Determination of the refractive index of a bacteriorhodopsin film

The wavelength-dependent refractive index of a bacteriorhodopsin thin film is measured by the use of a modified critical-angle technique. The effect of the host bovine skin gelatin on the refractive index is analyzed. The measured data on the thin film can be useful for system applications. The methods and procedures are generally applicable to any optically absorbing thin films. Recently the biological photochrome bacteri-orhodopsin (bR) has drawn the attention of the optics community because of its large optical nonlinearity and real-time holographic recording capabilities. " To exploit bR's potential in optical system applications more fully, it is often necessary to know its exact refractive index. Although the optical properties and the applications of bR have been an active research area, to our knowledge no data on bR's refractive index are available. For an absorbing film with a good freestandin