CORRELATION PATTERNS AND CROSS-TALK NOISE IN VOLUME HOLOGRAPHIC OPTICAL CORRELATORS

We analyze the correlation pattern and the cross-talk noise of optical correlators, using multiplexed volume holograms as matched filters. Our results show that sidelobes of the correlation patterns are suppressed in such an optical system; therefore the signal-to-noise ratio in pattern recognition is significantly higher than that in a planar holographic correlator system. We consider both angle- and wavelength-multiplexed holograms and compare the results for various thicknesses of volume holographic media. Our results show that the degree of sidelobe suppression depends on the thickness of the holographic medium and the angle between the object beam and the reference beam during recording. When the correlation patterns obtained with the transmission holograms in angle multiplexing are compared with the reflection holograms in wavelength multiplexing, it is seen that the sidelobes decrease much faster with the increase of thickness with angle multiplexing than with wavelength multiplexing. In addition, we demonstrate the effect of sidelobe suppression, and our experimental result is in good qualitative agreement with theoretical predictions.