Simultaneous measurements of complex birefringence in azo dye doped polymer films induced by linearly polarized light

Abstract

A complex birefringence originating in a photoinduced alignment of azo dye (4-[ N-(2-hydroxyethyl- N-ethyl]amino--nitroazobenzene (disperse red 1)) molecules in the polymer matrix poly(methyl methacrylate) (PMMA) was determined with a Mach-Zehnder interferometric method. The complex birefringence was proportional to the intensity of the pump beam. The absolute value of the imaginary part was about half as large as the real part, although the imaginary part of the linear refractive index is negligibly small. The result suggested that the contributions of the real and imaginary parts of the complex birefringence should be observed separately even in the off-resonant case.