Photocontrollable Photonic Crystals Based on Porous Silicon Filled with Photochromic Liquid Crystalline Mixture

Alexey Bobrovsky*, Sergey Svyakhovskiy, Alexey Bogdanov, Valery Shibaev, Martin Cigl, Vĕra Hamplová, Alexej Bubnov

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

Novel photocontrollable photonic crystals based on porous silicon prepared by electrochemical etching are elaborated and their great potential for creation of photoswitchable materials is demonstrated. For this purpose, silicon-based photonic porous wafers are filled with photochromic liquid crystalline (LC) nematic mixture formulated by 4-pentyl-4′-cyanobiphenyl and a specific azobenzene derivative. Results of electron paramagnetic resonance spectroscopy reveal that molecules of LC mixture are aligned along the etched channels in silicon plate, i.e., in normal direction. UV irradiation (375 nm) of the resulting composite causes a shift of photonic band gap to longer wavelengths by ≈10 nm. This phenomenon is explained by isothermal photoinduced nematic–isotropic phase transition associated with the bent-shaped Z isomer formation of the azobenzene compound. During this transition, effective refractive index slightly increases as the initial homeotropic alignment of LC molecules transforms to the isotropic nonaligned state. This process is completely reversible under visible light action (428 nm) and can be repeated many times. Obtained photonic crystal photochromic LC composites can be considered as new promising material for photonic applications.

Original languageEnglish
Article number2001267
JournalAdvanced Optical Materials
Volume8
Issue number22
DOIs
Publication statusPublished - 18 Nov 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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