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

In previous work the X((3)) nonlinear optical behaviour of blue, therm ally 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 no t identical, techniques are used to determine the nonlinear response o f 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 so me reported values for red spun P4BCMU firms but significantly less th an for the blue form P4BCMU films. The results rule out the need for h igher order terms in the polarization expansion for this P9BCMU film u p to an irradiance of at least 6 GW cm(-2). The nonlinearity is shown to be genuinely of electronic origin.