Electrically tuneable optical diffraction gratings based on a polymer scaffold filled with a nematic liquid crystal

Bošnjaković, Dejan (author), Fleisch, Mathias (author), Zhang, Xinzheng (author), Drevenšek Olenik, Irena (author)

We present an experimental and theoretical investigation of the optical diffractive properties of electrically tuneable optical transmission gratings assembled as stacks of periodic slices from a conventional nematic liquid crystal (E7) and a standard photoresist polymer (SU-8). The external electric field causes a twist-type reorientation of the LC molecules toward a perpendicular direction with respect to initial orientation. The associated field-induced modification of the director field is determined numerically and analytically by minimization of the Landau–de Gennes free energy. The optical diffraction properties of the associated periodically modulated structure are calculated numerically on the basis of rigorous coupled-wave analysis (RCWA). A comparison of experimental and theoretical results suggests that polymer slices provoke planar surface anchoring of the LC molecules with the inhomogeneous surface anchoring energy varying in the range 5–20 µJ/m$^2$. The investigated structures provide a versatile approach to fabricating LC-polymer-based electrically tuneable diffractive optical elements (DOEs).

• Language: English
• Keywords: polymers, nematic liquid crystals, optics, diffraction gratings, photoresist polymeric materials, laser-based micro structuring, diffractive optical elements
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 17 str.
• Numbering: Vol. 13, iss. 14, art. 2292
• PID: 20.500.12556/RUL-144726
• UDC: 535.421
• ISSN on article: 2073-4360
• DOI: 10.3390/polym13142292
• COBISS.SI-ID: 71504131
• Publication date in RUL: 09.03.2023

Record is a part of a journal

• Title: Polymers
• Shortened title: Polymers
• Publisher: MDPI
• ISSN: 2073-4360
• COBISS.SI-ID: 517951257

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: polimeri, nematski tekoči kristali, lasersko mikrostrukturiranje, optika, uklonske mrežice