Electro-optic Coefficients Of Poled Films Research Articles

Systematic Study on Nonlinear Optical Chromophores with Improved Electro-Optic Activity by Introducing 3,5-Bis(trifluoromethyl)benzene Derivative Isolation Groups into the Bridge

A series of novel chromophores A, B, C, and D, based on the julolidinyl donor and the tricyanofuran (TCF) and CF3-tricyanofuran (CF3-Ph-TCF) acceptors, have been synthesized and systematically investigated. The 3,5-bis(trifluoromethyl)benzene derivative isolation group was introduced into the bridge in the chromophores C and D. These nonlinear optical chromophores showed good thermal stability, and their decomposition temperatures were all above 220 °C. Density functional theory (DFT) was used to calculate the energy gaps and first-order hyperpolarizability (β). The macroscopic electro-optic (EO) activity was measured using a simple reflection method. The highest EO coefficient of poled films containing 35 wt% of chromophore D doped in amorphous polycarbonate afforded values of 54 pm/V at 1310 nm. The results indicate that the 3,5-bis(trifluoromethyl)benzene isolation group can suppress the dipole-dipole interaction of chromophores. The moderate r33 value, good thermal stability, and good yield of chromophores suggest their potential use in the nonlinear optical area.

The influence on properties with different conjugated direction of phenoxazine and phenothiazine-based chromophores for organic nonlinear optical materials

A serial of phenoxazine and phenothiazine based organic chromophores were synthesized with facile routes. Then these chromophores were applied in organic nonlinear optical materials to study the effect of different conjugated direction, extra phenyl ring and alkyl chain on the decomposition temperature, energy level, photophysical properties through Uv–vis spectral, density functional theory calculations. The electro-optic coefficient of poled films containing these chromophores doped in amorphous polycarbonate afforded the largest values of 19 pm/V, 49 pm/V and 23 pm/V at 1310 nm for chromophores B, L1 and L2 respectively. To our regret, chromophore A is not stable enough for test. The geometries of the chromophores were optimized to gain insight into the molecular structure and electron distribution. These results showed that when the phenyl ring was added in chromophore A, B, nearly 90°of the dihedral angle between PTZ and phenyl ring unit leads to the intramolecular charge transfer transition (HOMO-LUMO) being prohibited and showed a smaller hyperpolarizability (β) value.

Enhanced electro-optic activity and thermal stability by introducing rigid steric hindrance groups into double-donor chromophore

A series of novel chromophores based on same bis (N,N-diethyl) aniline donor have been synthesized and systematically characterized. Chromophores with rigid steric hindrance groups showed superb thermal stabilities with high thermal decomposition temperatures above 260 °C. Besides, compared with the chromophore (y2) without isolation group, these new chromophores show better intramolecular charge-transfer absorption. Most importantly, the introduction of rigid steric hindrance groups can effectively reduce dipole–dipole interactions to translate their relatively β values into bulk large electro-optic activities. The electro-optic coefficient of poled films containing 25 wt % of these new chromophores doped in amorphous polycarbonate afforded values of 163, 129, 183 and 196 pm V−1 at 1310 nm for chromophores y1-y4 respectively. These results indicated that introducing rigid isolation group to control the shape of chromophores can efficiently reduce intermolecular electrostatic interactions, thus enhancing the macroscopic electro-optic activity. These properties, together with good solubility, suggest the potential use of these chromophores as advanced material devices.

Novel chromophores with excellent electro-optic activity based on double-donor chromophores by optimizing thiophene bridges

Three novel nonlinear optical chromophores based on the same bis(N,N-diethyl)aniline donor have been synthesized and systematically characterized. These chromophores showed good thermal stability and chromophore y1 showed the best thermal stability of 249 °C. Besides, compared with the chromophore (y1) without the substituted group, chromophores y2 and y3 show better intramolecular charge-transfer absorption. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic coefficients. The electro-optic coefficient of poled films containing 25% wt of chromophores y1–y3 doped in amorphous polycarbonate afforded values of 149, 138 and 157 pm/V at 1310 nm for chromophores y1–y3 respectively. These results indicated that the double donors of bis(N,N-diethyl)aniline unit can efficiently improve the electron-donating ability and the special structure can reduce intermolecular electrostatic interactions, thus enhancing the macroscopic electro-optic activity. These properties, together with good solubility, suggest the potential use of these chromophores as advanced materials.

Nonlinear optical chromophores based on Dewar's rules: enhancement of electro-optic activity by introducing heteroatoms into the donor or bridge.

In this work, we investigated the enhancement of the electro-optic response by introducing electron-rich heteroatoms as additional donors into the donor or bridge of a conventional second-order nonlinear optical chromophore. A series of chromophores C2-C4 based on the same tricyanofuran acceptor (TCF) but with different heteroatoms in the alkylamino phenyl donor (C2 or C3) or thiophene bridge (C4) have been synthesized and systematically investigated. Density functional theory calculations suggested that chromophores C2-C4 had a smaller energy gap and larger first-order hyperpolarizability (β) than traditional chromophore C1 due to the additional heteroatoms. Single crystal structure analyses and optimized configurations indicate that the rationally introduced heteroatom group would bring larger β and weaker intermolecular interactions which were beneficial for translating molecular β into macro-electro-optic activity in electric field poled films. The electro-optic coefficient of poled films containing 25 wt% of these new chromophores doped in amorphous poly-carbonate afforded values of 83 and 91 pm V(-1) at 1310 nm for chromophores C3 and C4, respectively, which are two times higher than that of the traditional chromophore C1 (39 pm V(-1)). High r33 values indicated that introducing heteroatoms to the donor and bridge of a conventional molecular structure can efficiently improve the electron-donating ability, which improves the β. The long-chain on the donor or bridge part, acting as the isolation group, may reduce inter-molecular electrostatic interactions, thus enhancing the macroscopic EO activity. These results, together with good solubility and compatibility with the polymer, show the new chromophore's potential application in electro-optic devices.

Synthesis and optical nonlinear property of NLO chromophores with alkoxy chains of different lengths using 8-hydroxy-1,1,7,7-tetramethyl-formyljulolidine as donor

Three chromophores ZR1, ZR2 and ZR3 based on the electron donor bearing different lengths of alkoxy chains, the same π-electron bridge and tricyanofuran acceptor, have been synthesized and systematically investigated. Density Functional Theory calculations and cyclic voltammetry measurements suggested that ZR2 (with hexyloxy) and ZR3 (with octoxy) had relatively small energy gaps between ground state and excited state than ZR1 (with butoxy) due to the auxiliary electron-donating ability and steric hindrance of their longer alkoxy chains on the donor. The electro-optic coefficient of poled films containing 20% wt of the new dyes doped in amorphous polycarbonate afforded values of 48, 62 and 65 pm/V at 1310 nm for ZR1, ZR2 and ZR3 respectively. These results indicated that the introduction of the longer alkoxy chains on the donor could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores. This conclusion is conducive to future molecular design.

The electro-optic effect in P(VF2) and P(VF2/VF3) copolymer

The effective electro-optic coefficients of poled films of P(VF2) and P(VF2/VF3) have been measured using a Michelson interferometer. The interferometer allows direct measurement of electrically-induced changes in the optical path length in the films, for light of differing polarisations. In the measurements reported here, the films are unconstrained. The changes in optical path length thus arise not only from the primary electro-optic effect, but also contain photo-elastic and piezoelectric contributions.