•Novel NLO chromophore based on 6-(pyrrolidin-1-yl)-1H-indole was synthesized.•Synthesized chromophore was characterized by 1H NMR,13C NMR, and MS spectra.•Thermal decomposition temperature could reach up to 275 °C.•An average electro-optic (EO) coefficient (r33) was 19 pm/V at wavelength 1310 nm.•Chromophore ZML-1 exhibits enhanced electro-optical activity.Novel nonlinear optical (NLO) chromophore based on 6-(pyrrolidin-1-yl)-1H-indole as the electron donor group was designed and synthesized. The molecular structure of this chromophore was characterized by 1H NMR spectra, 13C NMR spectra, and MS spectra. The delocalized energy level was estimated by UV–Vis. spectra. The thermal property was studied by thermogravimetric analysis (TGA). The poled films containing chromophores ZML-1 with a loading density of 10 wt% in amorphous polycarbonate (APC) afford an average electro-optic (EO) coefficient (r33) of 19 pm/V at 1310 nm. Compared to the reported aniline-based chromophore (r33 = 12 pm/V) analogues, chromophore ZML-1 exhibits enhanced electro-optical activity.Download high-res image (82KB)Download full-size image

•We studied a series of high-pressure behavior of Niobates.•The color of a complex compound often changes from blue to yellow under high-pressure conditions.•The luminescence properties and mechanism are discussed in detail.This work reports the high-pressure and high-temperature (HP-HT) synthesis of pure monoclinic phase of GdNbO4:Bi3+ phosphors. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence, and IR spectra were utilized to characterize the synthesized phosphors. The crystal structure distortions operated by the pressure leads to tunable emission varying from blue to yellow. A small increase of the probability of non-radiative energy transfer with increase of pressure is observed. It is shown that the efficiency of the energy transfer process is dependent on pressure. The calculations of CIE chromaticity coordinates were performed.

•Novel nonlinear optical polymer based on poly(aryl ether ketone) was prepared.•Such polymer showed us good water solubility.•Polymer PAEK-R have potential application in SHG imaging based on its low absorption spectral window at red light.Novel nonlinear optical polymer based on poly(aryl ether ketone) was designed and prepared. Such kind of materials showed excellent water solubility and thermal properties, its onset decomposition temperature can reach 314 °C; glass transition temperature can reach 170 °C. Though the nonlinear optical coefficients (d33) is not very large at 1310 nm, just about 13.9 pm/V; such kind of materials show us a low absorption spectral window at red and infrared light area (wavelength longer than 650 nm). Under the laser of 1310 nm, the morphology of the poled films can be detected by second harmonic generation (SHG) scanning microscopy.

•Four chromophore have been synthesized and systematically investigated.•There is a best match for donor and acceptor to improve nonlinear optical activity.•Chromophore d3 displayed excellent solubility and compatibility with matrix.•The poled film afforded a large r33 value of 37 pm/V after poling.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.

A new series of electro-optical dendrimers with asymmetric configurations was synthesized through a Cu-(I) catalyzed Huisgen reaction. The asymmetric dendrimers exhibited weaker chromophore dipole–dipole aggregations along with an improved response to the applied poling field than traditional dendrimers with the same type of chromophores. In order to systematically investigate the influence of the asymmetric structure on the physical properties, UV-vis spectroscopy and DFT calculations were carried out. Due to the asymmetric configurations, the obtained dendrimers exhibited weak dipole–dipole interactions compared with dendrimers with a flexible linker, furthermore they obtained a better alignment in the poling process. The asymmetric dendrimer AD-2 exhibited a 36 pm V−1 EO coefficient measurement, which was higher than the other two dendrimers and guest–host polymeric materials using the same chromophores.

