Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis

Broad-bandwidth, high-spectral-resolution optical detection of human breath has identified multiple important biomarkers correlated with specific diseases and metabolic processes. This optical-frequency-comb-based breath analysis system comes with excellent performance in all criteria: high detection sensitivity, ability to identify and distinguish a large number of analytes, and simultaneous, real-time information processing. We demonstrate a minimum detectable absorption of 8 x 10(-10) cm(-1), a spectral resolution of 800 MHz, and 200 nm of spectral coverage from 1.5 to 1.7 mu m where strong and unique molecular fingerprints exist for many biomarkers. We present a series of breath measurements including stable isotope ratios of CO2, breath concentrations of CO, and the presence of trace concentrations of NH3 in high concentrations of H2O. (C) 2008 Optical Society of America.