Quantitative pupil analysis in stimulated emission depletion microscopy using phase retrieval.

Area of Science:

• Optical microscopy
• Super-resolution imaging
• Biophysics

Background:

• Stimulated emission depletion (STED) microscopy achieves high resolution by using a depletion beam to minimize the effective fluorescent spot size.
• The quality of the STED laser focus is critical for achieving optimal resolution in STED microscopy.
• Current methods for assessing focus quality, such as visual inspection, are subjective and provide limited quantitative information about aberration sources.

Purpose of the Study:

• To develop a non-invasive method for quantitatively assessing the quality of the STED laser focus.
• To identify and characterize aberration sources affecting STED microscopy performance.
• To enable accurate 3D reconstruction and correction of the STED focus.

Main Methods:

• A novel method was developed to obtain the complex pupil function at the objective's back aperture.
• This method requires no modifications to the existing STED microscope setup.
• The obtained pupil function was used to reconstruct the STED focus in three dimensions.

Main Results:

• The method provides quantitative information about aberrations, including those induced by the objective lens or the sample.
• The accuracy of the reconstructed pupil function was sufficient for precise STED focus characterization.
• The technique allows for the determination of specific corrective steps to mitigate aberrations.

Conclusions:

• The described method offers a powerful tool for routine quality control in STED microscopy.
• Quantitative aberration analysis enables optimization of STED imaging for enhanced resolution and image quality.
• This approach facilitates the identification and correction of optical aberrations, leading to more reliable super-resolution microscopy.