The intensity dependent refractive index change of bacteriorhodopsin measured by the Z-scan and phase-modulated beams techniques

Abstract A comparative analysis of intensity dependent refractive index change of a thin polymer bacteriorhodopsin (bR) film by the Z -scan and phase-modulated beams techniques is given. The analysis is conducted at two excitation wavelengths, λ =543 and 633 nm, corresponding to the opposite slopes of the bR ground-state absorption band resulting in opposite signs of the refractive index change. A three-level model of the bR photo-cycle is proposed to describe the experimental data.