Micrometer-Sized Sensors with Free-Space Optical Energy Harvesting in CMOS

Abstract

This paper presents sensor nodes based on optical energy harvesting implemented in commercial CMOS processes. The chips use a photodiode to harvest the optical energy provided through a visible laser directly into a DC power line. This eliminates the need for an analog circuit chain to regulate the harvested power, thereby significantly decreasing chip area. The harvested power is then fed into a digital circuit and an output amplifier. These two parts are multiplexed in time to ensure the most efficient use of the harvested power. The digital circuit converts an 8-bit parallel code into serial and feeds it into the transmitter. The active areas of the implemented chips are 300x60 μm2 and 150x30 μm2.