Optical properties of nematic microlenses doped with chiral nanoparticles

K. Perera; A. Nemati; E. Mann; T. Hegmann; A. Jákli

doi:10.1117/12.2568570

20 August 2020 Optical properties of nematic microlenses doped with chiral nanoparticles

K. Perera, A. Nemati, E. Mann, T. Hegmann, A. Jákli

Proceedings Volume 11472, Liquid Crystals XXIV; 114720O (2020) https://doi.org/10.1117/12.2568570
Event: SPIE Organic Photonics + Electronics, 2020, Online Only

Abstract

Nematic liquid crystals of achiral molecules or racemic mixtures of chiral ones form flat films and show uniform textures between circular polarizers when suspended in sub-millimeter size grids and submersed under water. Recently it was shown that on addition of chiral dopants to the liquid crystal, the films exhibit optical textures with concentric ring patterns with radial variation of the birefringence color, while the films become biconvex. The curved shape together with degenerate planar anchoring leads to a radial variation of the optical axis along the plane of the film, providing a Pancharatnam-Berry type phase lens that dominates the imaging. Here we describe preliminary results of nematic liquid crystal microlenses formed by the addition of chiral nanoparticles. It is found that the helical twisting power of the nanoparticles, the key factor to form the lens, is an order of magnitude greater than that of the strongest molecular chiral dopants. From the observations we present here, we were able to estimate the shape and the geometric focal length of the lens and demonstrated its performance as an optical device. The use of chiral nanoparticles to make microlenses may allow tuning by light that the nanoparticles absorb or, for magnetic NPs, by magnetic fields. Further, the measurement of focal length at known NP concentration offers a new method to measure the helical twisting power of chiral nanoparticles.

Conference Presentation

Citation Download Citation

K. Perera, A. Nemati, E. Mann, T. Hegmann, and A. Jákli "Optical properties of nematic microlenses doped with chiral nanoparticles", Proc. SPIE 11472, Liquid Crystals XXIV, 114720O (20 August 2020); https://doi.org/10.1117/12.2568570

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