Ginzton Laboratory, Stanford University, Stanford, CA 94305, U.S.A.
Optics dominates long distance communications, but will it ever be useful on silicon chips or their successors? In this chapter, we will discuss why we might be interested in the use of optics for such shorter interconnections, what technology we might need, and what new technological opportunities are emerging that could make such use practical or even ubiquitous.
Optics for use in handling information has been around for several decades now, with clear successes in optical fiber communications and in removable disk storage (compact discs and DVDs, for example). Early interest in optics for logic faded as integrated circuits advanced and limitations in energy for optical logic became clearer,1 but optics for communication and interconnect has become increasingly interesting. There, optics is competing against copper, not silicon. Basic issues of physics favor optics for communication anywhere a high density of information has to be communicated over any substantial distance.2,3
The physical problems and limitations of electrical wired interconnects are many and substantial. They perform increasingly poorly at higher frequencies, showing both signal attenuation and distortion. One surprising aspect of the performance is that it is essentially scale invariant: that is, once one has filled all the available space ...