•1,1′-binaphthyl-2,2′-diol with strong chiral structure was used as chiral molecule.•Effects of chiral additives on the electro-optical properties were discussed.•The interaction mechanism of chiral inducement was discussed and confirmed by SEM.Five polymer dispersed liquid crystal films were prepared using 1,1′-binaphthyl–2,2′-diol as the chiral additive with different concentration. These liquid crystal films showed us different electro-optical (EO) properties. Through theoretical analysis and discussion, the relationship between the electro-optical properties and the concentration of 1,1′-binaphthyl–2,2′-diol chiral additive was revealed. As the concentration of the chiral additive increasing, the mesh size of the liquid crystals would become smaller; so the liquid crystal molecules would become harder to be oriented in the electric field and therefore, the threshold voltage and saturation voltage would increase; the open state response times were also extended; the off state response times would be reduced.

•Principles and application of NLO effects in organic materials are reviewed.•Advantages of novel electron donors with multi-cyclic structures are introduced.•The influences of modified groups with different shapes and lengths are discussed in details.•The advantages and multi-functions of auxiliary donor are discussed.Organic electro-optic (EO) materials have been widely explored and used in the fabrication of microwave photonic devices. Their principal advantages are the follows: lower half-wave voltage, wider bandwidth, lower cost and more convenience of integration. Organic second order nonlinear optical (NLO) chromophores, as the core of the organic EO devices, define the key technological parameters: EO efficiency, long term stability, solubility and optical losses. In the present review article, the use of D–π–A chromophore molecules with polycyclic electron donors based on julolidinyl structure is reported and discussed. Significant improvement of electron donating ability and appropriate isolated effect are shown. Future perspectives of the application of such kind of NLO chromophores are considered.

In this brief review, nonlinear optical (NLO) chromophores widely used in electro-optic (EO) devices are summarized according to their EO coefficients. The advances of EO modulators based on organic materials in high bandwidth and low half wave voltages (Vπ) are discussed. The review is mainly devoted to the following aspects: (1) verification of high frequency operation and reduction of Vπ for all polymer waveguide EO modulators; (2) structures and advantages of sol–gel waveguide EO modulators; (3) principles and developments of silicon–organic hybrid (SOH) EO modulators. All the considerations are illustrated by the architecture of the devices and the used physical and chemical principles are explained in detail. Further means of improvement of their parameters are indicated.

•EO polymer with high chromophore loading and high glass temperature was designed and prepared.•Functional polymer was prepared by post functional reaction at the mild conditions.•Large r33 (50 pm/V @ 1310 nm) and good long term stability were achieved by this EO polymer.•Novel cycloaddition reaction was used to incorporate NLO chromophore into polymers.Polymers based on N-phenyl maleimide, N-4-propargyl methoxy phenyl maleimide and methyl methacrylate was synthesized. High glass temperatures 183, 179, 159 °C respectively for P1, P2 and P3 were achieved. EO polymer P3–C1, P3–C2 and P3–C3 with about 30 wt% chromophore loading density were prepared by attaching Chromophore C1, C2 and C3 to polymer P3 using copper-catalyzed Huisgen cycloaddition reactions in mild reaction conditions and high yield. Among the EO polymers, P3–C3 showed us the best solubility in normal solvents and suitable glass temperature. EO films based on EO polymer P3–C3 showed us large EO coefficient of 50 pm/V @1310 nm and good long-term stability, 85% EO activity was kept after annealing at 85 °C for 200 h.

•Nunchaku-like structure NLO materials with two NLO chromophores were designed and synthesized for the first time.•The novel structure endows the materials with large chromophore loading density that show large EO activity.•Nunchaku-like structure makes the chromophore have stronger interaction with polymers, endowing good long term stability.Dual D-Pi-A nunchaku-like structure chromophore was designed and synthesized to improve electro-optic (EO) materials׳ EO coefficients (r33) and long term stability by a simple doping system. The r33 values of poled APC/10% DIMER1 and APC/20% DIMER1 are 23 pm/V and 45 pm/V respectively. After annealed at 85 °C for 500 h, the poled film of APC/20% DIMER1 can retain more than 85% of its initial r33 value. All these characters showed us superior prospects of application in EO devices. Chromophore DIMER1 also showed us good thermal stability; its decomposition temperature (Td) was higher than 280 °C, which is enough for its application in the EO devices. Also chromophore DIMER1 had good solubility in amorphous polycarbonate (APC); it could be dissolved in APC at high loading density (25%).

