S. Sainov

Simple laser microrefractometer

A new simple method for determining the magnitude of the refractive index of small volumes of liquid is proposed. The results obtained are close to the expected within the accuracy of the goniometer utilized.

Optical properties of photopolymerizable nanocomposites containing nanosized molecular sieves

Acrylamide-based photopolymerizable nanocomposites containing three types of nanosized crystals with controlled microporosity, Silicalite-1 (MFI-structure), AlPO-18 (AEI-structure) and Beta (BEA-structure) are studied. The influence of the porous nanoparticles on the average refractive index, optical scattering and holographic recording properties of the nanocomposite are characterized. The redistribution of nanoparticles as a result of the holographic recording in the layers is investigated by Raman spectroscopy. It is observed that in all three nanocomposites the nanoparticles are redistributed according to the illuminating light pattern. This redistribution improves the refractive index modulation only in the case of the MFI nanoparticles, while no improvement is observed in AEI and BEA doped layers. The results can be explained by the hydrophobic/hydrophilic nature of the nanoparticles and their interactions, or absence of interactions, with the host photopolymer.

High spatial frequency evanescent wave holographic recording in photopolymers

In the present work we report the results of holographic recording with two contra-propagating evanescent waves in photopolymers. The spatial frequency of the recorded permanent grating is 6380 mm−1 (grating step 156.7 nm) and 0.015% diffraction efficiency at 514.5 nm is achieved. The angular selectivity of the recorded evanescent grating is investigated at 632.8 nm. The maximum diffraction efficiency value is obtained at a critical angle of 60.1° ± 0.2° to the boundary with the total internal reflection prism, that determines the average refractive index of the grating of 1.501 ± 0.003. This is in good agreement with independent refractometric measurements and with theoretical expectations. A simple theoretical analysis of the evanescent wave holographic recording is made taking into account weak light absorption by the recording second medium. The close analogy with the attenuated total internal spectroscopic method is emphasized.

Total internal reflection holographic recording in very thin films

We present a theoretical background and experimental verification of holographic recording in nano-sized films. The interference pattern is created by a total internal reflected (TIR) reference wave and normally incident plane one. Due to a surface-propagating evanescent wave, the holographic recording is stored in 39 nm arsenic trisulfide film. The exposure and modulation dependence on the diffraction efficiency is investigated. The angular and wavelength selectivity of the thin TIR hologram is shown to be similar to that of thick Bragg gratings.

Refractive index investigation of poly(vinyl alcohol) films with TiO2 nanoparticle inclusions.

The refractive index (RI) of polymer nanocomposite of poly(vinyl alcohol) films with TiO(2) nanoparticle inclusions with low concentration up to 1.2 wt. % was investigated. Accurate refractometric measurements, by a specially designed laser microrefractometer, were performed at wavelengths 532 and 632.8 nm. The influence of TiO(2) concentration on the RI dispersion curves was predicted based on the well-known Sellmeier model. The theoretical analysis, in a small filling factor approximation, was performed, and a relation between the effective RI of the nanocomposite and weight concentrations of the TiO(2) nanofiller was derived. The experimental values were approximated by two different functions (linear and a quadratic polynom). The polynomial approximation yields better result, where R(2)=0.90.

Differential laser microrefractometer

A simple method for comparing simultaneously the refractive indices of more than two liquids is described. The results from the measurement of the water solution of sucrose confirm the linear dependence of the refractive index on concentration. Accuracy of 0.001% is obtained experimentally.

Using a total internal reflection diffraction grating for investigating absorbing liquids

Abstract A theoretical and experimental investigation is made into the possibility of using a diffraction grating operating in total internal reflection (TIR) for studying the properties of light absorbing liquids. The high sensitivity of the proposed method for detecting small changes in the concentration of the investigated medium is demonstrated. Changes in the diffraction efficiency were observed in successive two-fold decreases leading to a 2048 times decrease in the initial concentration in total (C 0 = 1·56 × 10 -4 mol litre -1 of a water solution of methylene blue.

Wide-spectral-range laser refractometer

We present refractometric measurements made in the 266-1064-nm spectral region with a pulsed Nd:YAG laser, and the second, third, and fourth harmonics of the lasers fundamental wavelength. The critical angle is determined by the disappearance of the diffraction orders from a metal grating, forming a microcuvette with the prisms reflecting wall. A fused-silica measuring prism is used in the experiments.

DESIGN AND TEST OF A SIMPLE HIGH-TEMPERATURE LASER MICROREFRACTOMETER

The design of a laser microrefractometer that is suitable for temperature-dependent measurements is described. The refractive index of methylene iodide is measured in the temperature range of 22-92 °C for laser wavelengths covering almost the entire visible range of the spectrum: 442, 488, 515, 543, 594, and 633 nm. A detailed analysis of the temperature-related experimental error is made.

Selected Physical Properties of Lime Bee Honey in Order to Discriminate Between Pure Honey and Honey Adulterated with Glucose

The refractive index, conductivity, optical rotation, thermophysical parameters, and infrared spectra of bee honey samples, as well as the content of β-carotene and potassium, were determined with a view to discriminate between pure honey and honey adulterated with glucose. The glass transition temperature and the optical rotation may be used for qualitative assessment of honey adulteration with glucose. Another indication of lime honey adulterated with glucose was the β-carotene content below 20 ppm and the potassium content below 200 ppm. The minimum detectable amount of glucose adulterant was 25 g in 100 g honey.