Chromophores with Strong Heterocyclic Acceptors: A Poled Polymer with a Large Electro-Optic Coefficient

Abstract

Syntheses of a series of conjugated donor-acceptor chromophores, based on a strongly electron-withdrawing heterocyclic acceptor, have led to compounds with large second-order optical nonlinearities. Incorporation of one of these chromophores into polycarbonate at 20 percent weight loading yielded, after poling at 150 volts per micrometer, a polymer film with an electro-optic coefficient, r 33 , of 55 picometers per volt at 1.313 micrometers. This value is roughly twice that of lithium niobate. A variant of one of these chromophores exhibited improved thermal stability as needed for use in polymers with higher glass transition temperatures. The chromophore was soluble in common organic solvents, had a scalar product of the dipole moment, μ, and the molecular first hyperpolarizability, β (corrected for dispersion), of roughly 5000 × 10 −48 electrostatic units, and showed less than 10 percent decomposition after heating for 20 minutes in air and at 200°C in an inert organic solvent.

The role of London forces in defining noncentrosymmetric order of high dipole moment–high hyperpolarizability chromophores in electrically poled polymeric thin films

“…Of these methods, electric field poling is the protocol most easily applied to a wide range of chromophores and poling has been the most commonly used materials processing approach for fabrication of prototype devices utilizing organic nonlinear optical materials. To date, electric field poling has yielded materials with optical nonlinearities in the range of 20-55 pm͞V (11,(18)(19)(20) which is substantially below the values expected if chromophore-chromophore electro-static interactions are neglected and electro-optic coefficients are predicted to scale as ␤͞MW, where is the chromophore dipole moment, ␤ is the first molecular hyperpolarizability, and MW is the chromophore molecular weight.…”

“…Of these methods, electric field poling is the protocol most easily applied to a wide range of chromophores and poling has been the most commonly used materials processing approach for fabrication of prototype devices utilizing organic nonlinear optical materials. To date, electric field poling has yielded materials with optical nonlinearities in the range of 20-55 pm͞V (11,(18)(19)(20) which is substantially below the values expected if chromophore-chromophore electro-static interactions are neglected and electro-optic coefficients are predicted to scale as ␤͞MW, where is the chromophore dipole moment, ␤ is the first molecular hyperpolarizability, and MW is the chromophore molecular weight.The neglect of chromophore-chromophore electrostatic interactions, although widely used in discussing putative scaling of microscopic to macroscopic optical nonlinearity (21-23), has not been justified. Indeed, it is more reasonable, in general, to assume that noncentrosymmetric order (and hence, electro-optic and second harmonic generation coefficients) will be determined by the competition of ordering and disordering electrostatic forces.…”

Nonlinear optical properties of push–pull polyenes for electro-optics

“…[1][2][3][4] Compared with the de facto standards disperse red and diamino nitro stilbene, the relevant nonlinear parameter ␤(Ϫ; , 0) is increased by up to more than 20-fold. Therefore the novel chromophores have the potential to increase the electro-optic (EO) coefficient of polymeric materials much above the present level of 30 pm/V found in state-of-the-art devices (either polymers or inorganic materials like LiNbO 3 ) at the wavelength of interest (1.3 or 1.5 m).…”

Development of Highly Active Electro-Optic Polymers for In-Line Fiber Photonic Devices

“…In order to demonstrate the potential of organic materials, we present a comparison of a very well know and widely used NLO chromophore, DR1 (chromophore 1), with a recently developed chromophore for EO polymers (chromophore 2) [17]. Table 2 lists the relevant properties.…”