Influence of fluorescence time characteristics on the spatial resolution of CW-stimulated emission depletion microscopy

Abstract

As one of the most important realizations of stimulated emission depletion (STED) microscopy, the continuouswave (CW) STED system, constructed by using CW lasers as the excitation and STED beams, has been investigated and developed for nearly a decade. However, a theoretical model of the suppression factors in CW STED has not been well established. In this investigation, the factors that affect the spatial resolution of a CW STED system are theoretically and numerically studied. The full-width-at-half-maximum (FWHM) of a CW STED with a doughnut-shaped STED beam is also reanalyzed. It is found that the suppression function is dominated by the ratio of the local STED and excitation beam intensities. In addition, the FWHM is highly sensitive to both the fluorescence rate (inverse of fluoresce lifetime) and the quenching rate, but insensitive to the rate of vibrational relaxation. For comparison, the suppression function in picosecond STED is only determined by the distribution of the STED beam intensity scaled with the saturation intensity. Our model is highly consistent with published experimental data for evaluating the spatial resolution. This investigation is important in guiding the development of new CW STED systems.

Parametric investigations on the saturation intensity of Coumarin 102 for stimulated emission depletion application

“…As demonstrated by Qin et al . (), the depletion of CW STED is sensitive to the fluorescent quenching rate. The higher the quenching rate is, the weaker the depletion becomes.…”

“…The varying saturation intensity with P STED could be attributed to the changing of fluorescent quenching rate. As demonstrated by Qin et al (2018), the depletion of CW STED is sensitive to the fluorescent quenching rate. The higher the quenching rate is, the weaker the depletion becomes.…”