Intracavity Absorption Spectroscopy of Atmospheric Water Vapor Using a Multimode Traveling-Wave Ring Dye Laser

The intracavity absorption spectra of water vapor in the atmosphere were observed in situ using a multimode unidirectional traveling-wave ring dye laser. Water vapor lines with absolute absorption coefficients of 10-7 to 10-9 cm-1 were measured with uncertainties of a few percents and their values were consistent with those in the HITRAN database within 10%. The sensitivity of the present apparatus was estimated to be 1 ×10-10 cm-1.