THE ELECTRONIC NONLINEAR-OPTICAL BEHAVIOR OF A GRATING-COUPLED POLYMER 9BCMU WAVE-GUIDE

In previous work the X((3)) nonlinear optical behaviour of blue, thermally evaporated P4BCMU has been investigated at a wavelength of 1.064 mu m using grating coupled waveguide techniques. The measured response was shown to be electronic in origin. In this work similar, though not identical, techniques are used to determine the nonlinear response of a related polymer, PSBCMU. The results show an irradiance-dependent refractive index X((3)) value (Re(X((3))) = -4.4 x 10(-11) esu (2.0 x 10(-19) m(2) V-2); Im(X((3))) = 4.4 x 10(-11) esu) much higher than some reported values for red spun P4BCMU firms but significantly less than for the blue form P4BCMU films. The results rule out the need for higher order terms in the polarization expansion for this P9BCMU film up to an irradiance of at least 6 GW cm(-2). The nonlinearity is shown to be genuinely of electronic origin.