Monolithic CMOS-Compatible CO2 Sensor with Thermal Source and Detector

We present a novel monolithic photonic sensor for carbon dioxide (CO
2
) detection in the mid-infrared (mid-IR) at 4.26 μm wavelength, based on Si waveguides and developed on a Si platform. The sensor consists of two units, each with a size of less than 2 mm
³
and comprising a thermal emitter, a waveguide, a spectral filter and a detector. All sensor elements are CMOS compatible and were fabricated on the same chip using standard mass-fabrication processes. To the best of our knowledge, this is the first report of a monolithic CO
2
photonic sensor in the mid-IR based on evanescent-wave absorption and utilizing exclusively thermal sources and detectors. Although the achieved detection limit is currently about 5% CO
2
, further optimization of the sensor elements can significantly decrease this value. This sensor represents a significant step forward towards developing inexpensive miniaturized sensors for the consumer market.