TY - JOUR

T1 - Tunable Diffraction Gratings in Copolymer Network Liquid Crystals Driven with Interdigitated Electrodes

AU - Habibpourmoghadam, Atefeh

AU - Wolfram, Lukas

AU - Jahanbakhsh, Fatemeh

AU - Mohr, Benedikt

AU - Reshetnyak, Victor Y.

AU - Lorenz, Alexander

N1 - Funding Information: Funding by the German Research Council (DFG LO 1922/4-1, DFG GRK 1464) is gratefully acknowledged.

PY - 2019/12/24

Y1 - 2019/12/24

N2 - The diffraction behavior of a polymer network liquid crystal (PNLC) was studied in in-plane switching (IPS) test cells and compared to the behavior seen in a neat liquid crystal. Due to the presence of polymer, the diffraction behavior was varied drastically: PNLCs are composites, which possess a specific domain size. The size of such polymer-induced domains was investigated with polarized optical microscopy and scanning electron microscopy. PNLCs are capable of continuous optical-phase modulation. It was found that electrical addressing with nonhomogenous electric fields can be useful to vary the phase modulation profile as compared to a neat LC. The diffraction patterns seen in a nematic LC were influenced by the applied addressing voltage and showed some limited tunability already. However, in the PNLC, the diffraction patterns were drastically varied as compared to a neat nematic LC. These gratings showed responses localized to the electrodes, had higher tuneability, and could also be useful to partially suppress the zeroth-diffraction order. Depending on the applied voltage, the diffraction efficiency could be tuned, efficiently. The presented results are instructive to understand the impact of a polymer network on the field-dependent reorientation of the liquid crystal director: if addressed with the same electric field profile, the responses were much more localized than in a neat nematic LC. In a straightforward numerical approach, domains in the PNLC samples were described by using cuboids. Diffraction patterns were then calculated based on the director reorientations seen and compared to the experimental data.

AB - The diffraction behavior of a polymer network liquid crystal (PNLC) was studied in in-plane switching (IPS) test cells and compared to the behavior seen in a neat liquid crystal. Due to the presence of polymer, the diffraction behavior was varied drastically: PNLCs are composites, which possess a specific domain size. The size of such polymer-induced domains was investigated with polarized optical microscopy and scanning electron microscopy. PNLCs are capable of continuous optical-phase modulation. It was found that electrical addressing with nonhomogenous electric fields can be useful to vary the phase modulation profile as compared to a neat LC. The diffraction patterns seen in a nematic LC were influenced by the applied addressing voltage and showed some limited tunability already. However, in the PNLC, the diffraction patterns were drastically varied as compared to a neat nematic LC. These gratings showed responses localized to the electrodes, had higher tuneability, and could also be useful to partially suppress the zeroth-diffraction order. Depending on the applied voltage, the diffraction efficiency could be tuned, efficiently. The presented results are instructive to understand the impact of a polymer network on the field-dependent reorientation of the liquid crystal director: if addressed with the same electric field profile, the responses were much more localized than in a neat nematic LC. In a straightforward numerical approach, domains in the PNLC samples were described by using cuboids. Diffraction patterns were then calculated based on the director reorientations seen and compared to the experimental data.

KW - electro-optics

KW - liquid crystal composite

KW - numerical simulations

KW - polymer network liquid crystal

KW - tunable diffraction grating

UR - http://www.scopus.com/inward/record.url?scp=85086631808&partnerID=8YFLogxK

U2 - 10.1021/acsaelm.9b00579

DO - 10.1021/acsaelm.9b00579

M3 - Article

AN - SCOPUS:85086631808

VL - 1

SP - 2574

EP - 2584

JO - ACS Applied Electronic Materials

JF - ACS Applied Electronic Materials

IS - 12

ER -