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