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EACON 2020

EurAsian Conference on Nanophotonics

Virtual Meeting / October 5 – 7, 2020


Self-assembly of Photo-Switchable Diarylethenes for Optical Microresonator and Arrays

Zhan-Hong Lin | Leibniz Institute of Photonic Technology | Jena, Germany


Photo-switching molecules play an important role in various applications, including optical memory, high-resolution fluorescence imaging, and signal switching. [1] Using photo-switchable fluorophores to make whispering gallery micro-resonator, we can control the ON/Off state of fluorescence while the WGM spectral features are kept and observable  in the on-state. This offers the possibility to configure a rewritable organic memory device with an intrinsic optical fingerprint as a tag for authentication. Here, we demonstrate a rewritable, highly integrated optical memory array by self-assembly of fluorescent Diarylethene (DAE) molecules and the investigation of their optical resonance properties, including lasing action and optical switching properties (Fig.1 a). The compressed microspheres fabricated by solution casting on a substrate show the unique splitting of the WGMs due to the broken symmetry (Fig.1 b), leading to higher Q-factor in comparison with symmetry spherical resonators. [2] This phenomenon can be well reproduced by analytical model and numerical simulations using finite-difference time-domain (FDTD) method (Fig.1 c). Furthermore, the solution of DAE1 was drop-casted onto the hydrophobic/hydrophilic pre-patterned substrate. DAE1 molecules spontaneously aggregate to form the hemispherical micro-disk array on the only hydrophobic pattern (Fig.1 d). Upon the selective irradiation of focused UV/Vis light to the micro-disk array, it can be utilized as an optical memory display with an intrinsic physical unclonable function (UPF).

Figure 1: (a) Molecular structure of DAE1 at closed (1c, left) and open form (1o, right), corresponding to on- and off-state. (b) Splitting WGM spectrum from a oblate sphere assembled by solution casting onto the substrate. (c) Analytically predicted (top), experimental PL spectrum without continuous fluorescence background (middle), and numerically simulated (bottom) peak positions of the splitting WGMs of the spheres with various Rz, ranging from 1,675 (a perfect sphere) to 1,415 nm (an oblate sphere). (d) Two-dimensional array of DAE1 micro hemispheres on a pre-patterned substrate (left) and their fluorescent microscopy image (right). Optical and fluorescence micrographs of the micro hemispheres array. Inset of the left image shows an SEM micrograph of the micro hemispheres array.(Tilt angle: 75°). Inset of the right image demonstrates a “cross“ fluorescence pattern written by UV and Vis lasers.

[1] Masahiro Irie, et al., Chem. Rev. 114, 12174–12277 (2014)
[2] Daniel Braam, et al., Sci. Rep. 6, 19635 (2016)

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Jena | Germany


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