Spectrum data processing in optical-feedback cavity ring-down spectroscopy

In optical-feedback cavity ring-down spectroscopy (OF-CRDS), the data processing of the measured spectrum is often a troubling problem for a special spectral phenomenon called spectral ripple. With an OF-CRDS example of H2O molecule in the spectral range of 6 590.8-6 591.6 cm-1, a data processing method based on the characteristics analyses of spectral ripple is demonstrated. The linewidth of the H2O molecule at 6 590.871 cm-1 is determined as about 0.100 3 cm-1 with this method and its difference compared to the calculated result from Hitran database is 0.002 cm-1, which verifies the effectiveness of this method.