Polarimetric studies of L-arginine-doped potassium dihydrogen phosphate single crystals

M. Shopa , Y. Shopa, M. Shribak, I. Pritula, E. Kostenyukova, O. Bezkrovnaya – Journal of Applied Crystallography – 2020
Conoscopic interference patterns, channelled spectra and polarimetric techniques have been used for the characterization of pure and doped (with L-arginine amino acid) potassium dihydrogen phosphate (KDP) single crystals. Experimental polarimetric data have been obtained for the frequently used wavelength of 633 nm and for two close wavelengths of 532 and 543 nm in a high-accuracy dual-wavelength polarimeter. The measurement of eigenwave ellipticity in the [100] and [010] directions and between 295 and 340 K shows small differences in the absolute values of the specific optical rotations of KDP crystals doped with L-arginine in the range of 0.7–3.8 wt%. It is found that the gyration tensor component g11, specific optical rotation and eigenwave ellipticity show different dispersion in the visible spectral region.

Application of two-dimensional intensity maps in high-accuracy polarimetry

We propose the analysis of 2D intensity contour maps which is based on the optical transmission function for the polarizer-specimen-analyzer system. A small modification of the high-accuracy universal polarimeter (HAUP) technique was used to measure the intensity maps (HAUP maps) and determine the phase retardation, linear dichroism (LD) parameters, and multiple light reflection contribution in uniaxial crystals. We have performed measurements in a direction perpendicular to the optical axis on pure birefringent LiNbO3, birefringent optically active SiO2, and two birefringent optically active dichroic galogermanate crystals doped with Mn3+ and Cr3+ ions. We have obtained good agreement of the experimental data for 532, 633, and 650 nm wavelengths with analytical values. These results extend the capabilities of high-accuracy polarimetry to anisotropic crystal studies.

Optical activity and electro-optic effect of l-arginine doped KDP single crystals

M. Shopa , Y. Shopa, E. Kostenyukova, I. Pritula, O. Bezkrovnaya – OPTICS AND LASER TECHNOLOGY – 2019
We have used the modified polarimetric methods to study optical activity (OA) in the potassium dihydrogenphosphate (KDP) crystals doped with 0.7, 1.4 and 3.8 wt% L-arginine (L-arg) amino acid. Crystals were grown by the temperature reduction method. Small changes of the absolute eigen waves ellipticity and OA values in doped crystals were noted. We have experimentally determined the signs of OA in the [1 00] and [01 0] directions in KDP type crystals. The electro-optical parameters (half-wave voltage and electro-optical coefficients r63) in L-arg doped crystals for fixed wavelengths of 633, 532 and 405 nm remain unchanged in comparison with the pure KDP.

Investigations of the optical activity of nonlinear crystals by means of dual-wavelength polarimeter

M. Shopa , N. Ftomyn – OPTICAL ENGINEERING – 2018
A dual-wavelength method in high accuracy polarimetry has been successfully tested and applied to measure optical activity (OA) of nonlinear crystals. In proposed polarimetric scheme two neighboring semiconductor laser wavelengths (635 and 650 nm) are used, which increases number of parameters measured simultaneously and improves the data processing. By neglecting dispersion of eigen wave ellipticity in crystals, more efficient elimination of the systematic errors, in comparison with the known HAUP technique, is possible. We have tested our experimental setup on optically inactive lithium niobate crystal and obtained OA in the perpendicular to the optical axis direction for quartz and DKDP crystals.

Dual-wavelength laser polarimeter and its performance capabilities

M. Shopa , Y. Shopa, N. Ftomyn – OPTO-ELECTRONICS REVIEW – 2017
A dual-wavelength optical polarimetric approach has been proposed as a means of elimination of the systematic errors and estimation of the optical anisotropy parameters for a single DKDP crystal. Our HAUP-related polarimeter uses two semiconductor lasers with the neighbouring wavelengths of 635 nm and 650 nm. Based on the temperature dependence analysis of small characteristic azimuths of light polarization with respect to the axis of the sample, we found the parameters of imperfections of polarization system. We acquired eigen waves ellipticities in a DKDP crystal and found perpendicular to the optic axis value of the optical rotatory power. Our results correlate positively with previously measured data for KDP crystals.

Dual-wavelength polarimeter application in investigations of the optical activity of a langasite crystal

A method of high accuracy polarimetry, which includes optical activity measurements systematic errors, was realized with dual-wavelength polarimeter for two wavelengths of 635 and 650 nm. Simultaneous measurements with neighboring wavelengths significantly improved the data processing, by increasing the amount of data to eliminate the systematic errors. For langasite crystal La3Ga5SiO14 we measured temperature dependence of the gyration tensor component g11. Our acquired value doesn’t exceed 0.47×10–5 and is much smaller than previous results obtained by different experimental methods. Results presented in this paper correspond well with the calculated optical rotatory power from crystal structure data and polarizabilities of the atoms.

Calculation methods of interaction of electromagnetic waves with objects of complex geometries

Modeling of the electromagnetic interaction with different homogeneous or inhomo-geneous objects is a fundamental and important problem. It is relatively easy to solve Maxwellequations analytically when the scattering object is spherical or cylindrical, for example. How-ever, when it loses these properties all that is left for us is to useapproximation models, to ac-quire the solution we need. Modeling of complex, non-spherical, asymmetric particles is used tostudy cosmic, cometary dust, aerosols, atmospheric pollution etc. Few analytical, surface-basedand volume-based methods of light scattering modeling, most commonly used by scientists, arereviewed here