Experimentální biofotonika

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Multimodal Holographic Microscopy: Distinction between Apoptosis and Oncosis
(PLOS, 2015-03-24) Balvan, Jan; Křížová, Aneta; Gumulec, Jaromír; Raudenská, Martina; Sládek, Zbyšek; Sedláčková, Miroslava; Babula, Petr; Svobodová, Markéta; Kizek, René; Chmelík, Radim; Masařík, Michal
Identification of specific cell death is of a great value for many scientists. Predominant types of cell death can be detected by flow-cytometry (FCM). Nevertheless, the absence of cellular morphology analysis leads to the misclassification of cell death type due to underestimated oncosis. However, the definition of the oncosis is important because of its potential reversibility. Therefore, FCM analysis of cell death using annexin V/propidium iodide assay was compared with holographic microscopy coupled with fluorescence detection Multimodal holographic microscopy (MHM). The aim was to highlight FCM limitations and to point out MHM advantages. It was shown that the annexin V+/PI phenotype is not specific of early apoptotic cells, as previously believed, and that morphological criteria have to be necessarily combined with annexin V/PI for the cell death type to be ascertained precisely. MHM makes it possible to distinguish oncosis clearly from apoptosis and to stratify the progression of oncosis.
Silicon waveguides with graphene: coupling of waveguide mode to surface plasmons
(IOP Publishing, 2020-08-18) Čtyroký, Jiří; Petráček, Jiří; Kuzmiak, Vladimír; Kwiecien, Pavel; Richter, Ivan
Silicon waveguides with graphene layers have been recently intensively studied for their potential as fast and low-power electro-optic modulators with small footprints. In this paper we show that in the optical wavelength range of 1.55 mu m, surface plasmons supported by the graphene layer with the chemical potential exceeding similar to 0.5 eV can couple with the guided mode of the silicon waveguide and affect its propagation. On the other hand, this effect might be possibly utilized in technical applications like a very low-power amplitude modulation, temperature sensing, etc.
Multimode fibre: Light-sheet microscopy at the tip of a needle
(Springer Nature, 2015-12-14) Plöschner, Martin; Kollárová, Věra; Dostál, Zbyněk; Nylk, Jonathan; Barton-Owen, Thomas; Ferrier, David E.K.; Chmelík, Radim; Dholakia, Kishan; Čižmár, Tomáš
Light-sheet fluorescence microscopy has emerged as a powerful platform for 3-D volumetric imaging in the life sciences. Here, we introduce an important step towards its use deep inside biological tissue. Our new technique, based on digital holography, enables delivery of the light-sheet through a multimode optical fibre – an optical element with extremely small footprint, yet permitting complex control of light transport processes within. We show that this approach supports some of the most advanced methods in light-sheet microscopy: by taking advantage of the cylindrical symmetry of the fibre, we facilitate the wavefront engineering methods for generation of both Bessel and structured Bessel beam plane illumination. Finally, we assess the quality of imaging on a sample of fluorescent beads fixed in agarose gel and we conclude with a proof-of-principle imaging of a biological sample, namely the regenerating operculum prongs of Spirobranchus lamarcki.
Automated alignment method for coherence-controlled holographic microscope
(SPIE, 2015-10-28) Dostál, Zbyněk; Slabý, Tomáš; Kvasnica, Lukáš; Lošťák, Martin; Křížová, Aneta; Chmelík, Radim
Coherence-controlled holographic microscope (CCHM) was developed particularly for quantitative phase imaging and measurement of live cell dynamics, which is the proper subject of digital holographic microscopy (DHM). CCHM in low-coherence mode extends DHM in the study of living cells. However, this advantage is compensated by sensitivity of the system to easily become misaligned, which is a serious hindrance to wanted performance. Therefore, it became clear that introduction of a self-correcting system is inevitable. Accordingly, we had to devise a theory of a suitable control and design an automated alignment system for CCHM. The modulus of the reconstructed holographic signal was identified as a significant variable for guiding the alignment procedures. From this, we derived the original basic realignment three-dimensional algorithm, which encompasses a unique set of procedures for automated alignment that contains processes for initial and advanced alignment as well as long-term maintenance of microscope tuning. All of these procedures were applied to a functioning microscope and the tested processes were successfully validated. Finally, in such a way, CCHM is enabled to substantially contribute to study of biology, particularly of cancer cells in vitro.
Optical simulation of quantum mechanics on the Mobius strip, Klein's bottle and other manifolds, and Talbot effect
(IOP Publishing, 2021-03-01) Bělín, Jakub; Tyc, Tomáš; Horsley, Simon A. R.
We analyse the evolution of the wavefunction of a quantum particle propagating on several compact manifolds, including the Klein bottle, Mobius strip and projective plane. We find analytically the stationary states and the energy spectrum and show that the wavefunction exhibits perfect revivals. Using the orbifold structure of the discussed manifolds, we establish the relation of wave evolution on the manifolds to Fresnel diffraction and consequently to the Talbot effect. This connection provides a novel method of optical simulation of the quantum motion on compact manifolds. We discuss some novel phenomena as well as the effects of topology on the properties of the waves on the manifolds.

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