•The main problems of organic EO materials which limit their commercial application were discussed in detail.•The Principles for auxiliary donors improving the EO activity and poling efficiency were reviewed and discussed.•The future development directions of organic EO materials were also discussed.Organic electro-optic (EO) materials have been widely studied and used in microwave photonic devices, due to their advantages in half-wave voltage, bandwidth, low cost and ease of integration. Nonlinear optical (NLO) chromophores, as the core of organic EO materials, can directly decide the characters of organic EO materials, including large EO activity, long term stability, solubility and optical loss. Auxiliary donors have attracted great attentions in NLO chromophores for their strong electron donating ability and significant isolation effect. This feature article describes the application of auxiliary donor in NLO chromophores, including the EO activities, optical characters, stability, crystal structures and machinability.

Two principally novel organic nonlinear optical chromophores (1 and 2) with flexible (n-hexyl group) or rigid isolated (benzyl group) group are designed and successfully synthesized. The prepared chromophores were characterized by MS, 1H-NMR and UV–Vis spectra. Their thermal stability was studied by thermal gravimetric analyzer and differential scanning calorimetry. Poled films of the chromophores doped in amorphous polycarbonate afford the maximum electro-optic tensor coefficient (r33) equal to 39 pm/V, 63 pm/V for chromophore 1 and chromophore 2, respectively at the wavelength 1,064 nm. The reason of so large differences between these two chromophores’ linear electrooptics coefficients were explained within a framework of performed quantum chemical calculations and it is crucially dependent on distances between the chromophore molecules and the polymer chains.

This article reports a synthesis a new class of nonlinear optical (NLO) polymer, containing 3-methyl-4-cyano-5-dicyanomethylidene-2-oxo-3-pyrroline (TCP) acceptor. TCP chromophore was synthesized and characterized by Uv-Vis absorption, 1H NMR, and mass-spectrometry. The titled polymer shows high thermal stability and large optical nonlinearity. A high glass transition temperature of 125°C was determined by DSC measurement, and measured electrooptical (EO) at wavelength 1.31 mm was equal to 37.4 pm/V. The order parameter of these films evaluated by absorption was equal to about 24%.

•Mn2+, Yb3+ doped Zn2GeO4 Uniform Nanorods.•Facile Microwave-assisted hydrothermal Synthesis.•The luminescence properties and mechanism are discussed in detail.Germanates have potential applications in electroluminescent fields. Herein, we report a simple strategy for the rapid synthesis of near-infrared (NIR) down-conversion Zn1.96-xGeO4+1/2x:Mn0.04Ybx phosphors using the microwave-assisted hydrothermal method. This method is facile, rapid, surfactant-free and environmentally friendly. In the Zn2GeO4 lattice, intrinsic defect transitions and Mn2+ ions act as broadband spectral sensitizers by absorbing UV–Vis (280–500 nm) photons and transferring the absorbed energy to Yb3+ centers in a cooperative down-conversion process. Efficient energy transfer is reflected by a sharp decrease in the excited state lifetime and green photoluminescence (PL) from tetrahedrally coordinated Mn2+ with increasing Yb3+ concentration. The possible formation mechanism for Zn1.96-xGeO4+1/2x:Mn0.04Ybx nanorods has been presented. PL spectroscopic characterizations show that pure Zn2GeO4 sample shows a blue emission due to defects, while Zn2GeO4:Mn2+ phosphors exhibit a green emission corresponding to the characteristic transition of Mn2+ (4T1 → 6A1) under the excitation of UV. The Yb3+ acceptor is then the source of NIR emission at a wavelength of ∼1000 nm. These phosphors are promising for applications in solar spectral down-conversion.We report a simple strategy for the rapid synthesis of near-infrared (NIR) down-conversion Zn1.96-xGeO4+1/2x:Mn0.04Ybx phosphors using the microwave-assisted hydrothermal method.