Optimization strategies for MACH: a novel electrically controllable computer-generated hologram

摘要

Abstract: The MACH (multiple, active, computer generated hologram) is a novel device combining aspects of computer generated holography with electrically controllable diffraction gratings. As such, it provides an interesting capability, falling somewhere between that of conventional fixed hologram and electrically addressed spatial light modulator (SLM) approaches to wavefront generation. Under the control of a single applied voltage, the device can selectively generate any one of a number of desired, uncorrelated optical wavefronts or wavefront transformations. Compared to the SLM, it is considerably more economical to fabricate, requires fewer supporting electronic subsystems, is more reliable and promises higher space bandwidth products. The device operating principles are outlined, showing that the ultimate performance of the MACH is, to a large extent, governed by the ability to determine the required substrate surface relief pattern. The various approaches to optimizing this highly constrained design problem are then described. These include developments of the direct search (pixel flipping) and projection algorithms. The latter in particular seem to provide an efficient way of calculating analogue, pixelated profiles, necessary for high performance MACH devices. Example results from various device optimizations are given. Following a discussion of rigorous device modeling and fabrication techniques, initial experimental results are presented, and potential applications discussed. !19