InAsSb diode optical pairs for real-time carbon dioxide sensors

Efficiencies of optical pairs consisting of fast low-noise uncooled immersion LEDs and photodiodes based on InAsSb solid solution are studied. The proposed optical pairs are promising for applications in compact low-voltage sensors of carbon dioxide. The threshold sensitivity of such a sensor is several hundreds of ppm, and the measurement error is no worse than 5% in a wide range of concentrations (up to 10 v/v%) at a relatively high time resolution (50 ms) and a sample volume of no greater than 50 mL. Relatively high working rate and low volume of the sample improve diagnostics in capnography and allow applications in pediatrics and side-stream capnography including measurements of instantaneous CO$_2$ concentration in the course of breathing.