High-efficiency generation of harmonics in polythiophene
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Published:2021-05-01
Issue:5
Volume:51
Page:437-445
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ISSN:1063-7818
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Container-title:Quantum Electronics
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language:
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Short-container-title:Quantum Electron.
Author:
Vasenin N.T.,Ivanenko A.V.,Klement’ev V.M.,Kulik L.V.,Nevostruev D.A.,Nyushkov B.N.,Trashkeev S.I.,Khomyakov M.N.
Abstract
Abstract
High-efficiency harmonic generation is observed in a semiconducting polymer RR-P3HT [regioregular poly(3-hexylthiophene)], which exhibits a high nonlinear susceptibility [χ
(2) > 10−6 m V−1] under pumping by a pulsed fibre laser. The harmonic generation efficiency in RR-P3HT is comparable or higher than that observed for liquid crystals, which are used in reference experiments to estimate the susceptibility [the quadratic susceptibility of a nematic liquid crystal NLC 1289 is χ
(2) ≈ 2 × 10−6 m V−1]. No generation is observed in polythiophene with a random structure, RRa-P3HT [regiorandom poly(3-hexylthiophene)], at the same pump power. It is experimentally demonstrated that a necessary condition for generating the second and third harmonics in a polymer, along with a high pump power density, is the presence of a large power density gradient (exceeding 1013 W m−3). Based on a preliminary theoretical analysis, we can suggest that the quadrupole mechanism, which is a consequence of the regularity of RR-P3HT structure in the thin near-wall layer, may contribute significantly to the nonlinear radiation conversion in semiconducting polymers.
Subject
Electrical and Electronic Engineering,Atomic and Molecular Physics, and Optics,Statistical and Nonlinear Physics,Electronic, Optical and Magnetic Materials