Acousto-optic Time-integrating Correlator Research Articles

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.

Optical misalignment estimation in a time-integrating acousto-optic processor

An acousto-optic time-integrating correlator with center frequency 80 MHz, bandwidth 40 MHz, time aperture 10 µs, and signal bandwidth 20 MHz was designed and assembled. A novel electronic method for estimating the overall optical misalignment in the processor was devised and tested. It represents a simple and robust alternative to purely optical procedures. The resolution accuracy of the method is limited by the CCD pixel dimensions. As a side result, the scaling law that applies to the output signal when using CCD detection is also derived.

A Kosters prism time-integrating acousto-optic correlator

A double-beam acousto-optic time-integrating correlator is described that is a modification of a recently reported acousto-optic interferometer. The instrument uses a pair of Kosters double-image prisms and two tellurium dioxide Bragg cells to produce the correlation function of pulsed radio signals.

Bias-free time-integrating optical correlator using a photorefractive crystal

An acoustooptic time-integrating correlator is demonstrated using a photorefractive crystal as the time-integrating detector.

Acoustooptic matched filter correlator

The signal model used and the output SNR(0) measure chosen are shown to affect the performance of an acoustooptic time-integrating correlator. Nonuniform acoustic fields are also shown to affect the results, but these error sources can be overcome with a new hybrid time- and space-integrating acoustooptic matched filter correlator that we describe and for which initial simulation data are provided.

A new surface-wave acousto-optic time integrating correlator

A new realization of the acousto-optic time-integrating correlator has been constructed. The new device uses a surface-acoustic-wave delay line and is configured so that no separate reference beam is required for coherent detection. Instantaneous bandwidths of 30 MHz and integration times of 30 ms have been achieved. Broadband signals, such as pseudonoise biphase modulated waveforms, with signal-to-noise ratios of −40 dB have been detected. In addition, center frequency, bandwidth, and relative time-difference-of-arrival of these signals can be determined.

The distribution of impurities in silicon epitaxial films : O. Planer, Tesla Electron., April (1969), p. 117

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 30MHz with 150 resolvable spots and 10ms of coherent integration time, and the prospect for much wider bandwidth, longer integration time, larger processing gain, and higher resolution are explored.