DIRECT OPTICAL ABSORPTION MEASUREMENTS IN GASEOUS MEDIA BY THE CAVITY RING-DOWN SPECTROSCOPY TECHNIQUE FOR THE DEVELOPMENT OF A LOSSMETER

摘要

Direct absorption optical measurements with sensitivities better than 2 ppm/cm can be made using pulsed light sources and employing a simple optical cavity configuration. This paper demonstrates that the integrated absorption signal provides a quantitative total absorption measurement if the losses of resonant cavity are not dominated by mirror losses. This is possible when mirror reflectivities are ultra-high. This approach to making absorption measurement provides a sensitivity independent versus noise or fluctuation of optical source intensity.