Long-Range, mm-Scale Wireless Optical Power Delivery Using Nanophotonic Antennas and Integrated Power Management

Dartmouth College, Hanover NH

Investigators

Abstract

The need for wireless power delivery has grown in recent decades, driven by exponential (Moore's law) semiconductor scaling, the pervasiveness of portable computing and communications devices, and other applications including biomedical devices, transportation and aerospace. This project will explore delivering power to small (mm-scale) silicon integrated circuits via a free-space optical (near-IR laser) power source. The goal of the project is to study and demonstrate the feasibility of long-range optical power delivery in a silicon platform through an interdisciplinary effort on semiconductor optics/photonics and low power integrated circuit design. This project will focus primarily on the optical receiver technology including the design and fabrication of nanophotonic antennas to concentrate energy into small silicon-based photovoltaic cells that are implemented in a low-cost standard process flow. The circuits portion of the project will explore methods to extract maximum energy from the optical elements and provide a seamless interface between on-chip dielectric energy storage and a low-voltage embedded circuit load. This project will support educational opportunities in the undergraduate and graduate curriculum at Dartmouth, as well as an expansion of ongoing K-12 outreach programs and communication with the general public. An example of this is the Dartmouth-organized 'Design-it, Build-it' summer bootcamp for high school juniors and seniors that attracts students from around the country and encourages students with underrepresented backgrounds to attend through the provision of scholarship support. This project will explore several promising technical directions related to mm-scale optical power delivery. A first direction is the design and implementation of near-IR (~850 nm) nanophotonic antenna structures, which can concentrate optical power to small photodiodes (PDs) operated in photovoltaic (PV) mode. These have the advantage of concentrating optical energy into very small optically-active structures, which can improve quantum efficiency and reduce active area needed for optoelectronics, thereby decreasing overall size. Second, we will explore integration strategies in SOI or triple-well CMOS where multiple photodiodes can be dynamically reconfigured in parallel and series stacks. This will help alleviate stress on the power circuitry, enable much higher system efficiency, and benefit from recent developments in power management for photovoltaic (PV) systems. Third, we plan to develop a novel power management approach based on high-density switched capacitor (SC) converters that can provide efficient regulation and power-point tracking with a monolithic implementation while interfacing between high-voltage dielectric storage and a low-voltage embedded system load. The proposed SC architecture builds on past work by the PIs in chip-scale power conversion, architectures that can to mitigate systemic energy loss mechanisms in photovoltaic arrays, and new directions in high-order interleaving and bottom plate recycling that can improve efficiency and power-density.