We report on a new method of inspecting deep microstructures manufactured in transparent media. Although their lateral dimension (tens of microns) do not exceed the diffraction limit for optical microscopy resolution, their deepness makes the nondestructive measurements practically impossible with presently available methods. We show that the optical vortex interferometer with a vortex generator can be used to differentiate between the samples of good and poor quality. The measurement system is simple and the interpretation of the results is straightforward.

We investigate the diffraction effects of focused Gaussian beams yielding a double optical vortex by a nano-step structure fabricated in a transparent media. When approaching such a step the double vortex splits into single ones which move in a characteristic way. By observing this movement we can determine the position of the step with high resolution. Our theoretical predictions were verified experimentally.

We discussed a new scanning method for optical vortex-based scanning microscopy. The optical vortex is introduced into the incident Gaussian beam by a vortex lens. Then the beam with the optical vortex is focused by an objective and illuminates the sample. By changing the position of the vortex lens we can shift the optical vortex position at the sample plane. By adjusting system parameters we can get 30 times smaller shift at the sample plane compared to the vortex lens shift. Moreover, if the range of vortex shifts is smaller than 3% of the beam radius in the sample plane the amplitude and phase distribution around the phase dislocation remains practically unchanged. Thus we can scan the sample topography precisely with an optical vortex.

The Young's double-slit experiment is one of the most popular stories in the history of physics. This paper, like many others, has emerged from the Young's idea. It investigates the diffraction of the plane or spherical wave produced by three or four small holes in an opaque screen. It was noticed that the interference field contained a lattice of optical vortices which were equivalent to those produced in optical vortex interferometer. The vortex lattice generated by the three holes possessed some unique properties from which the analytical formulae for vortex points position were derived. We also pointed out the differences between our case and the double-slit experiment. Finally, some remarks on possible applications of our arrangement are discussed briefly. These theoretical considerations are illustrated with the use of experimental results.

No abstract