Order Nonlinear Optical Chromophores Research Articles

The Progress in the Field Auxiliary Donors and their Application in Novel Organic Second-Order Nonlinear Optical Chromophores

Conversion efficiency between electrical and optical signals is very important for the development of modern information technologies. Due to their advantages in half-wave voltage, bandwidth, cost and integration, as well as organic electro-optic (EO) parameters, these materials are widely studied and used in microwave photonic devices. Second order nonlinear optical (NLO) chromophores, as the core of organic EO materials have an increasing interest in this branch. Auxiliary donors present a new direction for the design and improvement of organic NLO chromophores. In this short review, the advantages, theoretical calculations and experimental results of auxiliary donors are reviewed and discussed in detail.

Improved electro-optical property by introducing stronger acceptor to thermal stable chromophores using modified julolidine as donor

Abstract Two novel second order nonlinear optical chromophores based on large steric hindrance group modified julolidine donor and CF3-Ph-TCF acceptor linked via thiophene bridge were synthesized and characterized. Density functional theory (DFT) calculations suggested that the molecular quadratic hyperpolarizability (β) value of CF3-Ph-TCF based chromophore is 18.1% and 18.8% larger than that of TCF based chromophores, respectively. The optimized structure shows that chromophore z4-3f with stronger acceptor and larger modification group presents the best molecular configuration. UV–Vis results show great red-shift about 130 nm for chromophores z2-3f and z4-3f compared with z2 and z4. According to cyclic voltammetry measurements, chromophores z2-3f and z4-3f showed lower energy gap indicating better intramolecular charge-transfer (ICT) transition. Especially, chromophore z4-3f displayed good thermal stability with onset decomposition temperature at about 265 °C. The poled films containing 25 wt% chromophores in amorphous polycarbonate (APC) afforded electro-optical(EO) coefficients (r33) of 125 and 128 pm/V at 1310 nm. Further, film containing larger group modified chromophore was more efficient to realize good EO property with an order parameter (Φ) up to 18.4%. It's confirmed that chromophores z2-3f and z4-3f, which had good thermal stability and high r33 values after poling in films, was a promising candidate for practical use.

Synthesis and nonlinear optical properties of novel conjugated small molecules based on indole donor

Abstract Buchwald-Hartwig amination of aryl halides with solvent-free condition was used for the preparation of electron donors with high density of electron cloud. Organic second order nonlinear optical chromophore ZML-c based on this electron donor was designed and synthesized. And chromophore ZML-ref without modified groups was also prepared as the contrast. Their delocalized energy levels were estimated by UV–Vis. spectra. Their thermal properties were studied by thermogravimetric analysis (TGA). Obviously, chromophore ZML-c showed lower delocalized energy levels and lower thermal decomposition temperature (just about 160 °C). The poled films showed the largest electro-optic (EO) coefficients of 23.5 pm/V and 10.6 pm/V respectively for chromophore ZML-c and ZML-ref. These results indicate that effective modification in indole ring may be a promising way to drastically change the electro-optical features of the titled compounds and show a direction of designing new electron donor in the field of nonlinear optical materials.

Design and preparation of side chain electro-optic polymeric materials based on novel organic second order nonlinear optical chromophores with double carboxyl groups

Organic second nonlinear optical chromophore GL-COOHs with two carboxyl groups are designed and synthesized in this paper. The structure of chromophore GL-COOHs are characterized by mass spectrum and nuclear magnetic resonance spectroscopy. The first order hyperpolarizability is studied by theoretical calculation, which is similar to the famous FTC chromophore. Thanks to the double carboxyl group structure, novel side chain polyester electro optic polymers are prepared based on chromophore GL-COOHs. Their Tgs are around 110 °C, which is high enough for keeping the long term stability of their electro optic activities. Their Tds are above 239 °C, which is high enough for the devices preparing process. Else, the largest d33 values are about 29.3, 43.6 and 63.1 pm/V for polymer GL-S-1, GL-S-2 and GL-S-3 respectively. Interestingly, there is a linear relation between chromophore loading density and d33 values.

The influence of different donor/acceptor matches on chromophore's nonlinear optical activity

Abstracts In this work, a series of novel second order nonlinear optical chromophores modified by heteroatom-groups in electron-donor has been synthesized and systematically investigated. The resulting nonlinear optical chromophores exhibited both good thermal stability and good solubility in common organic solvents. UV–Vis spectra and density functional theory calculations were carried out to investigate the influence of heteroatom-groups on the electro-optic activities. The results revealed that increasing the electron-donor strength will not always improve the nonlinear optical activity of chromophore. There is a best match for electron-donor and acceptor. As to electro-optic activities, the doped polymer film- d3 displayed the highest electro-optic coefficient value of 37 pm/v at the doping concentration of 25 wt%. These results indicated that the nonlinear optical activities could be enhanced by finding the best match for electron-donor and acceptor in chromophore design.

