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Two-dimensional arrays of mutually coherent optical beams are needed in holographic interconnections for both recording and reading gratings. We analyze the use and limitations of binary phase Fresnel lenses to generate beams for these applications. Two known techniques of ion beam milling and thin film deposition are compared to fabricate such lens arrays in SiO(2) and Si(3)N(4). Each lens in the 8 x 8 arrays has a 1.2-mm square aperture with a focal length of 20 mm. Diffraction of a single argon-ion beam into an 8 x 8 array of highly uniform coherent focused beams (with 12-microm spot size) was achieved by the lenses with an efficiency of approximately 30% (41% theoretical limit).

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The energy transfer between two beams (signal and reference, respectively) writing a dynamic-volume hologram in photorefractive BSO crystals is applied to the image amplification of a diffuse object. The image intensity transmitted by the crystal is amplified 10x in the presence of the pump reference beam. The crystal is used in the drift recording mode (applied electric field, E(0) = 10 kV cm(-1); fringe spacing, Lambda = 3 microm), and beam coupling is induced by the nonlocal response of the crystal that is due to the fringe displacement at a constant speed. We have applied this two-wave mixing configuration to a real-time optical-processing operation; the related energy transfer and stationary image amplification permit the mode pattern visualization of a vibrating structure.

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