Silicon Microphotonics

A rebuilding of the world’s information infrastructure is taking place to give instantaneous availability of data, voice and video. This revolution of the Information Age is being gated more by the introduction of new materials and components, than by the design of systems, software and networks. Electrons transmitted through metal wires have an information carrying capacity limited by the resistance and capacitance of the cable and the terminating electronic circuits. Photons transmitted through fiber are capacity limited only by the dispersion of the medium. Each network node that requires transduction from photonics to electronics limits the performance and affordability of the network. The key frontier is the large scale integration and manufacturing of photonic components to enable the distribution of high bit rate optical streams to the individual information appliance. Microphotonics is the platform for large scale, planar integration of optical signal processing capability. INTRODUCTION It is now one-half century since the advent of solid state electronics with the invention of the transistor. Through unparalleled gains in functionality at relatively constant cost, integrated circuits have enabled telecommunications, computation and manufacturing to move to the leading edge of societal change. This revolution has been conducted with “the turn of a single knob”: the shrinking of device dimensions. During the last two decades a new “killer technology” has emerged in the telecommunications field. This photonic technology uses optical fibers for interconnection, and has delivered an exponential increase with time of information carrying capacity to the industry. Photonics has provided unparalleled bandwidth to the backbone of the discrete, point-to-point long distance (Wide Area Network) telephone line technology. However, the circuit architecture (central switching office) that worked so well for voice communications now limits the universal access that is required for Internet and data communications. A single optical fiber, with several hundred gigabits/second of capacity, is limited by electronic processing at each circuit node. To avoid this problem optical signal processors are required: e.g., optical cross-connects and optical add/drop multiplexers. To provide full functionality, these components must be integrated at densities compatible with microelectronic integration. This microphotonics platform represents not only a solution to information access, but it can also solve the problems of bandwidth, pin-out density, reliability and complexity that threaten to end the advance of the silicon integrated circuit technology. A good figure of merit for the performance of microphotonic integrated circuits is (speed)/(power)x(area). The Information Age was ushered into existence by Microelectronics. The future will depend on the networking of databases for universal accessibility. This new Age of Connectivity will require a mating of microelectronic and fiber optic technology through integrated of Microphotonic functionality.