Second-order Nonlinear Optical Materials Research Articles

Tetracyanobutadienyl-Based Nonlinear Optical Dendronized Hyperbranched Polymer Synthesized via [2+2]Cycloaddition Polymer Postfunctionalization.

Dendronized hyperbranched polymers (DHPs) can provide advantages for both hyperbranched polymers and dendrimers, making them a promising structure platform for high-performance second-order nonlinear optical (NLO) materials. Herein, a new A3 +B2 -type DHP (HP2) is reported through facile and efficient [2+2]cycloaddition polymer postfunctionalization, in which tetracyanobutadienyl-based moieties are introduced as the main chromophores while isophorone-bridged moieties serve as the isolation chromophores. Benefiting from this unique hyperbranched structure design, the measured second-harmonic generation coefficient of HP2 can reach up to 96.6pmV-1 with high thermal stability, making it a good material candidate for second-order NLO applications.

Dendronized Hyperbranched Polymer: A New Architecture for Second-Order Nonlinear Optics

Organic/polymeric second-order nonlinear optical (NLO) materials, which rely on the poling-induced non-centrosymmetric arrangement of NLO chromophores, have played a very important role in laser technology and optical fiber communication, due to their ultra-fast response speed, excellent machining performance and low dielectric constant. However, the NLO chromophores have the large dipole moments with strong intramolecular charge transfer, which lead to the intermolecular electrostatic interactions to tend to the centrosymmetric arrangement and decrease the poling efficiency. Since the special three-dimensional spatial separation can minimize these strong intermolecular electrostatic interactions during poling process, dendrimers and hyperbranched polymers have been considered as better topology for the next generation of highly efficient NLO materials. In 2013, by the attachment of low generation dendrimers to the hyperbranched backbone, a new dendritic architecture of dendronized hyperbranched polymer (DHP) was proposed for improving the comprehensive performance of NLO materials. Recent results showed many advantages of DHPs in NLO field, such as easy syntheses, large NLO coefficients and high orientation stability, etc. In this review, the latest advancement of DHPs, including the design principle, synthesis, as well as their application as NLO materials is summarized. The new opportunities arising from DHPs are also summarized in the future perspective.

Prediction of Large Second Harmonic Generation in the Metal-Oxide/Organic Hybrid Compound CuMoO3(p2c)

Noncentrosymmetric hybrid framework (HF) materials are an important system in discovering new practical second-order nonlinear optical materials. We calculated the second harmonic generation (SHG) response of a noncentrosymmetric (NCS) organic–inorganic HF compound, CuMoO3(p2c) (p2c = pyrazine-2-carboxylate) to find that it exhibits the largest SHG response among all known NCS HF materials with one-dimensional helical chains. Further atom response theory analysis revealed that the metal atoms Cu and Mo contribute much more strongly than do nonmetal atoms in determining the strength of the SHG response, which is a novel example in nonlinear optical materials known to date.

NaGa3Se5: An Infrared Nonlinear Optical Material with Balanced Performance Contributed by Complex {[Ga3Se5]−}∞ Anionic Network

Second-order nonlinear optical (NLO) materials are extensively applied in laser-related techniques. For developing IR NLO materials, chalcogenides are the main candidates. Here, NaGa3Se5 was explored as inspired by its unique anionic structure. It crystallizes with the orthorhombic chiral P212121 structure, featuring 12 types of GaSe4 tetrahedra built into a three-dimensional {[Ga3Se5]-}∞ anionic network, representing a new NLO-functional motif. NaGa3Se5 exhibits large and phase-matchable NLO response 1.37 × AgGaS2. It has the largest band gap among the noncentrosymmetric A-MIII-Se (A = alkali metal; M = Ga, In) compounds. The NLO properties' origin is explored via theoretical analysis. The success of NaGa3Se5 contributes a practical case for exploring new NLO materials.

Metal oxyhalides: an emerging family of nonlinear optical materials.

