Nonlinear optical properties of high glass-transition temperature polyphosphazene films

Polyphosphazenes with high glass-transition temperatures have been prepared according to a newly developed synthetic route. The 4-[(4'-nitrophmyl)azo] phenoxy chromophore has been incorporated as a side-chain group in a concen tration around 30% by weight. The nonlinear optical (NLO) properties of pol yphosphazene films have been studied. The three components of the second-or der NLO susceptibility tensor for corona poled films are chi ((2))(15) = 9. 3 x 10(-24) C/V-2 (2.5 x 10(-9) esu), chi ((2))(31) = 9.6 x 10(-24) C/V-2 ( 2.6 x 10(-9) esu) and chi ((2))(33) = 28.2 x 10(-24) C/V-2 (7.6 x 10(-9) es u) for a poling field of 6 kV and a temperature of 140 degreesC. The Kleinm an symmetry and the condition chi ((2))(33) = 3 chi ((2))(31) are approxima tely obeyed within the experimental error. At room temperature (RT), the th ermal stability of the second-order NLO response is very high since the chi ((2))(15) value decreases by less than 10% in 70 days. The third-order NLO susceptibility has also been determined and reaches 0.38 x 10(-31) C m/V-3 (0.31 x 10(-12) esu) for the unsubstituted polymer and 3.2 x 10(-31) C m/V -3 (2.6 x 10(-12) esu) for the substituted (side-chain) one. (C) 2000 Elsev ier Science S.A. All rights reserved.