Acousto-optic correlation techniques

A description is given of the theory of operation of acousto-optic (AO) devices and correlators in general. Two different applications of twin Bragg cell space-integrating correlator/convolvers are then discussed. In the first a heterodyning technique is employed in which light at different optical frequencies is mixed to give the convolution of the signals applied to the two AO cells. The system is configured to implement the first two stages of the multiply-convolve-multiply algorithm so that the power spectrum of the input-signal is obtained. The second system is a novel nonheterodyning correlator/convolver. It is shown that by amplitude modulating the signals on to the Bragg cell carrier frequency using double sideband large carrier modulation, the full correlation function including amplitude and phase information, may be extracted by measuring only the intensity of light at the output of the system.<
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