Alignment and assembly of diffractive optical elements for optical system packaging

Abstract

Free-space optical interconnects for microelectronics and multiprocessor parallel computing systems offer better scalability because less silicon area will be occupied by interconnections and they have a faster clock speed and higher bandwidth at power levels than do purely electronic systems. For stability and ruggedness optoelectronic systems that combine optics with electronics based on free space optical interconnection need to be packaged. In packaging these types of systems, diffractive optical elements (DOEs) are often used because their fabrication is compatible with VLSI fabrication and they can be flexibly designed by computer. The volume of the packaged system depends on the f-number of the DOE utilized in the system: the smaller the f-number, the more compact the packaged system. Lower f- number DOEs can be obtained by stacking more than one DOE together. Stacking also helps to achieve larger diffraction angles to facilitate longer distance interconnects. The problems to be solved are (a) accurate alignment between DOEs on the opposite sides of one substrate or between DOEs on separate substrates and (b) bonding or assembly of separate substrates. In this presentation, the alignment and assembly procedures for stacking more than one DOE together will be discussed, and the experimental results shown.