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1

Engineering the point spread function of layered metamaterials

Pastuszczak A., Stolarek M., Kotyński R.

Opto-Electronics Review

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2013

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Vol. 21, No. 4

355-366

EN

Layered metal-dielectric metamaterials have filtering properties both in the frequency domain and in the spatial frequency domain. Engineering their spatial filtering response is a way of designing structures with specific diffraction properties for such applications as sub-diffraction imaging, supercollimation, or optical signal processing at the nanoscale. In this paper we review the recent progress in this field. We also present a numerical optimization framework for layered metamaterials, based on the use of evolutionary algorithms. A measure of similarity obtained using Hölder’s inequality is adapted to construct the overall criterion function. We analyse the influence of surface roughness on the quality of imaging.

2

Sensitivity of imaging properties of metal-dielectric layered flat lens to fabrication inaccuracies

Kotyński R., Baghdasaryan H., Stefaniuk T., Pastuszczak A., Marciniak M., Lavrinenko A., Panajotov K., Szoplik T.

Opto-Electronics Review

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2010

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Vol. 18, No. 4

446-457

EN

We characterize the sensitivity of imaging properties of a layered silver-TiO₂ flat lens to fabrication inaccuracies. The lens is designed for approximately diffraction-free imaging with subwavelength resolution at distances in the order of a wavelength. Its operation may be attributed to self-collimation with a secondary role of Fabry-Perot resonant transmission, even though the first order effective medium description of the structure is inaccurate. Super-resolution is maintained for a broad range of overall thicknesses and the total thickness of the multilayer is limited by absorption. The tolerance analysis indicates that the resolution and transmission efficiency are highly sensitive to small changes of layer thicknesses.

3

Fourier optics approach to imaging with sub-wavelength resolution through metal-dielectric multilayers

Kotyński R.

Opto-Electronics Review

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2010

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Vol. 18, No. 4

366-375

EN

Metal-dielectric layered stacks for imaging with sub-wavelength resolution are regarded as linear isoplanatic systems - a concept popular in Fourier optics and in scalar diffraction theory. In this context, a layered flat lens is a one-dimensional spatial filter characterised by the point spread function. However, depending on the model of the source, the definition of the point spread function for multilayers with sub-wavelength resolution may be formulated in several ways. Here, a distinction is made between a soft source and hard electric or magnetic sources. Each of these definitions leads to a different meaning of perfect imaging. It is shown that some simple interpretations of the PSF, such as the relation of its width to the resolution of the imaging system are ambiguous for the multilayers with sub-wavelenth resolution. These differences must be observed in point spread function engineering of layered systems with sub-wavelength sized PSF.

4

Optical correlator with variable discrimination capability-experimental results.

Millan M., S., Perez E., Kotyński R., Chałasińska-Macukow K.

Optica Applicata

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2000

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Vol. 30, nr 2-3

291-302

EN

In many pattern recognition applications it is required that the discrimination capability should be tunable. We propose and develop an optical set-up in which the discrimination capability could be continuously varied within a large range. Our set-up is based on the two-step, JTC architecture. The pattern recognition algorithm that we realize using the set-up is the dual nonlinear correlation (DNC), which is a generalization of a number of popular filtering methods. The paper contains the results obtained numerically in a simulated optical set-up as well as the experimental results obtained in the optical correlator, which we built using two different SLMs. We analyse the correlator performance according to the different characteristics of the SLM panels.

5

BPOF composite filter optimized with a genetic algorithm.

Kotyński R., Chałasińska-Macukow K.

Optica Applicata

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2000

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Vol. 30, nr 2-3

303-316

EN

We introduce a new composite Fourier-plane binary phase-only correlation filter (BPOF). The filter is defined with the use of a nonquadratic energy function and is optimized numerically with a variant of the genetic algorithm. A possible application of the filter could include automatic postcode recognition. The paper also contains an introduction to composite filtering and a short overview of the present state of technology in the field of coherent optical correlators.