Abstract

We have observed some of the absorption lines from the molecules ¹²CO₂ and ¹³CO₂ in the 1.6-μm spectral region with the use of specially fabricated single-mode InGaAsP distributed-feedback semiconductor diode lasers. Using a 23.6-m-long multipass absorption cell in combination with radio-frequency modulation and detection techniques, we measured the ¹²CO₂:¹³CO₂ isotopic ratio of two specific lines at 6253.73 and 6253.90 cm⁻¹ with sufficient precision for diagnostic medical tests that analyze CO₂ on human breath.

© 1993 Optical Society of America

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