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2The 30th International Conference on Advanced Laser Technologies ALT'23
LM-I-25
Photovoltaic tweezers on the base of diffusion structures LiNbO3:Cu
S. Shandarov1, A. Kolmakov1, R. Anisimov1, A. Temereva1, K. Mambetova1, E. Komov1
1- Tomsk State University of Control Systems and Rarioelectronics, 40 Lenin Avenue, Tomsk 634050, Russia
stanislavshandarov@gmail.com
Strong inhomogeneous evanescent electric fields generated above the surface of lithium niobate crystals due to photovoltaic effect are successfully used to realization of optical tweezers [1,2]. The advantages of photovoltaic tweezers over the other optical manipulators consist of possibility for repeated using of mono-crystal substrates as well as in minimization of an overheating for captured objects at the expense of application the low-power radiation [3]. The lithium niobate crystals doped by photovoltaic impurities such as Fe [1,3] and Cu [2] are usually used in the capacity of substrate for the photovoltaic manipulation of nanoparti-cles. The surface character of evanescent electric fields used for realization of photovoltaic tweezers makes it attractive to apply diffusion doping of lithium niobate substrate by photovoltaic impurities [2,4].
In this work we present the results of experimental realization of the technology of diffusion doping of X-and Z-cut congruent lithium niobate crystals by copper and the results of studying their photorefractive and photovoltaic properties, which determine the effectivity of aggregation of dielectric nanoparticles on the surface of the fabricated LiNbO3:Cu samples. The process of copper diffusion into the substrates involved deposition of the Cu films with thickness of 400 nm on the related polished surface by thermal evaporation in a vacuum. The diffusion carried out at temperatures of 1000 °C and 600 °C for the samples with X- and Z-orientation respectively during the time from 5 h to 9 h.
To obtain the concentration distribution for copper ions existing in the LiNbO3 lattice in Cu+ and Cu2+ charge states the dependences of absorption coefficients on the depth from the X- and Z-surfaces for the light with the wavelengths of 532 and 808 nm respectively were experimentally investigated. It was established that these dependences characterized by nonmonotonic behavior. In addition, the positions of maxima for concentration of Cu+ and Cu2+ might be differ. Because of that, we have theoretically considered the formation of dynamic photorefractive gratings by a high-contrast interference pattern of writing laser beams in an X-cut plate of LiNbO3:Cu crystal with two different gaussian distributions for concentration of Cu+ and Cu2+ ions on the base of approach described in Ref. 4. The theoretical modeling for distribution of electric field of the photorefractive dynamic hologram on the depth from the X-surface in the crystal as well as of an evanescent field above the one is performed.
The experimental study of time evolution for diffraction effectivity of dynamic photorefractive holograms in the LiNbO3:Cu crystal allow us to estimate of Glass constant of diffusion layer for laser wavelength of 532 nm as well as to determine the optimal conditions for aggregation of dielectric nanoparticle on its surface.
This study was funded by the Ministry of Science and Higher Education of the Russian Federation in the framework of the state assignment for 2023-2025 (job-order FEWM-2023-0012).
[1] J. Villarroel, H. Burgos, A. Garcia-Cabanes, M. Carrascosa, A. Blazqcutuez-Castro A., and F. Agullo-Lopez, Photovoltaic versus optical tweezers, Opt. Express, vol. 19, pp. 24320-24330 (2011).
[2] K.M. Mambetova, S.M. Shandarov, A.I. Tatyannikov, and S.V. Smirnov, Aggregation of dielectric nanoparticles on the X-cut of LiNbO3 crystal by electric field of photorefractive holograms, Russian Physics Journal, vol. 62, pp. 658-663, (2019).
[3] A. Blazquez-Castro, A. Garcia-Cabanes, M. Carrascosa, Biological applications of ferroelectric materials, Appl. Phys. Rev., vol. 5, pp. 041101 (2018).
[4] K.M. Mambetova, S.M. Shandarov, L.N. Orlikov, S.I. Arestov, S.V. Smirnov, L.Ya. Serebrennikov, and V.A. Krakovskii, Formation of dynamic photorefractive gratingsin a LiNbO3:Cu surface-doped crystal, Optics and Spectroscopy, vol. 126, pp. 781-786 (2019).
