NONLINEAR REFRACTIVE-INDEX CHANGE OF PHOTOACTIVE YELLOW PROTEIN

The nonlinear refractive index change of photoactive yellow protein (P YP) was examined by measuring the shape of an originally Gaussian-shap ed laser beam after it had propagated through a PYP-film. An unique re shaping of the beam profile was observed. By this data the nonlinear p art of the refractive index was calculated by applying optical map tra nsformation. The result was verified by reconstructing the far-field p attern of the beam with the calculated nonlinear refractive index and the Rayleigh-Sommerfeld diffraction formula. The results show that PYP exhibits much stronger nonlinearity than Kerr-Like materials. (C) 199 8 Elsevier Science B.V. All rights reserved.