Thiophene based Nonlinear Optical Chromophore functionalized Epoxy Polymers for Electro-Optic Applications

Abstract

Polymeric materials present certain advantages over inorganic crystals for second-order nonlinear optical (NLO) applications because of their low dielectric constant, large optical nonlinearity, low cost, and ease of processability. Stable NLO polymeric materials are potential candidates for electro-optic (EO) devices such as high bandwidth electro-optic modulators [1], optical interconnects [2], and fiber optic gyros [3]. Second-order NLO properties in polymers are present when the chromophores are aligned in a non-centrosymmetric manner. Chromophores with enhanced NLO susceptibilities can be obtained by increasing electron-donating and/or accepting effects [4], by extending the conjugation length between the donor and acceptor groups [5] and by replacing the phenyl moieties in the chromophores with thiophene moieties [6]. Efforts were made by our group [7] and various other groups [6, 8] to synthesize and optimize the properties of the chromophore functionalized polymers with high optical nonlinearity. Jen and coworkers synthesized a variety of thiophene based chromophores with high optical nonlinearity, 'μβ' [6, 8]. Many of these chromophores, when doped in a polymer matrix exhibited an electro-optic value greater than 20 pm/V. Marder and coworkers studied the effect of strong acceptors in NLO chromophores and have found that an 'r33' value of 55 pm/V at 1.313 μm is realizable with some of these chromophore doped polycarbonate composites. However, most of these systems are of guest-host type, which limit the chromophore solubility as well as temporal stability of the poled order in the NLO chromophore-polymer composites.