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Raman spectra of tryptophan and tyrosine polycrystals have been analyzed in a wide spectral range by fiber-optic spectroscopy. The Raman spectra have been recorded with a BWS465-785H spectrometer in the spectral range of 0–2700 cm–1 using a 785-nm cw laser as an excitation source. Parameters of the Raman spectra are compared for three crystalline phase modifications of aromatic amino acids: left-handed, right-handed, and racemic phase. The presence of strong Raman satellites, the characteristics of which change depending on the type of the chiral phase state of amino acid, is found in the low-frequency Raman spectra of tryptophan and tyrosine amino acid lattices. The results obtained can be used for monitoring the chiral purity of bioactive preparations containing amino acids.

Raman scattering spectra in the frequency range of 5–75 cm–1 in lithium niobate samples with various structural imperfections were obtained. It is shown that the intensity of quasi-elastic light scattering on the wing of the Rayleigh line demonstrates an exponential dependence on the concentration of large-scale defects in the samples. Calibration curves for the intensity of quasi-elastic scattering dependence at low frequencies on the acoustic quality factor are constructed.

The photoluminescence spectra of three crystalline phase modifications of aromatic amino acid tryptophan are compared: the left phase of L-tryptophan, the right phase of D-tryptophan, and the racemic phase of DL-tryptophan. The photoluminescence spectra were recorded using a fiber-optic procedure, a small-size FSD-8 spectrometer, and a data processing system that enables comparison of the analyzed spectrum with the spectrum of a reference substance. Photoluminescence was excited by a pulsed-periodic ultraviolet laser at a wavelength of 266 nm.

The structural phase transition in the Pr3Sb5O12 crystal has been studied using Raman spectroscopy. The phase transition is accompanied by the recovery of the soft mode below T = 735 K, which is associated with the displacements of the oxygen and antimony atoms.

A fiber-optic technique for measuring Raman scattering and photoluminescence spectra, based on fiber-optic cells (photon traps), a compact spectrometer, and a data processing system is developed. The system allows comparison of an analyzed spectrum with a reference material spectrum. Secondary emission spectra were excited using a solid-state laser with a wavelength of 532 nm. It is found that the secondary emission intensity significantly increased when adding an Al2O3 nanopowder to a studied material. Secondary emission spectra of a number of molecular compounds, pharmaceutical preparations, and minerals are studied.

The interaction of electromagnetic radiation with nanoscale particles systems (including suspension of metallic dielectric and semiconductor nanoparticles, biological nanostructures, etc.) can lead to various non-linear effects, in particular, to the stimulated low-frequency Raman scattering (SLFRS). It can provide important information about investigated system elastic properties. In the present study low-frequency vibrational modes in different biological nanoparticles systems were investigated, such as tobacco mosaic viruses (TMV), two types of potato viruses (PVX and PVA), cauliflower mosaic virus (CaMV), human and bovine serum albumin (HSA and BSA) in Tris-HCl pH7.5 buffer and in water. 20 ns ruby laser pulses were used for excitation. SLFRS frequency shifts, corresponding to acoustic eigenfrequencies of the samples were registered by Fabri-Perot interferometers. Conversion efficiency and threshold were also measured for the first time. SLFRS can be applied for nanoobjects identification and effective impact on biological nanoparticles systems.

The photoluminescence spectra of aromatic compounds in a photon trap under ultraviolet pulse-periodic excitation are recorded. It is shown that the photoluminescence spectrum shape depends on the material layer thickness in a cell, physical state of the sample, and exciting radiation characteristics: as the layer thicknesses decreases, the intensity is significantly redistributed, which is explained by the transition from spontaneous luminescence to superluminescence.

A method for diagnosing the molecular structure and composition of aromatic bioactive preparations is developed by the example of pharmaceutical objects: analgin, citramon, aspirin, and paracetamol. The method is based on fiber-optic measurements of fluorescence spectra upon laser ultraviolet (266 nm) excitation with high (0.1 mm) spatial resolution. It is shown that the inhomogeneity of a pharmaceutical preparation containing several components is observed at a distance of a few millimeters. Difference fluorescence spectra are constructed, which allow detection of differences in preparation compositions and structures even in the case of closeness of their fluorescence spectra. The developedmethod can be used to control quality of a large class of bioactive structures luminescing under ultraviolet light.

LiNbO3 exists in two forms: Most commercial devices are inexpensively fabricated from congruent melt that is ca. 1.5% off-stoichiometry. This produces devices of high optical quality for nonlinear optics but also high loss. Stoichiometric lithium niobate also exists, but in smaller more expensive specimens. Here we report the preparation and characterization of low-loss congruent samples. These are shown to be relatively free from extended defects. Publisher PDF