How the concept of evanescent point sources contributes to the understanding of microsphere-assisted microscopy (Conference Presentation)

Microsphere-assisted microscopy is an imaging method that allows label free full field super-resolution to be achieved by adding a microsphere onto the sample under the microscope objective. Resolution improvement (a fifth of the wavelength in air and a seventh of the wavelength in immersion) has been experimentally demonstrated. However, the physical explanation of this resolution is not clear. We thus introduce the concept of the evanescent point source and its role in microsphere imaging. In a classical point source, typically a Rayleigh dipole, evanescent and propagative waves are intrinsically linked. On the contrary, the proposed evanescent point source is a local maximum fully composed of evanescent waves. We show how this allows the microsphere imaging process to be more clearly understood by also considering the coherence of the light involved.