Stable Second-Order Nonlinear Optical Materials Based on Interpenetrating Polymer Networks

Nonlinear optical (NLO) polymers have shown increased potential in practical applications, such as frequency doubling and electro-optic modulation, due to their large nonlinearity and ease of processing. A practical NLO polymer will need to possess large second-order nonlinearity, excellent temporal stability at elevated temperatures, and low optical loss. 1 A number of NLO polymers have been developed to exhibit large second-order NLO coefficients comparable to those of the inorganic NLO materials which are currently in use in devices.2,3 However, the major drawback of NLO polymers is the decay of their electric field induced second-order optical nonlinearities. This decay is a result of the relaxation of the NLO chromophores from the induced noncentrosymmetric alignment to a random configuration. Numerous efforts have been made to minimize this decay through different approaches.4 Recently, we have reported on an approach to stable second-order NLO polymers using an interpenetrating polymer network (IPN) structure.5,6 This IPN system, with the hybrid properties of a high glass transition temperature (Tg), an extensively crosslinked network, and permanent entanglements, exhibited excellent temporal stability at elevated temperatures.6 In this report, a new IPN system, modified from the one reported earlier,5 with higher degree of crosslinking density and larger NLO chromophore density is investigated. Electro-optic modulation, Interpenetrating polymer network, Second-order nonlinearity, Optical loss.