It is well known that an appropriate apodization of the light beam within acousto-optical data processing makes it
possible to increase the potential dynamic range of a system up to 40 dB and more. Customary, the Gaussian
apodization is used when a light beam incidents on a rectangular uniform operative aperture of acousto-optical cell.
However, modern acousto-optics exploits often rather high-frequency radio-wave signals in a view of increasing the
frequency bandwidth by itself or/and growing the time-bandwidth product inherent in a cell. Anyway, similar acoustooptical
cells operate with such frequencies that acoustic losses become already pronounced, so that the effect of these
losses along an aperture of a cell has to be taken into account. Typically, acceptable level of the acoustic losses accounts
about 3 − 6 dB per cell’s aperture. By this it means that the expected no-uniformity of distributing the acoustic energy is
now not negligible. To obtain really optimized profile of the incident light beam apodization the expected influence of
acoustic losses ought to be analyzed and estimated. In connection with aforementioned no-uniformity or asymmetry, one
can propose exploiting a quasi-Gaussian profile of the incident light beam reasonably shifted relative to the center of an
aperture of the acousto-optical cell with appreciable acoustic losses.
This processor is oriented to studies in the extra-galactic astronomy as well as to searching the extra-solar planets, so that algorithm of the space-and-time integrating is desirable for a wideband spectrum analysis with an improved resolution. It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z − transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of designing the triple product acousto-optical processor in frames of the astrophysical instrumentation is presented.
Basic performances of the acousto-optical cells, which can be potentially involved into creating a novel triple-product acousto-optical processor for modern astrophysical applications, are under estimation. The main attention is paid to the time-bandwidth product, because just this parameter can be taken as the most general one for the characterization of performance data inherent in each individual cell. Functional capabilities peculiar to the cells operating over either normal or anomalous light scattering regime are under consideration. Evidently, the anomalous regime of light scattering promises better results. Both the theoretical estimations and the experimental data obtained for a large-aperture acousto-optical cell based on a tellurium dioxide crystal, exploiting the anomalous light scattering, gives the time-bandwidth product equal to about 4000 .
Rather specific types of light diffraction in the condensed matters are analyzed theoretically, so that in fact a set of
processes conditioned by a multi-phonon light scattering in the Bragg regime is under investigation. Besides of their
scientific novelty, studying these phenomena promises real progress in applications, because practical exploiting of the
m - phonon processes in frontier schemes for the acousto-optical spectrum analysis of both optical and radio-signals
leads potentially to improving the frequency and/or spectral resolution of the corresponding analyzers by almost
m - times. With this in mind, the wave-based description, the corpuscular approach as well as the quantum
interpretation of acousto-optical interaction are used here to characterize various aspects related to improving the
expected resolution of acousto-optical devices exploiting a multi-phonon light scattering. In so doing, the quantity of
orders under consideration is limited by number N ≤ 4 , which is still hopefully possible to be achieved experimentally
in Bragg regime. Additionally, a brief description of a multi-order light scattering by usual thin diffraction grating is
presented in the appendix for the convenience of its physical comparison with the results obtained for acousto-optics.
Both a high level of developing the spatially spot-like and one-dimensional input devices and the flexibility of a design
inherent in two-dimensional optical systems with similar modulating components make it possible to realize various
high-bit-rate opto-electronic processors. This is why a one-dimension acousto-optic technique has been involved in data
processing and its modeling based on the algorithm of triple product correlations. Practically, triple product correlations
originate within an optical scheme including the modulated light source, representing the first input port, and two wideaperture
acousto-optical cells forming two other input ports. Due to specifically constructed lens system, initially
modulated light beam is crossing sequentially the apertures of acousto-optical cells oriented at right angle to each other.
Finally, a CCD-matrix integrates the received optical signal with respect to time and registers the resulting triple product
correlations. In a view of arranging similar acousto-optical processor for modeling triple product correlations, we
characterize a novel version of the acousto-optical cells exploiting now tellurium-dioxide crystals. Together with this,
potential performances of the progressed design for similar processor are estimated as well.
Some practical aspects of creating an acousto-optical processor oriented to the calculation of triple auto- and cross-correlations
of low-power short optical pulses in time domain are under preliminary consideration. In so doing, the
shapes of both the triple auto-correlations and the bispectra inherent in the most commonly used pulses are
mathematically expressed and numerically illustrated, and the needed general schematic arrangement for a triple
correlation acousto-optical processor is designed and briefly discussed. Then, in a view of exploiting the one-channel
wide-aperture acousto-optical cells within operating similar processor, the performances of lead-molybdate crystalline
cells are tentatively estimated.
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