Introduction of N atom into the conjunction system of organic second order nonlinear optical chromophores: An effective method for improving the photochemistry stability

Abstract Organic nonlinear optical chromophores with different number of N atoms were prepared and characterized. Their nonlinear optical character was studied both by theoretical calculation and second harmonic generation experiment. Chromophore ZJ1 showed us the largest d33 value of 87.5 pm/V. More importantly, the photochemistry stability of the chromophores was also studied in details. Chromophores with N atoms in the conjugated system showed us better photochemistry stability than the traditional chromophores.

Synthesis and characterization of two novel second-order nonlinear optical chromophores based on julolidine donors with excellent electro-optic activity

Second order NLO chromophores with julolidine donor.

Synthesis and characterization of one novel second-order nonlinear optical chromophore based on new benzoxazin donor

Abstract One novel second order nonlinear optical chromophore based on benzoxazin donor and tricyanovinyldihydrofuran acceptor linked together via thiophene bridge has been synthesized and characterized. According to cyclic voltammetry measurement, chromophore Z showed low energy gap. In addition, chromophore Z displayed good thermal stability with the onset decomposition temperature over 221 °C. The electro-optic coefficient of a poled film containing 25 wt% of chromophore Z doped in polymethylmethacrylate afforded a value of 64 pm/V at 1310 nm. The result showed that chromophore Z , which had good thermal stability and high r 33 values after poling in films, was a promising candidate for practical use.

Synthesis and characterization of novel AZO chromophore with multi hydroxyl groups

Novel organic second order nonlinear optical chromophore with 4,4′-(5-(bis(2-hydroxyethyl)amino)-1,3-phenylene)bis(oxy)dibutan-1-ol as electron donor and azo thiophene as π-electronic bridge was synthesized and characterized by 1H NMR spectra and mass spectra. After the introduction of four hydroxyl groups to the electron donor, the solubility of chromophore Z1 in water was improved greatly (0.5 g). Else, the solubility of chromophore Z1 in common organic solvents was still very good. The thermal decomposition temperature was above 250 °C, which was high enough for its application in both the preparation of optoelectronic devices and Second harmonic generation imaging. Electro-optical films prepared by chromophore Z1 showed us the largest second-order nonlinear optical coefficient was about 85 pm/V, which was large enough for the detection of second harmonic generation signal in water solution. Else, the photochemical stability of chromophore Z1 was also studied; the advantage of chromophore with azo bond was very obvious for improving the photochemical stability of organic second order nonlinear optical chromophores.

Using functionalized nonlinear optical chromophores to prepare NLO-active polycarbonate films

Abstract Novel functionalized second order nonlinear optical (NLO) chromophores have been prepared with functionalized aniline as electron donor, thiophene or isophorone as a π-spacer and 1,3-diethyl-2-thiobarbituric acid as electron acceptor. The films prepared from dyes with alkylsilyl bulky groups gave better performance than the corresponding non functionalized chromophores due to the reduction of the intermolecular electrostatic interactions. The incorporation of chromophores 4 and 10 in a polycarbonate matrix allowed the preparation of good optical-quality films. Nonlinear coefficients d 33 and d 31 as high as 17 and 5.6 pm V −1 , respectively, were obtained. Moreover, the temporal stability of these host-guest films was confirmed up to eight months (>80%).

A nunchaku-like nonlinear optical chromophore for improved temporal stability of guest–host electro-optic materials

Abstract A novel nunchaku-like organic second order nonlinear optical chromophore containing a D–π–A backbone and a rigid biphenylene unit was prepared. The UV–vis absorption spectra studies demonstrated that the large rigid structure could suppress dipole–dipole interactions effectively. The electro-optic coefficient of a poled film containing 20% wt of the new dye doped in amorphous polycarbonate afforded a value of 39 pm/V at 1310 nm. Compared with results obtained from a similar D–π–A chromophore without the rigid isolated group, the new dye gave better performance. Moreover, the electro-optic film prepared with the new dye gave greater temporal stability, compared to a similar D–π–A doped poled film that was reported previously. These results indicated that the introduction of a biphenylene group could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores.

New Figure of Merit for Tailoring Optimal Structure of the Second Order NLO Chromophore for Guest-Host Polymers

Reliability to forecast SHG efficiency using two sets of non linear optical (NLO) chromophore figures of merit (FOM) was tested. One of them predicts that SHG efficiency d 33 of the poled guest-host polymer is proportional to ground state dipole ∼ μg, another to ∼ 1/μg. Correlation of maximal achieved second order NLO efficiency of the PMMA based systems containing eight dimethylaminobenzylidene-1, 3-indandione (DMABI) related chromophores with proposed FOM have been analyzed. The best correlations were obtained with second set of FOM, especially if high dipole moment (μg > 7D) chromophores are included in analysis.

