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A new architecture for photorefractive adaptive filtering is introduced. This architecture is based on the principle of time-integrating correlator with a photorefractive material as the time-integrating photosensor. A compact and rugged system is achieved by using the same Bragg cell as both the delay line for computing correlation values and the delay to which the tap weights are applied. In this way a self-aligning structure is achieved. Semiconductor photorefractive materials are used with 1.2-1.3-microm wavelength injection lasers to achieve fast response, low power, and a compact structure. Tests of an experimental system demonstrated >40-dB rejection of narrow-band interference with a transient response time constant of 70micros.

The effect of temperature, atmosphere, and elemental concentrations of boron and phosphorous in ferrous alloys on the wettability of polycrystalline α‐Al2O3 was studied. The investigation of the wetting behavior is of major importance to the infiltration of steel into open foam ceramics. In reference Fe‐0.46 wt% C iron samples, the contact angle was investigated between 1550 and 1650 °C under Ar‐H2 and Ar atmospheres and was found to decrease with increasing temperature and increasing oxygen partial pressure. Furthermore, no FeAl2O4 (hercynite) spinel type inclusions were found in Fe/Al2O3 experiments. In the Fe‐P binary alloys, θ decreased with increasing phosphorous content and was ≈112° for the Fe‐0.299 wt% P alloy at 1600 °C. For the Fe‐B binary alloys, a strong influence of boron on the contact angle was found. Secondary neutral mass spectrometry (SNMS) analysis showed a maximum in the boron concentration in the first 50 nm of the metallic side of the interface. In the FeCrMnNi‐P high‐alloys specimens, a reaction layer was found between the steel/ceramic interfaces. The contact angle was ca. 90°, lower than the Fe‐P binary alloys.

The fast shear acoustic modc in Gallium Phosphide, with acoustic propagation in the [ I .-1.01 direction and pcrlari7ation in the [0.0,1 J direction, is particularly attractive for acousto-optic applications because of its anisotropic acoustic "self-collimating" beam property. The orthogonally polari7cd slow shear mode, however, has a similar acoustic velocity (3.09 vs. 4.13 m m / p for the self-collimating mode) and figurc of merit, M2, (4.3 vs. 16.5 for the self-collimating modc). Excitation of this orthogonal mode will lead to unwanted acousto-optic diffraction and subsequent reduction in h e spurious free dynamic range of the acousto-optic device. Both transduccr selection and orientation with respect to the acousto-optic crystal are critical in suppressing the unwanted slow shear mode. An optimum Lithium Niobate transducer cut is described and thc slow shear mode suppression is calculatcd as a function of trancducer misorientation. An alternative optical propagation direction is also examined where the coupling to the slow shear mode vanishes at thc expense of increased accruetic hcam divcrgcnce. The negative phase front curvature of this modc is discussed.