Abstract

A modified dual-axis joint-Fourier-transform correlator with two liquid crystal spatial light modulators as input devices and a bacteriorhodopsin film as holographic recording material in the Fourier plane is capable of processing two independent video signals at a TV frame rate with a signal-to-noise (S/N) ratio of 45 dB. The polarization recording properties of the bacteriorhodopsin films allow the effective suppression of, e.g., scattered light from the correlation signal, which leads to the high S/N ratio. The use of mutated forms of bacteriorhodopsin (BR), which are obtained by genetechnological modification of this biological photochrome, supplies materials with improved light sensitivity and/or a spectral range that allows the use of compact solid state lasers. The dense packing of the BR chromophores in a twodimensional crystalline lattice, the so-called purple membrane (PM), causes the excellent thermodynamic and photophysical stability of PM and facilitates the preparation of BR films with a thickness down to 10 µm but high initial optical densities of up to OD(570 nm) = 10. These films have a spatial resolution of about 5000 lines/mm and holographic diffraction efficiencies up to 7%.

© 1992 Optical Society of America