Second-order nonlinear optical (NLO) materials have drawn enormous academic and technological attention attributable to their indispensable role in laser frequency conversion and other greatly facilitated applications. The exploration of new NLO materials with high performances thus has long been an intriguing research field for chemists and material scientists. However, an ideal NLO material should simultaneously satisfy quite a few fundamental yet rigorous criteria including a noncentrosymmetric structure, large NLO coefficients, desired transparent range, large birefringence, high laser damage threshold, and availability of a large-size single crystal. Therefore, the identification of promising compound systems, targeted design, and experience-based syntheses are crucial to discover novel NLO materials working in the spectral region of interest. As an important family of mixed-anion compounds, versatile metal oxyhalides containing metal-centered oxyhalide functional units ([MOmXn] (X = F, Cl, Br, and I)) are becoming a marvelous branch for interesting NLO materials. Especially, when the central metals are d0/d10 transition metals or heavy post-transition metals, a number of novel NLO materials with superior functionalities are expected. Our thorough review on the recent achievements of metal oxyhalides for NLO materials are divided into the fast-growing NLO metal oxyhalides with single type halogen anions and the newly identified NLO metal oxyhalides with mixed halogen anions. Here we mainly focus on the design strategy, structural chemistry, NLO-related properties, and structure–property correlation of the metal oxyhalides with relatively large NLO responses. We hope this review can provide an insight on the rational design and future development of emerging metal oxyhalides for NLO and other applications.

A New Nonlinear Optical Material with N(CN)2 - Anion.

Discovering new functional genes and developing high-performance materials are the goals being pursued by scientists. In this work, we successfully obtained a second-order nonlinear optical (NLO) material via the aqueous solution method, Y[N(CN)2 ]4 [NH(C2 H5 )3 ] ⋅ 3H2 O, which is the first NLO material with the anionic group N(CN)2 - . Remarkably, this material is not only strongly NLO-active at 1064 nm with a response of about 2.8 × KH2 PO4 , but also possesses a short UV absorption edge of 250 nm. In-depth first-principles calculations illustrate well that the optical properties are mainly from the strong interaction of N, C and Y atoms. This result indicates that the N(CN)2 - anion may be a new NLO functional gene. This work enriches the diversity of NLO functional genes and materials.

Superior Infrared Nonlinear Optical Performance Achieved by Synergetic Functional Motif and Vacancy Site Modulations

Achieving large phase-matchable (PM) nonlinear optical (NLO) efficiency and high laser-induced damage threshold (LIDT) in an infrared second-order NLO (IR NLO) material is the most crucial technica...

Coherently controlled quantum features in a coupled interferometric scheme

Over the last several decades, entangled photon pairs generated by spontaneous parametric down conversion processes in both second-order and third-order nonlinear optical materials have been intensively studied for various quantum features such as Bell inequality violation and anticorrelation. In an interferometric scheme, anticorrelation results from photon bunching based on randomness when entangled photon pairs coincidently impinge on a beam splitter. Compared with post-measurement-based probabilistic confirmation, a coherence version has been recently proposed using the wave nature of photons. Here, the origin of quantum features in a coupled interferometric scheme is investigated using pure coherence optics. In addition, a deterministic method of entangled photon-pair generation is proposed for on-demand coherence control of quantum processing.

ASb5S8 (A = K, Rb, and Cs): Thermal Switching of Infrared Nonlinear Optical Properties across the Crystal/Glass Transformation

Second-order nonlinear optical (NLO) switchable materials are eliciting increased interest because of their widespread optical applications. The stringent requirements of NLO efficiency, laser-indu...

Electronic structure and first hyperpolarizability of triple helicene compounds

Density functional theory (DFT) investigations on the reported triple helicene and four new substituted compounds are employed to aid in the design of nonlinear optical (NLO) materials with large first hyperpolarizability βHRS. The influences of different substituents were analyzed in terms of geometric and optoelectronic parameters such as energy gap, UV–vis absorption spectra, and electronic absorption energies. The investigation shows that the combination insertion of the donor unit and acceptor unit, especially the combination introduction of NH2 units at the R1 and R2 positions and NO2 units at the R3 and R4 positions, effectively reduces the band gap, makes the FMOs obvious spatial charge separation, broadens the absorption spectrum and produces a larger red shift, and obtains a larger βHRS value. Considering their strong NLO response, the studied compounds have the probability to be candidates used as excellent second-order NLO materials.

A Series of Pentanary Salt-Inclusion Chalcogenoborates Containing a B12Q12 (Q = S, Se) Cluster Exhibiting a Kleinman-Forbidden Frequency-Doubling Effect.

