Elen Tolstik

Non-local response in glass-like polymer storage materials based on poly (methylmethacrylate) with distributed phenanthrenequinone.

The development of volume phase gratings written by two-wave-mixing in glass-like polymer storage materials based on poly (methylmethacrylate) and its thermostable derivative (copolymer with acrylic acid) with distributed phenanthrenequinone is investigated experimentally and theoretically. The maximal diffraction efficiency is considered in dependence on the grating period. The redistribution processes of the molecules are described with a one-dimensional diffusion model yielding the existence of a non-local response in the photopolymer layer, and the corresponding non-local response length of phenanthrenequinone is found experimentally.

Numerical investigation of the (1+1)D self-trapping of laser beams in polymeric films based on polymethylmethacrylate and phenanthrenequinone

An analytical description connected with a numerical calculation of the propagation of self-trapped laser beams in a polymethylmethacrylate matrix containing phenanthrenequinone molecules is presented. A theoretical model for the spatial distribution of boundary optical waves is developed in dependence on characteristic beam parameters.

PMMA-PQ Photopolymers for Head-Up-Displays

We present the experimental realization of a head-up-display based on a photopolymer. A phase volume reflection hologram is written in a photopolymer layer and is used as a screen for a signal beam. To write efficient holograms in the polymeric material we used ordinary and modified polymethylmethacrylate matrices containing phenanthrenequinone (PQ). Increasing the PQ concentration gives us an opportunity to realize thinner layers (<100 mum) saving high values of the diffraction efficiency. Decreasing the thickness of the layer allows higher observation angles of the received image and a wider spectral range of the incident light.

Studies of silicon nanoparticles uptake and biodegradation in cancer cells by Raman spectroscopy

In-vitro Raman micro-spectroscopy was used for diagnostics of the processes of uptake and biodegradation of porous silicon nanoparticles (SiNPs) in breast cancer cells (MCF-7 cell line). Two types of nanoparticles, with and without photoluminescence in the visible spectral range, were investigated. The spatial distribution of photoluminescent SiNPs within the cells obtained by Raman imaging was verified by high-resolution structured-illumination optical microscopy. Nearly complete biodegradation of SiNPs inside the living cells was observed after 13days of the incubation. The results reveal new prospects of multi-modal visualization of SiNPs inside cancer cells for theranostic applications.

Broadening of the light self-trapping due to thermal defocusing in PQ-PMMA polymeric layers

The channel formation by the self-trapping of a (1 + 1)D beam in polymeric media based on a polymethylmethacrylate (PMMA) matrix containing phenanthrenequinone (PQ) molecules is predicted theoretically and observed experimentally for the first time. Particular attention is paid to the effect of thermal beam expansion, which in conjunction with the photorefractive nonlinearity of the medium results in the possibility to control optically the geometrical parameters of the generated channel.

Formation of self-trapping waveguides in bulk PMMA media doped with Phenanthrenequinone

Experimental and theoretical investigations of light self-trapping waveguides in a bulk polymeric medium based on polymethylmethacrylate (PMMA) with photosensitive phenanthrenequinone (PQ)-molecules are examined. Self-channeling was generated for the first time in this nonlinear bulk PQ-PMMA media with a thickness up to several millimeters and 0.1 mol. % PQ-concentration. The experimental formation of volume waveguide structures with a length of 2 - 3 cm at different laser wavelengths (405 nm, 488 nm, and 514.5 nm) was demonstrated. The calculations based on a model for the laser beam propagation in the bulk PQ-PMMA medium with competitive nonlinearities are in a good agreement with the experiments.

Optical Sectioning and High Resolution in Single-Slice Structured Illumination Microscopy by Thick Slice Blind-SIM Reconstruction

The microscope image of a thick fluorescent sample taken at a given focal plane is plagued by out-of-focus fluorescence and diffraction limited resolution. In this work, we show that a single slice of Structured Illumination Microscopy (two or three beam SIM) data can be processed to provide an image exhibiting tight sectioning and high transverse resolution. Our reconstruction algorithm is adapted from the blind-SIM technique which requires very little knowledge of the illumination patterns. It is thus able to deal with illumination distortions induced by the sample or illumination optics. We named this new algorithm thick slice blind-SIM because it models a three-dimensional sample even though only a single two-dimensional plane of focus was measured.

Linear and Non-Linear Optical Imaging of Cancer Cells with Silicon Nanoparticles

New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10–40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours.

New thermostable copolymers for holographic storage based on methylmethacrylate with methacrylamide or methacrylic acid

Two new copolymers based on methylmethacrylate (MMA) with methacrylamide (MAA) and methacrylic acid (MA) containing distributed phenanthrenequinone (PQ) molecules are fabricated for the purpose of optical recording by generating holographic diffractive structures under argon laser illumination. Chemical conditions for the formation of holograms are discussed and confirmed by the spectral characteristics of the material. Thermal and adhesive properties were improved with the aim of expanding the range of polymer application and generating of diffractive elements with long term stability and high optical quality.

Highly concentrated phenanthrenequinone – polymethylmethacrylate composite for thick reflection holograms recording at 532 nm

The formation of stable phase reflection holograms in highly-concentrated phenanthrenequinone - polymethylmethacrylate (PQ-PMMA) layers with a thickness of about 100 µm at 532 nm recording wavelength has been investigated. In spite of the low absorbance of the photosensitive material at the long wave edge of the absorption spectrum, a refractive index modulation of 4.2·10−4 close to the practically reachable limit was achieved during the optical recording. Quantitative investigation of thermal and light treatment of the recorded holograms has demonstrated a tenfold increase of the diffraction efficiency (up to 60%) without disturbing the angular selectivity profile.