I enjoyed quite a lot in reading a nice work from S. Hell's group, namely "Nanometer resolution imaging and tracking of fluorescent molecules with minimal photon fluxes",published recently in Science, but a free version available on arxiv;
The core idea of this paper is to use the absolute zero intensity at the singular point of an ideal donut beam to perform positioning microscopy like PALM/STORM. When fluorescence molecule are exactly at this point, it will emit no photon, the nearer the fluorescent molecule is to the singular point, the emitting photon is less. Finding the minimum of minimum photon emission leads to the determination of the position of the fluorescent molecule. It is really clever idea and a marvelous improvement with much less photon required to achieve 1nm resolution.
Some nice early works applying singular optics to metrology can be found in Joseph Shamir's work "Singular beams in metrology and nanotechnology". And Zheng Xi also proposed to use this singularity to perform position sensing: "Accurate Feeding of Nanoantenna by Singular Optics for Nanoscale Translational and Rotational Displacement Sensing" with a free version on arxiv.
All these demonstrates useful applications of optical singularity, I believe many more nice works will pop out in this field.
