Joseph T. Hodges, A. Cygan, P. Wcislo, S. Wojtewicz, Piotr Maslowski, R. Ciurylo, D Lisak
Recent developments in optical metrology have tremendously improved the precision and accuracy of the horizontal (frequency) axis in measured spectra. However, the vertical (typically absorbance) axis is usually based on intensity measurements that are subject to instrumental errors which limit the spectrum accuracy. Here we report a one-dimensional dispersion method that uses only the measured frequencies of high-finesse cavity modes to provide complete information about the absorptive and dispersive properties of the spectrum. Because this technique depends solely on the measurement of optical frequency differences, it is insensitive to systematic errors in the detection of light intensity and has the potential to become the most accurate method for measuring absorption and dispersion spectra. The experimental results are compared to measurements by two other high-precision cavity-enhanced spectroscopy methods. We expect that the proposed technique will have significant impact in fields such as fundamental physics, gas metrology and environmental remote sensing.