respect to the corresponding ternary sulfides: La8Sb2S15, which was attributed to the allowed electronic transfer from the narrow Ce 4f level to the conduction band, mainly built from the empty Ce 5d orbitals.

(H3O)Ca2Zn3.5(PO4)4 and Ba2Cd3(PO4)2(HPO4)2: Syntheses, crystal structures and characterizations of two mixed metal phosphates

Two new phosphates, non-centrosymmetric (NCS) (H3O)Ca2Zn3.5(PO4)4 and centrosymmetric (CS) Ba2Cd3(PO4)2(HPO4)2 have been prepared by hydrothermal reactions. The single-crystal X-ray structural analyses have shown that they crystallized in space group P−421c and P21/c, respectively·(H3O)Ca2Zn3.5(PO4)4 features a three-dimensional (3D) network structure composed of ZnO4 and PO4 tetrahedra that are interconnected via corner-sharing, forming 1D channels of 6-MRs and 8-MRs which are filled by Ca2+ and H3O+ cations, respectively. Ba2Cd3(PO4)2(HPO4)2 features a layered [Cd3(PO4)2(HPO4)2]4- composed of 1D chain of edge-sharing CdO6 octahedra that are further bridged by PO4 tetrahedra with Ba2+ cations filling the interlayer spaces. Luminescent studies suggest that (H3O)Ca2Zn3.5(PO4)4 emits blue light. Optical diffuse reflectance spectra show the experimental band gaps for (H3O)Ca2Zn3.5(PO4)4 and Ba2Cd3(PO4)2(HPO4)2 are 5.67eV and 5.68eV, respectively. The UV cut-off edge of title compounds are around at 218nm·(H3O)Ca2Zn3.5(PO4)4 exhibits a very weak SHG response.

Synthesis and nonlinear optical property of polycrystalline MnTeMoO6

Polycrystalline MnTeMoO6 powder has been synthesized by a new approach that MnO2 is used as the manganese source. The transformation mechanism of manganese ions in the new approach has been discussed. The nonlinear optical property of polycrystalline MnTeMoO6 has been investigated, and compared with single-crystalline samples. The transformation Mn4+ → Mn2+ may be formed directly without stable intermediates, and TeO2 may serve as catalyst. The SHG response of polycrystalline MnTeMoO6 powder is worse than that of single-crystalline powder in the same particle size distribution as its pseudo-size. The results indicate that it should pay special attention with the pseudo-size of polycrystalline powder when the potential nonlinear optical materials are screened by powder second harmonic generation measurements.

The activity of lone pair contributing to SHG response in bismuth borates: a combination investigation from experiment and DFT calculation.

Second harmonic generation (SHG) response is one of the most essential properties of nonlinear optical (NLO) materials. To achieve relatively strong SHG response, a feasible strategy is to introduce stereochemically active lone pair (SCALP) cations, such as Bi3+. NLO materials with Bi3+ usually exhibit a huge difference in SHG response, the inner correlation between the activity of SCALP and SHG response still being unclear owing to the lack of quantization estimation of the intensity of SCALP. Based on the calculation results of density functional theory (DFT), we develop a theoretical method to compute the intensity of the Bi-6s SCALP, which could describe the stereochemical behavior and exert significantly influences on some apparent optical properties, such as SHG response. Using the method, we further analyze a series of bismuth borates which exhibit an apparent hierarchy in SHG response: BiB2O4F (12 × KDP), α-BiB3O6 (8.2 × KDP), Bi2ZnOB2O6 (4 × KDP), CaBi2B2O7 (2 × KDP), and Bi2B8O15 (1.2 × KDP). Combining the experimental measurements for the SHG responses, electronic structure analysis and the real-space atom cutting method, we explore the mechanism of the hierarchy in SHG response.

LiRb2PO4: a new deep-ultraviolet nonlinear optical phosphate with a large SHG response

LiRb2PO4(LRPO) possesses a very short UV cut-off edge (<170 nm), and a large SHG response (2.1 × KDP) and is phase-matchable.

Co-ligand tuned pyrimidine-2-carboxylate Mn(ii) complexes from a 2D 63 layer to an interpenetrated srs-net.

A 63 2D layer complex [Mn3Cl3(L3)]n·H2O (1) (L = pyrimidine-2-carboxylate) was obtained by assembling 2-cyanopyrimidine and manganese chloride, in which the L ligands were generated in situ. In 1 six-membered Mn rings were constructed from MnII ions and L ligands, which were connected to each other by double chloride anions affording a 2D layer. When the chloride anions in 1 were substituted partly by formate, [Mn4Cl3L4(HCO2)]n (2) was obtained. In 2, the L ligands bridge MnII to give a 1D chain, which was further connected by the double chloride anions and Cl/formate bridges to form a two-fold interpenetrated srs-net. Interestingly, 2 exhibits an obvious SHG response of approximately 0.8 times that of KDP. Furthermore, 2 is an antiferromagnet with a field induced spin flop transition.

Theoretical investigation on the balance between large band gap and strong SHG response in BMO4(M = P and As) crystals

A suitable balance between large band gap and strong SHG response is obtained due to the strong sp hybridization.

Synthesis and characterization of inorganic nonlinear optical material: Potassium sodium hydroxide borate hydrate (KSB) single crystal

Using the slow evaporation solution growth technique, a new compound of potassium sodium hydroxide borate hydrate (KSB) single crystal has been prepared. The title compound crystallized in a noncentrosymmetric hexagonal system with P6¯2c space group was confirmed by single crystal X-ray diffraction. The functional group was determined by using FTIR spectrum. The absorption spectrum shows an absorption edge at 265nm with a band gap of 4.68eV. The melting point of the material was found to be 105°C using TG/DSC analysis. The frequency dependence of dielectric, ac conductivity and the relaxation of an ionically conducting crystal have been studied for different temperatures. Nonlinear optical measurement of the grown crystal can displays a SHG response which is almost equivalent to that of KDP.

Hierarchical active factors to band gap and nonlinear optical response in Ag-containing quaternary-chalcogenide compounds

In this research work, Ag-containing quaternary-chalcogenide compounds KAg2TS4 (T=P, Sb) (I-II) and RbAg2SbS4 (III) have been studied by means of Density Functional Theory as potential IR nonlinear optical materials. The origin of wide band gap, different optical anisotropy and large SHG response is explained via a combination of density of states, electronic density difference and bond population analysis. It is indicated that the different covalent interaction behavior of P-S and Sb-S bonds dominates the band gap and birefringence. Specifically, the Ag-containing chalcogenide compound KAg2PS4 possesses wide band gap and SHG response comparable with that of AgGaS2. By exploring the origin of the band gap and NLO response for compounds KAg2TS4 (T=P, Sb), we found the determination factor to the properties is different, especially the roles of Ag-d orbitals and bonding behavior of P-S or Sb-S. Thus, the compounds KAg2TS4 (T=P, Sb) and RbAg2SbS4 can be used in infrared (IR) region.