Induced gyrotropy in thin PET films before and after swift heavy ion irradiation evidenced from analysis of optical interference fringes
Tuleushev A.Z. Harrison F.E. Kozlovskiy A.L. Zdorovets M.V.
January 2022Elsevier B.V.
Optical Materials
2022#123
We present here experimental studies of the UV/vis/near IR transmission spectra of polyethylene terephthalate (PET) films before and after irradiation with Kr+15 ions of energy 1.75 MeV/a.u. and fluence of 1.9 × 10 10 cm−2. Our data show small variations (∼0.5%) in transmission between individual pristine PET film samples in the IR region of the spectrum, as would be expected for films produced to certain manufacturing tolerances. Swift heavy ion (SHI) irradiation of a sample reduces transmission in this region, but by less than the observed variation in transmission between individual pristine samples, and does not affect local transmission variations in the spectrum, indicating that SHI irradiation has not destroyed the molecular structure of the PET film responsible for these variations. We use established methods to separate our experimental spectra into interference-free transmission spectra and isolated interference fringes and estimate the absorption coefficient and dispersion of the refractive index for pristine and irradiated PET films. We show that the observed amplitude modulation of the interference fringes is due to the optical activity of our PET samples and is a signature of induced gyrotropy. In some spectral regions, we observe a refractive index that is negative relative to the Cauchy approximation. We provide evidence that this is due to the ordering/texture of chiral molecules in PET films, suggesting that very highly textured PET films may exhibit a greater degree of negativity.
Chirality , Induced gyrotropy , Interference fringes , Negative fraction of refractive index , PET film , Swift heavy ion irradiation
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Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna, Moscow Region, 141980, Russian Federation
Engineering Profile Laboratory, L.N. Gumilyov Eurasian National University, Nur-Sultan, 010008, Kazakhstan
Laboratory of Solid State Physics, The Institute of Nuclear Physics, Almaty, 050032, Kazakhstan
Department of Intelligent Information Technologies, Ural Federal University, Yekaterinburg, 620075, Russian Federation
Flerov Laboratory of Nuclear Reactions
Engineering Profile Laboratory
Laboratory of Solid State Physics
Department of Intelligent Information Technologies
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