A series of pentanary chalcogenoborates (A3X)[InB12(InQ4)3] (A = K, Rb, Cs; X = Cl, Br, I; Q = S, Se) were obtained by high-temperature solid-state reactions. These salt-inclusion chalcogenides crystallize in the hexagonal space group P6322, a type of Kleinman-forbidden noncentrosymmetric structure. Their structures feature a [InB12(InQ4)3] open framework built by InQ6 octahedra and InQ4 tetrahedra consolidated B12 cluster, which accomodates octahedral cavities for XA6 units. They are second-harmonic generation active, and their optical properties were studied experimentally and theoretically. This work can evoke more interest in chalcogenoborate-based second-order nonlinear optical materials.

Second-order nonlinear optical and photoelectric properties of Zn4B6O12S

Recently, inorganic functional materials containing multiple anions have received extensive attention in view of their comprehensive physical performances, and chalcogenide borates are such one type of rarely explored novel materials. The combination of chalcogenides and borates are attractive in view of their advantages as potential second-order nonlinear optical materials. Here, borate sulfide Zn4B6O12S crystallized with the I4¯3m structure is synthesized using a solid-state reaction, and its structure features truncated octahedron. Its powder sample presents a largest second-harmonic generation around 1.9 × KDP at 1.604 μm, and its photocurrent is 2.1 μA/cm2, much higher than that of classical photoelectric material TiO2 (0.4 μA/cm2). Theoretical calculations on its electronic structure and optical properties are also performed.

Recent Achievements in Lone-Pair Cation-Based Infrared Second-Order Nonlinear Optical Materials

In the past 20 years, fundamental research on novel nonlinear optical (NLO) compounds has been extensively performed, which has built the important background for the application of NLO materials. ...

Investigation of the second-order nonlinear optical property of Sr6Sb6S17

Metal chalcogenides are extensively studied as infrared second-order nonlinear optical (NLO) materials. Among the candidates, ones containing cations with lone-pair electrons in the structure have received great interest in view of the lone-pair electrons’ special contribution to the NLO property. Here, we revisit such a sulfide Sb6Sb6S17 and study its NLO property, which represents a novel structure-type of NLO material. It exhibits phase-matchable second-harmonic generation activity, and the powder sample shows a laser-induced damage threshold (LIDT) around 3.2 times that of AgGaS2 when both have the particle sizes of 75–110 ​μm. Its optical energy gap is measured to be 1.92 ​eV and the powder sample has a transparency range from 0.65 to 25 ​μm. The electronic structure and optical property calculations are also performed.

Prediction of NLO response of substituted organoimido hexamolybedate: First theoretical framework based on p-anisidine adduct [Mo6O18(p-MeOC6H4N)]2-

The second-order nonlinear optical (NLO) responses and dipole polarizabilities of p-anisidine adduct (imido derivative of hexamolybdates/polyoxometalates/POMs/Cluster) are studied by means of time dependent density functional (TDDFT) calculations. A substantial molecular second-order NLO response has been noticed in these organic-inorganic hybrid compounds, particularly [Mo6O17 cis-(p-MeOC6H4N)2]2− (system 2) and [Mo6O18 p-MeOC6H4N]2- (system 1) having static second-order polarizability (βvec) calculated to be 1949.60 au and 1565.10 au respectively. Both p-anisidine and cis-(p-anisidine) are found to be preferred choice over the trans-(p-anisidine) adduct. There is a fair probability for these systems to be selected as efficient second-order nonlinear optical materials. The movement of charge transfer from p-anisidine to hexamolybdate cluster (D–A) along the y-axis suggests molybdenum cluster acts as an acceptor (A) whereas p-anisidine working as a donor (D) in all the studied systems which is responsible for NLO response in such adducts. An incremental increase in the computed βvec values were evaluated by incorporation of an electron donor (Metalloporphyrin) instead of p-anisidine. Furthermore, substitution of Fe over Zn in Metalloporphyrin cage has enhanced the optical nonlinearity. This research effort offers a significant understanding into metal (Fe/Zn) to metal (Mo) charge transfer through imido-linkage in hexamolybdates, which has been found to be an efficient mode to enhance NLO response as a prime example in modulation of optoelectronics.

ABa2Cl][Ga4S8] (A = Rb, Cs): Wide-Spectrum Nonlinear Optical Materials Obtained by Polycation-Substitution-Induced Nonlinear Optical (NLO)-Functional Motif Ordering.

