The intensity-dependent refractive index of a chemically enhanced bacteriorhodopsin film is shown to be composed of two components. The first arises from the shift in absorption band accompanying the bR→M phototransformation and follows the predictions made by the Kramers-Kronig transformation. An additional modulation is observed at high laser intensities and is the likely result of a thermal lensing effect induced 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 potential use of the BR refractive index modulation in optical applications.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry
- Electrical and Electronic Engineering