Intermodular products in phased array Bragg cells

A fundamental limit for the instantaneous dynamic range of acoustooptic signal processors is due to the intermodulation products (IMPs) generated in the Bragg cell when multiple signals are simultaneously present. The most important contributions to IMPs arise from multiple acoustooptic diffraction. A theoretical analysis of the multifrequency acoustooptic diffraction in phased array Bragg cells is presented. An analytical expression for the dominant IMPs is derived for two signals with finite frequency differences. The analysis explains the measured result of lower IMPs when the frequency separation is increased. By increasing the total transducer length, the minimum frequency separation for IMPs suppression is decreased. It is shown that further suppression of IMPs can be obtained by the use of apodized transducers