# The noise-limited-resolution for stimulated emission depletion microscopy

## TL;DR

This paper analyzes the fundamental noise limits of STED microscopy in diffusive regimes, revealing that resolution is constrained by thermal motion and photon statistics rather than saturation intensity.

## Contribution

It provides a theoretical analysis showing that, under diffusion, STED resolution depends on thermal motion and photon count, not on fluorescent saturation intensity.

## Key findings

- Resolution limited by thermal motion and photon count
- Noise-limited resolution independent of saturation intensity
- Thermal motion constrains signal integration time

## Abstract

With recent developments in microscopy, such as stimulated emission depletion (STED) microscopy, far-field imaging at resolutions better than the diffraction limit is now a commercially available technique. Here, we show that, in the special case of a diffusive regime, the noise-limited resolution of STED imaging is independent of the saturation intensity of the fluorescent label. Thermal motion limits the signal integration time, which, for a given excited-state lifetime, limits the total number of photons available for detection.