Spatial laser-wing suppression in saturated laser-induced fluorescence without spatial selection

Geometric determination of saturation in fluorescence spectroscopy

In laser spectroscopy, saturation of atomic or molecular transitions cannot be ignored, even at modest laser intensities. The saturation status is customarily diagnosed from measurements of saturation curves describing the dependence of spectroscopic signals on laser intensity. I propose an alternative method that relies on a geometric comparison of the spatial laser profile with images of the spectroscopic quantity under investigation. A single image can be used to determine the saturation status and its associated saturation laser intensity.

Fluorescence correlation spectroscopy: incorporation of probe volume effects into the three-dimensional Gaussian approximation

Fluorescence correlation spectroscopy is a valuable tool in many scientific disciplines. In particular, such a spectroscopic technique has received a great deal of attention because of its remarkable potential for single-molecule detection. It is understood, however, that quantitative measurements can be considered reliable as long as molecular photophysics has been well characterized. To that end, molecular saturation and probe volume effects, which can worsen experimental accuracy, are treated here. These phenomena are adequately incorporated into the well-known three-dimensional Gaussian approximation by a novel method applied to interpret saturated fluorescence signals [Opt. Lett. 28, 2016 (2003)]. Comparisons with literature data are given to show the improvements of the suggested method compared with other approaches.