Photoinduced Nonlinear Refraction In A Polymeric Film Encapsulating A Bacteriorhodopsin Mutant

The absorption change versus time after switching off the illumination on a polymeric film that contained a bacteriorhodopsin (BR) mutant has been measured. The M-lifetime of this BR mutant is similar to 320 s. A pertinent Z-scan was performed to study the BR optical nonlinearity. A physical model with multi-level transitions in the Z-scan was suggested. The minimum saturated light intensity measured at 633 nm is similar to 0.9 mW/cm(2). A low intensity of 70 mu W/cm(2) has been used for recording in this film. The change in refraction index Delta n(633) is -3.0 x 10(-3) and Delta n(476) is 8.5 x 10(-3) with the intensity all at similar to 100 mW/cm(2). (C) 2010 American Institute of Physics. [doi:10.1063/1.3480410]