Control of volume holograms

Received May 9, 1991; revised manuscript received February 14, 1992; accepted February 25, 1992 The mismatch in the number of degrees of freedom supported by volume holograms and the boundary fields that control them limits the dynamic range of recorded holograms. For holograms controlled by using fractal sampling grids, the maximum dynamic range falls inversely with the minimum number of exposures needed to record the hologram, the rank of the hologram. In adaptive holography, feedback between coupled holograms prevents the dynamic range from decreasing faster than the fundamental limit. If the control problem is overcome, the maximum dynamic range that a hologram can support falls inversely with the square root of the rank. In principle, holograms in which the dynamic range falls inversely with the square root of the rank can be recorded by using cross-spectrally coherent polychromatic pulses.