Electro-optical phase retarders based on newly discovered nematics

Title: Electro-optical devices based on newly discovered liquid crystals

Liquid crystals are composed of rod-like molecules that are aligned parallel to each other. When placed between two transparent electrodes that supply an electric field, the molecules realign, changing the optical contrast of the device. These devices brought a revolution in the industry of flat-panel TVs, computer monitors, and smartphones.

A detrimental property of conventional liquid crystals is that they are not sensitive to the polarity of the electric field, which results in relatively large operating voltages and long switching times (milliseconds). The project focuses on developing new liquid crystal devices in which the molecules show a polar response to the electric field. The goal is to achieve fast (microsecond and faster) optical response driven by weak electric fields.

If successful, the research will fulfill the demands of new technologies, such as artificial intelligence, optical switching, augmented and virtual reality, and deep learning, which require electro-optical devices with a fast microsecond and nanosecond response. A combination of experiments and theoretical analysis will provide a superb opportunity to educate students in advanced electro-optical technologies.

The proposal is to develop electro-optical phase retarders based on the newly discovered liquid crystals such as twist-bend and ferroelectric nematics, which show polar ordering and polar response to an electric field. The goal is to achieve ultrafast nano-and microsecond electro-optic response at operating voltages lower than those used in conventional nematic retarders.

The activity will focus on the design of the device’s substrate to impart a proper alignment of the molecules and then use the electric field to modify their orientation and electric polarity, which would generate a discernable optical response. The research will establish the optimum architecture of retarders, defined by the alignment materials, type of ground-state nematic ordering, the spatial distribution of the electric field, and coupling mechanisms to the electric field.

The electro-optic behavior of devices containing the newly discovered nematics is complex because of multiple pathways of field response, such as bulk and surface polarization, dielectric anisotropy, ionic transport, flexoelectricity, and order electricity overlapped with anisotropic viscosity, elasticity, and anisotropic surface interactions. The project will yield an understanding of how the polar and spatially-modulated molecular arrangements produce an electro-optical response.

The transformative value is in the potential for new design concepts of electrically tunable and switchable optical phase retarders with fast response. A combination of experiments and theoretical analysis will provide a superb opportunity to educate students in advanced electro-optical technologies.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.