Effects of processing on all‐optical poling characteristics of guest‐host azo‐dye polymer thin films

AbstractSeveral kinds of azo‐dye polymer films of the guest‐host system were prepared by the spin‐coating method. Four disperse red (DR) dyes of DR1, DR19, DR54 and DR73 were chosen as second order nonlinear optical active chromophores with polymer matrixes such as poly (methyl methacrylate) PMMA or polycarbonate (PC). The processing conditions such as heat‐treatment, substrate, and film storage condition on all‐optical poling characteristics of azopolymers have been investigated. It is found that the second harmonic generation intensity is very sensitive to the chromophores and processing parameters. Some explanations have been proposed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Multifunctional Nickel-Bisdithiolate Complexes with trans -4-[2-(1-Ferrocenyl)Vinyl]-1-Methylpyridinium Cation

Nickel-bisdithiolate complexes with a ferrocene-containing 2nd order nonlinear optical chromophore as a cation, (FcCH=CHPyMe)[NiL 2 ] where L=dmit (1a), dddt (1b) and debt (1c) were synthesized by the cation exchange reaction. In the X-ray crystal structure of complex (1a), no intrastack but interstack S…S interactions less than 3.7 Å are observed. This complex was revealed to be an insulator at room temperature. However, (FcCH=CHPyMe) x [Ni(dmit) 2 ] (0<x<1) (3) needle grown in an H-type electrochemical cell shows semiconductor behavior ( E a =106 meV) over the temperature range measured (30∼300 K) with σ RT =1 Ω −1 cm −1 . The electronic transition at UV-vis-NIR region was measured for the nickel complexes and discussed.

Multifunctional Nickel-Bisdithiolate Complexes with trans -4-[2-(1-Ferrocenyl)Vinyl]-1-Methylpyridinium Cation

Nickel-bisdithiolate complexes with a ferrocene-containing 2nd order nonlinear optical chromophore as a cation, (FcCH=CHPyMe)[NiL 2 ] where L=dmit (1a), dddt (1b) and debt (1c) were synthesized by the cation exchange reaction. In the X-ray crystal structure of complex (1a), no intrastack but interstack S…S interactions less than 3.7 A are observed. This complex was revealed to be an insulator at room temperature. However, (FcCH=CHPyMe) x [Ni(dmit) 2 ] (0<x<1) (3) needle grown in an H-type electrochemical cell shows semiconductor behavior ( E a =106 meV) over the temperature range measured (30∼300 K) with σ RT =1 Ω −1 cm −1 . The electronic transition at UV-vis-NIR region was measured for the nickel complexes and discussed.

Enhanced electro-optic poling in guest–host systems using conductive polymer-based cladding layers

We report on the development of conductive polymer-based cladding layers for use in multilayered electro-optic (EO) device structures. The waveguide claddings used in these studies were based on blends formed from the conductive polymer poly (ethylene dioxythiophene) with poly (vinylalcohol). Thin films of the blended materials were spun to form cladding layers having tunable conductivity and optical absorption. We tested these materials using a well-known guest–host core layer to determine their effect on the polar alignment of second order nonlinear optical chromophores. The claddings tested were shown to provide a large effective poling field across the active layer, and thus produced larger EO coefficients than systems having comparable, but more highly resistive, claddings.

Highly Efficient, Thermally and Chemically Stable Second Order Nonlinear Optical Chromophores Containing a 2-Phenyl-tetracyanobutadienyl Acceptor

Highly Efficient, Thermally and Chemically Stable Second Order Nonlinear Optical Chromophores Containing a 2-Phenyl-tetracyanobutadienyl Acceptor

Novel photorefractive sol-gel materials

We have developed new photorefractive media based on hybrid organic-inorganic materials containing a charge transporting (CT) molecule either as side-chain or main-chain substituents on the silica backbone. Second order nonlinear optical (NLO) chromophores were introduced either as side chain or as guest units. These materials were prepared by the sol-gel process in the form of thin films of a few μm-thick. NLO and photorefractive properties have been evaluated using electro-optic measurements, two beam coupling experiments and photoconductivity measurements.

New Developments in Thermally and Chemically Stable Nonlinear Optical Chromophores for E-O Device Applications

ABSTRACTA new class of second order nonlinear optical chromophores resulted from the replacement of the most reactive CN group in tricyanovinylthiophene derivatives with aryl units, have been designed and synthesized. It was shown that these chromophores provide excellent tradeoffs among many relevant properties such as molecular nonlinearity, linear absorption at 830 nm, inherent thermal stability, chemical stability in processing solvents as well as host polymer matrices at high temperatures and attenuation at 830 nm.

Observation Of Photorefractive Effect In A Second Order Nonlinear Optical Chromophore Functionalized Polythiophene Derivative

ABSTRACTWe report the observation of photorefractive (PR) effect in a solution processable, thiophene copolymer with a side chain nonlinear optical (NLO) chromophore, poly(3- octylthiophene-co-N-(3-thenyl)-4-amino-2-nitrophenol) [POMDT]. The copolymer exhibits moderately fast photoconductivity. When doped with second order NLO active azo dye, this copolymer exhibited large second order NLO activity, and low asymmetric two beam coupling (TBC) gain. Enhanced TBC gain was observed, when this composite material was plasticized. The observed photorefractive response time is of the order of seconds. The slower response is attributed to the presence of large volume fraction of the plasticizer in the composition, which reduces the charge carrier mobility. The results from photoconductivity, second harmonic generation and two beam coupling experiments are discussed.