The angular dependence of the hyper-Rayleigh scattered light intensity from
a suspension of bacteriorhodopsin has been analyzed. The observation calls
for combination of the second-order nonlinear hyperpolarizability of the r
etinal chromophore with the linear refractive index of the ape-protein matr
ix. The structuring of the small nonlinear chromophore in the large linear
matrix imparts properties of a photonic bandgap to bacteriorhodopsin. (C) 2
000 Optical Society of America.