@article{aaeb36ccb4084db38190c71b17cf87ac,
title = "Strong Nonlinear Optical Response in the Visible Spectral Range with Epsilon-Near-Zero Organic Thin Films",
abstract = "Enhanced Kerr nonlinearities are observed in metamaterials such as conducting oxides and doped inorganic semiconductor thin films showing epsilon-near-zero (ENZ) response in the infrared region. However, to achieve ENZ in the visible, artificial metamaterials with more complex nanostructures have to be specifically designed. Here, using sodium [5,6-dichloro-2-[[5,6-dichloro-1-ethyl-3-(4-sulphobutyl)-benzimidazol-2-ylidene]-propenyl]-1-ethyl-3-(4-sulphobutyl)-benzimidazolium hydroxide] and [2,4-bis[8-hydroxy-1,1,7,7-tetramethyljulolidin-9-yl]squaraine] organic thin films, ENZ responses between 450 and 620 nm are demonstrated. Both nonlinear refractive index and nonlinear absorption coefficient are enhanced by more than two orders of magnitude in the ENZ spectral region. These optical effects in the visible spectral range come from the strongly dispersive permittivity of molecular aggregates resulting from the coupling of excitonic transition dipoles. These findings open the path toward a next generation of high-performance solution-processable organic nonlinear optical materials with ENZ properties that can be tuned by molecular engineering.",
keywords = "epsilon near zero (ENZ), molecular aggregates, optical Kerr nonlinearity, organic thin film",
author = "Lee, {Yeon Ui} and Eleonora Garoni and Hanayo Kita and Kenji Kamada and Woo, {Byung Hoon} and Jun, {Young Chul} and Chae, {Sang Min} and Kim, {Hyo Jung} and Lee, {Kwang Jin} and Seokhyun Yoon and Eunyoung Choi and Fabrice Mathevet and Igor Ozerov and Ribierre, {Jean Charles} and Wu, {Jeong Weon} and Anthony D'Al{\'e}o",
note = "Funding Information: This work was carried out in the framework of CNRSUMI2002 2B-FUEL “Building Blocks for Future Electronics Laboratory” and CNRS International Associated Laboratory “Functional Nanostructures: Morphology, Nanoelectronics and Ultrafast Optics” (LIA NANOFUNC) and was supported by funding of the Ministry of Science, ICT & Future Planning, Korea (2014M3A6B3063706, 2017R1E1A1A01075394). This work was partially supported by a Grant-in-Aid for Scientific Research on Innovative Areas “Photosynergetics” (No. JP26107004, K.K.) from MEXT and a Grant-in-Aid for Scientific Research (No. JP25248007, K.K.) from JSPS, Japan. A.D.A. would like to thank CNRS for MaD. Y.U.L., J.W.W., and A.D.A. conceived and designed the experiments. A.D.A, B.H.W., and Y.C.J. prepared samples and Y.U.L. performed ellipsometer, prism coupling measurement, and FDTD calculations. Y.U.L., E.G., H.K., and K.K. completed Z-scan measurements. Y.U.L. and K.K. analyzed the Z-scan results. Y.U.L., S.M.C., H.J.K., F.M., I.O., J.C.R., J.W.W., and A.D.A. performed measurement and analysis of molecules orientation and crystallinity. K.J.L., S.Y., and E.C. provided the technical support. Y.U.L., J.W.W., and A.D.A. wrote the manuscript. All authors commented on the manuscript. The authors thank Pohang Accelerator Laboratory (PAL) for giving the opportunity to perform the GIWAXS and NEXAFS measurements. Publisher Copyright: {\textcopyright} 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim",
year = "2018",
month = jul,
day = "18",
doi = "10.1002/adom.201701400",
language = "English",
volume = "6",
journal = "Advanced Optical Materials",
issn = "2195-1071",
publisher = "John Wiley & Sons Inc.",
number = "14",
}