# Saturated absorption competition microscopy

## TL;DR

Saturated absorption competition (SAC) microscopy is a novel fluorescence imaging technique that achieves sub-diffraction resolution using a simple setup with a single laser diode, emphasizing absorption competition rather than emission depletion.

## Contribution

This work introduces SAC microscopy, a new method that surpasses diffraction limits with lower complexity and cost compared to existing super-resolution techniques.

## Key findings

- Achieved ~lambda/6 spatial resolution in proof-of-concept experiments.
- Demonstrated SAC's effectiveness with a simple, cost-effective setup.
- Provided a physico-chemical model of the SAC process.

## Abstract

We introduce the concept of saturated absorption competition (SAC) microscopy as a means of providing sub-diffraction spatial resolution in fluorescence imaging. Unlike the post-competition process between stimulated and spontaneous emission that is used in stimulated emission depletion (STED) microscopy, SAC microscopy breaks the diffraction limit by emphasizing a pre-competition process that occurs in the fluorescence absorption stage in a manner that shares similarities with ground-state depletion (GSD) microscopy. Moreover, unlike both STED and GSD microscopy, SAC microscopy offers a reduction in complexity and cost by utilizing only a single continuous-wave laser diode and an illumination intensity that is ~ 20x smaller than that used in STED. Our approach can be physically implemented in a confocal microscope by dividing the input laser source into a time-modulated primary excitation beam and a doughnut-shaped saturation beam, and subsequently employing a homodyne detection scheme to select the modulated fluorescence signal. Herein, we provide both a physico-chemical model of SAC and experimentally demonstrate by way of a proof-of-concept experiment a transverse spatial resolution of ~lambda/6.

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Source: https://tomesphere.com/paper/1701.06358