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In recent years there has been a great deal of interest in the use of optical interconnection techniques within a digital electronic circuits. The Semiconductor Industry Association has highlighted the necessity of the optical approach in "The National Technology Roadmap for Semiconductors" in 1997 [1]. The availability of large space-bandwidth product, together with the potential inadequacies of copper, have usually been cited as the main advantages of optics over its electronic alternatives for interconnection applications. As more advanced and high density photonics devices in 2D format have been developed, the need for more advanced micro-optical components that allow the manipulation of light from, and interconnection between these arrays of devices in the third dimension, has grown with it. The rapid development of the field of diffractive optics (i.e. digital holography) and other micro-optical fabrication technologies over the past 20 years has to a major extent been motivated, and influenced by the requirements mentioned above. These elements have been able to provide solutions to problems, where conventional bulk optics offer no (elegant) solutions. They have proven to be particularly successful in providing fan-out, fan-in and optical interconnections of nonlocal and global permutations. [See ref. 1 and references therein]. The availability of more advanced fabrication technologies, similar to those in VLSI manufacturing, has allowed these surface-relief elements to become more efficient, easily reproducible and have more complex functionality. Here a number of available technologies for realising these optical interconnects will be described. I will primarily concentrate on the design, fabrication and applications of surface relief structures as well as refractive microlens arrays for use in a number of interconnection and switching systems. In addition, the role and advantages offered by diffractive microstructures in precise alignment of opto-electronics device arrays with micro-optical components, that are required for beam shaping in system applications, will be discussed [2-4].
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