How will photonic integrated circuits develop?

Abstract

This paper explores issues associated with Photonic Integrated Circuit (PIC) research and development -with an overall goal of initiating a discussion of how PIC technology should develop and eventually be deployed with high impact. Significant research and development programs have focused on PICs for routing and switching, and computer interconnects. Most recently, the application domain of PICs has diversified greatly, and now includes analog signal processing, remote sensing, biological and chemical sensing, neural interfacing, and solar cells. A key feature of PIC technology growth has been the exploitation of high-density fabrication and packaging technology originally developed for the Silicon IC industry. PIC foundry services are emerging -and there has been a natural attempt to ascribe a "Moore's Law" to PIC scaling. Analogies to Silicon electronic scaling, however, should be used with caution. PIC complexity scaling may be driven more by the ability to access the degrees-of-freedom offered by PIC-based optical domain signal processing, rather than increasing device count. Specific examples of PIC research in chip-scale computer interconnects and integrated micro-concentrators for solar cells are highlighted.Much research and development has been, and is currently, focused on applying photonic integrated circuits (PICs) to chip-scale digital optical interconnects (OI) for high-density, high-throughput, computer communications [1-8] and networking [9]. In OI there is a specific goal of overcoming the performance limits of high-density metal interconnects and there has been an emphasis on developing monolithically integrated Silicon Photonic platforms to exploit the fabrication precision and device densities associated with Silicon ICs, as well as the potential for tight integration with Silicon electronic circuits. However, as evidenced by recent initiatives at the Defense Advanced Research Projects Agency (DARPA) and other sponsoring agencies, the PIC application domain may expand well beyond OI. The diverse application domain being considered for PICs now ranges from analog signal processing, to routing, to remote sensing, to biological sensing, to solar cells. This widening application domain will likely entail exploitation of a diverse set of technology platforms to match to the particular demands of processing and interfacing for each application. One can imagine a set of application-specific platforms optimized to address the particular performance requirements. One common challenge for all applications will center on engineering the interface between the PIC and optical energy that it exploits -be it for sensing, signal processing, computing, actuation, or energy transduction. Given this focus on optimizing the interface, it is anticipated that PICs will often involve hybrid integration and packaging of differing technologies. Such efforts should be able to leverage the advances made in Silicon IC packaging. Figure 1 depicts the expanding application domain of PIC technology as a pie-shaped chart. ...