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The University of Southampton
Mathematical Sciences

Optimising optical super-oscillations for sub-wavelength focussing Seminar

Time:
12:00 - 14:00
Date:
15 November 2016
Venue:
Building 54, Room 5025 (Lecture Theatre B), University of Southampton, Highfield, Southampton, SO17 1BJ

For more information regarding this seminar, please telephone Professor Chris Howls on 023 8059 5145 or email C.J.Howls@southampton.ac.uk .

Event details

The resolution of conventional optical imaging is limited by diffraction – in general features smaller than approximately half the wavelength of the light being used cannot be resolved. Super-oscillatory imaging, pioneered at the University of Southampton, is one of a number of techniques being developed that can beat this limit and allow super-resolution imaging. One of the factors commonly used to explain the diffraction limit is the belief that band-limited signals cannot oscillate substantially faster than their fastest Fourier component. However, it has been shown that arbitrarily fast oscillations can occur in band-limited signals, in regions of low energy density. We refer to these fast oscillations as super-oscillations. In optics, super-oscillations mean that we can form arbitrarily small spots of light, surrounded by high-intensity side bands, by careful engineering the interference pattern. I will introduce the idea of super-oscillations, their relevance to optical imaging, and discuss my work on the optimisation of super-oscillatory spots. This optimisation problem takes into account the limitations that come from the imaging process: although arbitrarily small spots can be produced in theory, they cannot be used in practice. These interference patterns are created by optimising linear combinations of circular prolate spheroidal wave functions, which form a basis set of square integrable functions and are band-limited under the Hankel transform. I will present images using early results of this work, taken by collaborators in the Optoelectronics Research Centre and the Institute for Life Sciences at Southampton, of both engineered test samples and living cells. Finally, I will discuss the potential for improved optimisation techniques producing better spots, and also for fundamental results on the trade-offs inherent in super-oscillatory focussing.

Speaker information

Katrine Rogers, Open University.

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