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

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

Abstract

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).

Keywords

polimeri;nematski tekoči kristali;lasersko mikrostrukturiranje;optika;uklonske mrežice;polymers;nematic liquid crystals;laser micro structuring;optics;diffraction gratings;

Data

Language:	English
Year of publishing:	2021
Typology:	1.01 - Original Scientific Article
Organization:	UL FMF - Faculty of Mathematics and Physics
UDC:	535.421
COBISS:	71504131
ISSN:	2073-4360
Views:	62
Downloads:	24
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	polimeri;nematski tekoči kristali;lasersko mikrostrukturiranje;optika;uklonske mrežice;
Type (COBISS):	Article
Pages:	17 str.
Volume:	ǂVol. ǂ13
Issue:	ǂart. no. ǂ2292
Chronology:	Jul. 2021
DOI:	10.3390/polym13142292
ID:	18209044