Tight Focusing for Immersion Microscopy and STED Microscopy

Tight focusing by high-NA objective lenses, which generates a small PSF (Point Spread Function), is essential for high-resolution microscopy systems. Among many other microscopy systems, immersion microscopy uses a coverslip to separate the immersion liquid and the specimen. It may distort the PSF at the focal plane. We demonstrate that the asymmetric PSF is further elongated behind the coverslip.  Moreover, STED (stimulated emission depletion) microscopy, which is widely used for tens-of-nanometer resolution, requires a donut-shaped PSF for depletion. We follow the proposed method by P. Török and P.R.T Monro to model the tight focusing of a Gaussian-Laguerre beam. The generation of a donut-shaped PSF is demonstrated.  

Tight Focusing by a High-NA Immersion Microscope

In VirtualLab Fusion, the influence of the interface of the coverslip on the PSF can be analyzed in a straightforward manner. The distortion of the focal spot behind the coverslip is demonstrated and analyzed in a fully vectorial manner. 

Focusing of Gaussian-Laguerre Beam for STED Microscopy

It is demonstrated that the focusing of a high-order Gaussian-Laguerre beam generates a donut-shaped PSF. The size of said donut-shaped PSF depends, among other variables, on the specific order of the beam. 

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