Demonstration of a continuous scanner and time-integrating correlator using spatial–spectral holography

We present a new approach to time-integrating correlation using spatial–spectral holography in which an optically modulated temporal input is spatially scanned by diffracting it from an appropriately programed spatial–spectral grating. The grating required for this scanning operation is programed into the inhomogeneously broadened medium by interfering the image of the traveling-wave diffracted light from an acousto-optic deflector (AOD) with the temporally modulated light from an acousto-optic modulator, thereby recording a spatial–spectral holographic copy of the traveling-wave scanning characteristics of the AOD. This scrolling diffracted field is interfered with a temporally modulated correlation reference and accumulated on a 1-D CCD photodetector array, and is thus quite analogous to an acousto-optic time-integrating correlator (TIC), but without the inherent bandwidth limits of acoustic-wave propagation. This spatial–spectral holographic TIC is experimentally demonstrated at bandwidths of about 30 MHz with 150 resolvable spots and 10 ms of coherent integration time, and the prospect for much wider bandwidth, longer integration time, larger processing gain, and higher resolution are explored.