ALL-OPTICAL NONLINEAR HOLOGRAPHIC CORRELATION USING BACTERIORHODOPSINFILMS

Films made of the halobacterial photochrome bacteriorhodopsin (BR) can be used in a number of holographic real-time applications. Their appl ication as active material in a dual-axis joint-fourier-transform (DAJ FT) real-time correlator was shown recently. The BR films have a stron g nonlinear intensity dependence on the light-induced absorption and r efractive-index changes. Therefore the holographic diffraction efficie ncy also shows a nonlinear dependence on the writing intensity. We inv estigate the effect of this nonlinearity on the result of the correlat ion process in a bacteriorhodopsin-based DAJFT correlator. Numerical m odels supporting the experimental observations are presented. It was f ound that the BR film combines the holographic function for most objec ts with that of a spatial bandpass filter, whose center frequency is t uned by the writing intensity. This results in smaller peak widths and a suppression of the sidelobes. BR films allow the application of thi s nonlinear behavior in real time to the all-optical correlation proce ss.