Tilted chiral liquid crystal gratings for efficient large‐angle diffraction

Deflecting light with high efficiency over large angles with thin optical ele- ments is challenging but offers tremendous potential for applications, such as wearable displays and optical communication systems. Compared to the complex production of metasurfaces, the self-organization of liquid crystal (LC) superstructures provides an elegant and flexible way to produce high- quality thin optical components. The periodically varying dielectric tensor in short-pitch chiral LC gives rise to a photonic bandgap, which can be exploited to realize efficient diffractive mirrors in the visible wavelength range. How- ever, large-angle diffractive devices require a small in-plane period, leading to complex self-assembly behavior in the bulk. This work demonstrates that by patterning photoalignment layers at the surfaces with a period comparable to the chiral pitch, the LC self-assembles into a tilted, defect-free helical struc- ture. The director configuration is calculated by finite element simulations and it is experimentally demonstrated that a single photoaligned substrate is sufficient to template the tilted chiral structure in the bulk. This structure effectively (88%) diffracts light over large angles (≈46°) and enables novel micrometer-thin (≈3 μm) optical components that can be produced with an elegant manufacturing process. Due to flexibility of photoalignment, this process could easily be implemented in emerging photonic applications.

Jaar van publicatie:2019

BOF-keylabel:ja

IOF-keylabel:ja

BOF-publication weight:10

Auteurs:National

Authors from:Higher Education

Toegankelijkheid:Open