Noncentrosymmetry (NCS) is a prerequisite for second-order nonlinear optical (NLO) materials. In this work, a new polycation-substitution-induced centrosymmetry (CS)-to-NCS transformation strategy was applied in CS RbGaS2, affording two novel NCS salt-inclusion chalcogenides: [ABa2Cl][Ga4S8] (A = Rb, 1; Cs, 2). Remarkably, they exhibit the key merits of both Vis and IR NLO candidates, including strong phase-matchable second harmonic generation intensities (10.4-15.3 × KH2PO4 at 1064 nm; 0.9-1.0 × AgGaS2 at 1910 nm), high laser-induced damage thresholds (11-12 × AgGaS2), and a wide transparent window. Their prominent NLO performances originate from the orderly packing of T2-supertetrahedral Ga4S10 motifs resulting from the template effect of acentric polycation [ClA2Ba3]7+. The CS-to-NCS transformation first realized by polycation-substitution-induced NLO-functional motif ordering provides an effective approach for designing new NLO materials.

A Correlation Study between Dendritic Structure and Macroscopic Nonlinearity for Second-Order Nonlinear Optical Materials

To study the effect of dendritic structure on the macroscopic nonlinearities, four types of dendritic nonlinear optical (NLO) materials containing the same isophorone-bridged chromophores are prepa...

Crystal chemistry, second-order nonlinear optical, and magnetic properties of Eu8Sn4Se20

Second-order nonlinear optical (NLO) materials in the middle infrared (MIR) region have attracted widespread interest in view of their importance and deficiency to the laser market’s requirement. Here, we report a new MIR NLO material Eu8Sn4Se20 (1), which represents a new structure type one and the pioneer of the (MII2MIVQ5)n (MII ​= ​divalent alkali-earth metal, Eu, Yb, Pb, and Sn; MIV ​= ​Si, Ge, Sn; Q ​= ​S, Se, Te. n ​= ​1, 2, 4) family. It demonstrates obvious second-harmonic generation (SHG) activity. Its optical band gap is determined to be 1.30 ​eV and its magnetic data exhibits antiferromagnetic-type behavior. Its electronic structure is performed as well.

Synthesis and Characterization of New Benzo[e]Indol Salts for Second-Order Nonlinear Optics

Organic second-order nonlinear optical materials are of great significance in the field of integrated photonics, optical data storage and optical information processing. In this work, two iodide salts with benzo[e]indol cations as electron-withdrawing groups were designed and synthesized, which are (E)-2-(4-hydroxy-3-methoxystyryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (1-TB) and (E)-2-(3,4-dihydroxystyryl)-1,1,3-trimethyl-1H-benzo[e]indol-3-ium iodide (2-TB). Under the irradiation of 1064 nm laser, the second harmonic generations of the 1-TB and 2-TB powders are 760 and 580 times that of urea, respectively. Among them, crystals of 1-TB are successfully grown by a slow cooling method without using seed crystals. Bulk crystal with a size of 8.0 × 3.0 × 1.0 mm3 and many submillimeter single crystals with excellent optical quality are obtained.

Growth and characterization of efficient second-order nonlinear optical material: N-(2-chlorophenyl)-(1-propanamide)

The crystals N-(2-chlorophenyl)-(1-propanamide) (NCP) appropriate for nonlinear optical (NLO) and electro–optic appliances were grown full-fledged by the slow cooling method. The solubility and metastable zone width range of NCP specimen were studied. The specimen crystallizes in the monoclinic crystal system with noncentrosymmetric space group of P21. The crystal morphology study also elucidates supplementary excellence of the as-grown NCP crystal. The optical precision in the whole visible region was found to be superior for NLO claim. The crystallinity of the full-fledged crystal is determined by etching and HRXRD. Laser harm threshold and photoluminescence studies delegate the grown crystal comprises extremely less imperfections. The mechanical deeds of NCP sample at assorted temperatures were examined to decide the hardness solidity of the grown specimen. The piezoelectric behavior and the comparative second harmonic generation for assorted particle sizes of the material were also deliberate. The third-order nonlinear ocular possessions of NCP crystal specimen were determined by Z-scan method. The optical homogeneity of the solitary crystal was assessed using customized channel spectrum technique. The thermal structures of NCP solitary crystal have been studied using photopyroelectric method. The half-wave voltage of the full-fledged crystal was intended from the electro–optic experimentation. Photoconductivity nature of the grown crystal outlined consummate inducing dipoles due to strong incident radiation and further revealed the nonlinear deeds of the grown material.