THE INTENSITY-DEPENDENT REFRACTIVE-INDEX OF CHEMICALLY ENHANCED BACTERIORHODOPSIN

The intensity-dependent refractive index of a chemically enhanced bact eriorhodopsin film is shown to be composed of two components. The firs t arises from the shift in absorption band accompanying the bR-->M pho totransformation and follows the predictions made by the Kramers-Kroni g transformation. An additional modulation is observed at high laser i ntensities and is the likely result of a thermal lensing effect induce d by laser heating. This study provides for the first time new insight and quantitative descriptions of the regimes of the refractive index modulation in bacteriorhodopsin and is helpful in understanding the po tential use of the BR refractive index modulation in optical applicati ons.