Influence of detector’s aperture on metrical precision of ring-down cavity

In order to study the metrical precision of reflectivity via cavity ring-down spectroscopy,first of all,it is investigated that influence of length misadjustment of ring-down cavity on its mode coupling.Then,based on propagation of Gaussian beam,it is deduced that relation between detector's aperture and output power of ring-down cavity of length misadjustment,and it is also numerically simulated that influence of detector's aperture on metrical precision.Results show that the bigger the detector's aperture is,the lower the metrical relative error is.