Nanooptics and photonics 
Optical properties of polyvinylidene fluoride nanolayers
Ilchenko S.G.1, Multian V. V.2, Lymarenko R.A.1, Taranenko V.B.1, Salvatore. A.Pullano3,Antonino S.Fiorillo3, Gayvoronsky V. Ya.2 
1 International Center “Institute of Applied Optics” National Academy of Science of Ukraine10G Kudryavska street, Kyiv, 04053, Ukraine.
E-mail: Svitlana-ilchenko@ukr.net
2 Institute of Physics NAS of Ukraine, Prospect Nauky 46, 03028, Kyiv, Ukraine
3 Department of Health Sciences University Magna Græcia Catanzaro, 88100, Italy

Polyvinylidene fluoride (PVDF) is a semi-crystalline, high purity thermoplastic fluoropolymer. The C–F bonds are polar, and the highest dipole moment is obtained with the alignment of all dipoles of the polymer in the same direction, corresponding to the β-phase of the PVDF, which has piezoelectric characteristics of the polymer. PVDF attracted much attention due to its unique properties, such us light weight, mechanical toughness, chemical inertness, radiation hardness, optical transparency, both piezo- and pyro-electric effects and therefore it is widely used in sensors manufacturing, tissue engineering, energy storage devices and drug delivery systems.
We carried out optical measurements of β-phase PVDF films of various thicknesses. The influence of the formation of the structure of the films was studied by analyzing the linear and nonlinear optical responses. The optical quality of polymer films was characterized by the transmission spectra in UV-VIS ranges and the angular distribution of scattered light in the visible and near-IR. 
Upon excitation by single picosecond pulses at a wavelength of 1064 nm, the processes of generation of the second (532 nm) and third (355 nm) optical harmonics were studied [1]. The third harmonic generation with effective cubic nonlinear susceptibility about χ(3)(3ω) ~1.8÷1.9×10-14 esu was obtained on the PVDF films. 
The effects of self-action in the β-phase PVDF films with continuous emission of a He-Ne laser at a wavelength of 633 nm are investigated. It was shown that the samples have a self-focusing effect, which corresponds to a negative photo-induced change in the refractive index.
Studying the properties and dynamics of structural relaxation of a PVDF thin film and a P(VDF-TrFe) copolymer by means of optical harmonics generation can be a constructive approach for optimizing the response of sandwich structures with a polymer film and a nanoscale metal layer.

1. V.V.Multian, R.Le Dantec, V.Ya.Gayvoronsky. Characterization of colloidal nanoparticle suspensions using the third harmonic generation at interfaces // Ukrainian Journal of Physical Optics. - March 2018. - 19(2):92-98