Photonic Device Design from the Complex Plane to the Microprocessor: Keeping Information, Energy and Entropy Under Control

Four decades from its pioneering first steps at Bell Labs, microphotonics is transitioning from a few components to large-scale integrated systems on chip. In the near term, this can address severe bottlenecks seen in complex digital electronic systems – through integration with relatively simple but efficient photonic systems. In the longer term, tight integration and control mean complex passive, active, and nonlinear photonic structures enabling novel functions will become practical and may enable a new generation of integrated systems-on-chip for analog signal processing, computation, metrology, sand sensing.

I will first describe work that bucked the trend of tailoring fabrication to design, instead pursuing a "design for manufacture" philosophy to photonic device innovation within fixed advanced-node CMOS microelectronics technology. This work enabled millions of transistors and thousands of photonic devices to coexist side-by-side for the first time, produced efficient electronic-photonic systems (including record-energy optical transmitters, receivers, and links), and resulted in the demonstration of the first microprocessor that communicates using light, with significant implications for computer architecture.

The second part will cover example complex photonic device concepts that expose and address fundamental challenges and apparent limitations in optical signal processing. I will talk about the fundamental limits of modulators and breaking their speed-energy tradeoff, as well as about the "entropy pump," a nonlinear photonic device designed to passively manipulate the coherence of light, and, for example, denoise laser light with high efficiency. With complex integration enabling control, such complex or sensitive photonic "circuits" could enable a new level of capabilities for a next generation of optical signal processors.

Speaker: Milos Popovic, Univ. of Colorado